Clutch Slipping

Matthew K

Matthew K

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Broke Engineer
Hello all,

since you guys are so great, and I don't want to spend forever trying to find a car forum that I like:D, I figure I'll ask for your thoughts.

Long story short, I was trying to get my 83' F100 onto ramps today. Easy task right? Not so much. I get everything lined up, start to let the clutch out it grabs some, starts to go up, I let the clutch out more until its all the way out and the engine is still pulling but absolutely no movement. Fairly obvious the clutch is slipping.

The clutch was replaced less then 5k miles ago, and to my knowledge should still have plenty of life left given its use. I understand there could be quite a few reasons that could be causing this, but I'd be interested in knowing what would be the most likely cause. The truck does seem to have a leaking problem, there's oil all over the engine and tranny. I haven't owned the truck for long, but I do intend to fix these problems at least to a degree. So with this, I've heard oil can get onto the plate causing slippage, so my first that is that might be whats causing it. But I'm not sure how to approach fixing that short of replacing all the gaskets.

As I type this I'm reminded that a while back I used this truck to take a boat out, when pulling the boat back out of the water the clutch seemed to have a hard time grabbing then too. I just figured it was the engine being so underpowered, relatively speaking. But it makes sense now. So that contributes more to my thinking that it isn't a bad clutch as it hasn't shown signs of slippage other then these two occasions.
 
Matthew K said:
Hello all,

since you guys are so great, and I don't want to spend forever trying to find a car forum that I like:D, I figure I'll ask for your thoughts.

Long story short, I was trying to get my 83' F100 onto ramps today. Easy task right? Not so much. I get everything lined up, start to let the clutch out it grabs some, starts to go up, I let the clutch out more until its all the way out and the engine is still pulling but absolutely no movement. Fairly obvious the clutch is slipping.

The clutch was replaced less then 5k miles ago, and to my knowledge should still have plenty of life left given its use. I understand there could be quite a few reasons that could be causing this, but I'd be interested in knowing what would be the most likely cause. The truck does seem to have a leaking problem, there's oil all over the engine and tranny. I haven't owned the truck for long, but I do intend to fix these problems at least to a degree. So with this, I've heard oil can get onto the plate causing slippage, so my first that is that might be whats causing it. But I'm not sure how to approach fixing that short of replacing all the gaskets.

As I type this I'm reminded that a while back I used this truck to take a boat out, when pulling the boat back out of the water the clutch seemed to have a hard time grabbing then too. I just figured it was the engine being so underpowered, relatively speaking. But it makes sense now. So that contributes more to my thinking that it isn't a bad clutch as it hasn't shown signs of slippage other then these two occasions.
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nothing wrong with the clutch that replacement won't fix. There is a small chance that something is interfering with the clutch throw but it is a very small chance.
A leaking main seal dumps oil on the clutch and then it slips. Other oil leaks may contribute. Fix the oil leaks then replace the clutch. Or better yet sell the vehicle.
 
I am not familiar with your system, but I think those are cable operated clutches, not hydraulic. Regardless, as noted in a previous post make sure the clutch throw is adjusted correctly - that may be the problem since it doesn't have many miles since the new clutch plate was installed.

If that's not it, sounds like you have oil contaminating the clutch, as you suspect. Fix the leak, replace the clutch plate.
 
Clark1961 said:
A leaking main seal dumps oil on the clutch and then it slips. Other oil leaks may contribute. Fix the oil leaks then replace the clutch.
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On the plus side, the rear main seal is relatively easy to replace once the clutch and flywheel are off.
 
Was going to tell you to just pick up a service manual or a Chilton's since nothing is complicated on an 80s vintage Ford.

But instead Googled to see if I could find enough info without it.

http://www.fordification.com/forum/viewtopic.php?t=66949

That guy has what you need to adjust the throwout bearing. Maybe. Read on.

It is a question someone asked about a 70s vintage one, but other sites talk about the same clutch throwout release rod, and I bet the 80s one if not identical to the 70s one looks so similar that it's nearly the same.

Sounds like a couple of jam nuts adjust the length of the rod if it's a mechanical clutch. Adjusting the length of the rod, you can get the clutch to properly engage fully if it's adjusted wrong. It's probably adjusted such that the clutch is barely engaging, which will burn it up pretty quick.

But... that's only if it's a mechanical clutch.

This guy says 83 was the transition year they switched from mechanical to hydraulic clutches.

So we'd need to know what you actually have.

Reading that old stuff reminded me of the other problem with Fords of that vintage. You need a special rod to stick into the manual transmission before you drop it down, or the stupid bearings will fall down inside of it. I think.

Anyway. A good manual plus making sure you know which engine and transmission combo you have, will go a long way.

When you say you've only owned it 2 months and the clutch was replaced 5K miles ago, was that you or did the previous owner say they did it?

I suspect they adjusted the whole thing wrong. I hope they didn't lie to you about the condition of the clutch.
 
denverpilot said:
Was going to tell you to just pick up a service manual or a Chilton's since nothing is complicated on an 80s vintage Ford.

But instead Googled to see if I could find enough info without it.

http://www.fordification.com/forum/viewtopic.php?t=66949

That guy has what you need to adjust the throwout bearing. Maybe. Read on.

It is a question someone asked about a 70s vintage one, but other sites talk about the same clutch throwout release rod, and I bet the 80s one if not identical to the 70s one looks so similar that it's nearly the same.

Sounds like a couple of jam nuts adjust the length of the rod if it's a mechanical clutch. Adjusting the length of the rod, you can get the clutch to properly engage fully if it's adjusted wrong. It's probably adjusted such that the clutch is barely engaging, which will burn it up pretty quick.

But... that's only if it's a mechanical clutch.

This guy says 83 was the transition year they switched from mechanical to hydraulic clutches.

So we'd need to know what you actually have.

Reading that old stuff reminded me of the other problem with Fords of that vintage. You need a special rod to stick into the manual transmission before you drop it down, or the stupid bearings will fall down inside of it. I think.

Anyway. A good manual plus making sure you know which engine and transmission combo you have, will go a long way.

When you say you've only owned it 2 months and the clutch was replaced 5K miles ago, was that you or did the previous owner say they did it?

I suspect they adjusted the whole thing wrong. I hope they didn't lie to you about the condition of the clutch.
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As far as ownership part goes, this truck was owned by a family member who restored it(not including engine/tranny stuff) so I'm adept at what maintenance has been done in the last 10ish years.

As for type of clutch I "believe" it is a mechanical clutch. I've never seen a fluid reservoir in the very spacious engine bay, but I've never specifically looked for it. I'll check to make sure today that it is in fact a mechanical. One thing I do know, it appears the 83' model came with a mechanical and then a hydraulic clutch. As both are available to buy, and it is only the 83' year model they offer two different clutches.
 
Sounds to me like the rear main seal on the engine (crankshaft) is shot. Less likely is the input shaft seal on the transmission, but it can happen.
 
From your description it sounds more like the clutch has gotten oiled rather than the linkage is not letting the clutch engage. On a front engine/rear drive vehicle dropping the transmission and replacing the clutch isn't too bad of a job, provided you can get the vehicle high enough to work on it comfortably and you have some way of jacking the transmission down and then back up. However, you'll have to figure out what's causing the oil leak and repair that or else you'll be doing this all over again in six months. Once you remove the transmission, chances are what you're going to see is oil all over the place and it won't be at all obvious where it's coming from, and that's where a professional mechanic's expertise comes in handy.
 
Was the pressure plate changed? 25 year old springs do get weaker.
 
Agree w rear main seal leakage as a likely possibility.
 
Any smoke coming from under the truck.??

Or a burning smell.??

I can't remember what an 83 Ford pickup looks like.
 
Zeldman said:
Any smoke coming from under the truck.??

Or a burning smell.??

I can't remember what an 83 Ford pickup looks like.
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Burning smell only in scenarios like yesterday where it was slipping a bunch.

Que internet picture that features the same color as mine
1983-ford-f150-1.jpg

url
 
Wow... that is a nice looking truck.!!

Ok, burning smell so definitely something going on.

Oil all over the tranny and engine is my first thought. I am thinking valve cover gasket leak would be the cause of oil all over the top.

Rear main seal oil would drip off the bottom of the engine/transmission.

Hopefully the previous owner replaced the pressure plate and throw out bearing as well. It is a 3 speed or 4 speed? V8 engine or straight 6?

First as others have mentioned would be to check the adjustment. You tube could be helpful for learning that. it's not hard. Usually a first timer will go the wrong way with the adjustment. Don't ask how I know that....

If the clutch plate is oil soaked, replacement will be the easiest solution. I have tried cleaning clutch plates but that is usually a temporary solution.
 
Zeldman said:
Wow... that is a nice looking truck.!!

Ok, burning smell so definitely something going on.

Oil all over the tranny and engine is my first thought. I am thinking valve cover gasket leak would be the cause of oil all over the top.

Rear main seal oil would drip off the bottom of the engine/transmission.

Hopefully the previous owner replaced the pressure plate and throw out bearing as well. It is a 3 speed or 4 speed? V8 engine or straight 6?

First as others have mentioned would be to check the adjustment. You tube could be helpful for learning that. it's not hard. Usually a first timer will go the wrong way with the adjustment. Don't ask how I know that....

If the clutch plate is oil soaked, replacement will be the easiest solution. I have tried cleaning clutch plates but that is usually a temporary solution.
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Yea I'm thinking valve cover is definitely at least one source of the leaking oil. Engine: Ford 300(4.9l) Straight 6 with a 4 speed manual. I'll have to ask the previous owner if he has the repair list to be certain, but the clutch was installed by a shop, not by the owner themself so not 100% of what they replaced besides the clutch itself.
 
Ok, the 300 valve cover gasket really makes a mess when they leak, but the leaking oil usually doesn't make it to the clutch plate.

Another thought I had was the clutch plate was put in backwards (again, don't ask how I know) but a good shop would not do that.

On the pedal, there should be about an inch to two inches of free travel before you feel any pressure. That is if it is a mechanical clutch.

It could also be a broken spring(s) in the pressure plate. That would allow the plates to slip.
 
Zeldman said:
Any smoke coming from under the truck.??

Or a burning smell.??

I can't remember what an 83 Ford pickup looks like.
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I had an 84. The 83 looked like it for the most part.
 
Zeldman said:
Ok, the 300 valve cover gasket really makes a mess when they leak, but the leaking oil usually doesn't make it to the clutch plate.

Another thought I had was the clutch plate was put in backwards (again, don't ask how I know) but a good shop would not do that.

On the pedal, there should be about an inch to two inches of free travel before you feel any pressure. That is if it is a mechanical clutch.

It could also be a broken spring(s) in the pressure plate. That would allow the plates to slip.
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I had the broken spring thing. I knew pretty much instantly what the problem was. That slip was smoother than oil on the pressure plate slip.
 
80-86 Fords are known as Bullnose trucks because of the way the headlight bezels look. I have an '86 4.9 with a hydraulic clutch, shorty bed like yours but in red. Look for a little hydraulic reservior on the drivers side firewall. Having said that, if the mc were shot, the clutch would still engage fully, just not disengage. If the throwout bearing were shot, you'd hear it with the clutch disengaged. Usually with oil on the plate, you'll get some kind of chatter. My guess is there's a new clutch, pressure plate, throwout bearing and flywheel resurface in your future. Parts are cheap, and if you have a floor jack it's not a bad job to do yourself.
 
The rear main seal is a one piece seal, so the when you do the clutch do that at the same time.
 
FormerHangie said:
From your description it sounds more like the clutch has gotten oiled rather than the linkage is not letting the clutch engage. On a front engine/rear drive vehicle dropping the transmission and replacing the clutch isn't too bad of a job, provided you can get the vehicle high enough to work on it comfortably and you have some way of jacking the transmission down and then back up. However, you'll have to figure out what's causing the oil leak and repair that or else you'll be doing this all over again in six months. Once you remove the transmission, chances are what you're going to see is oil all over the place and it won't be at all obvious where it's coming from, and that's where a professional mechanic's expertise comes in handy.
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This. The clutch has gotten oiled.

But I'm not so sure about the rear seal theory advanced by others. A leak there is unlikely to get "oil all over the engine ... " If it's a Six, the leak may be as simple as the valve cover gasket. But there are lots of potential perps, even a less-than-tight oil filter.
 
Just to address earlier questions, this truck is indeed a cable operated clutch, not hydraulic.
 
Chip Sylverne said:
80-86 Fords are known as Bullnose trucks because of the way the headlight bezels look. I have an '86 4.9 with a hydraulic clutch, shorty bed like yours but in red. Look for a little hydraulic reservior on the drivers side firewall. Having said that, if the mc were shot, the clutch would still engage fully, just not disengage. If the throwout bearing were shot, you'd hear it with the clutch disengaged. Usually with oil on the plate, you'll get some kind of chatter. My guess is there's a new clutch, pressure plate, throwout bearing and flywheel resurface in your future. Parts are cheap, and if you have a floor jack it's not a bad job to do yourself.
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Don't bother with resurfacing the flywheel...it's generally not needed.
 
Replace valve cover gasket, remove transmission, clutch ,pressure plate and throuwout bearing. Remove flywheel and clean the back of the engine. Replace rear main seal. Inspect and clean flywheel. If the flywheel is showing blue spots or chatter marks either have it resurfaced or replace with a new one. New is not all that expensive. Install a new clutch KIT . Done now have a beer.
 
Adjust that clutch cable first. The guys that replaced the clutch didn't leave enough free play, and as the clutch wears, the free play disappears and the mechanism starts holding the pressure plate off the clutch plate and you get slippage. They might have left no free play at all when they did the job.

Oil on a clutch usually causes a lot of shuddering when the clutch is engaging.
 
Dan Thomas said:
Oil on a clutch usually causes a lot of shuddering when the clutch is engaging.
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Assuming that is true, there was no shuddering with this clutch slippage. Just the truck staying still and the engine sounding like it was under load.
 
This is most likely a separate issue, but sometimes when coming to a stop, when I try to put the truck into first gear, it will go into something like a false neutral. Like I put it in 1st gear, let out the clutch and it doesn't move. Press in the clutch, pull out of gear, put it back in and then the truck moves.
 
There are some "gates" or bushings in the shifter that get worn and can cause difficulty shifting gears. Not likely relsted to the clutch. If I try and quickly shift from 2nd to third, I get the same thing you do. The shifter comes out through the top of the transmission by removing the cover boot and a plate. First, just try slowing down your shifting motion. If that doesn't work, it'll need to be addressed. Again, you can do it yourself. These old trucks are pretty easy to work on. When you say the engine is under load but the truck doesn't move, are you sure your parking brake isn't stuck?
 
Chip Sylverne said:
When you say the engine is under load but the truck doesn't move, are you sure your parking brake isn't stuck?
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That was referring to my experience trying to get the truck on ramps, and yes, I'm sure that the brake wasn't on/stuck. Once I put the clutch back in, it would roll backwards.
 
Sidenote: The reason I was putting the truck on ramps was to get to the exhaust system. There's been a rattling noise coming from it, thought it was the catalytic converter, nope, the muffler. I removed everything from the catalytic converter back, as all of it was pretty rusty and I want to install a new one. I drove the truck today with all the stuff off(header and pipe going to ground is still on) and it literally sounds like a semi truck right now :D
 
The Ford 300-6 is a pretty stout engine. We had one in a '75 F-250 Van. At an auction we found a 4 bbl intake manifold and a split exhaust hedder. We called a camshaft manufacturer and got a stout street cam. We assembled the motor with the hot rod pieces, then put a 4:10 rear gear in it. It actually ran really well. Later on we put a 5 speed tranny out of a Mustang in it, with a little adjustment to get it to fit.

Everyone was really surprised a 6 cylinder could run so well. I used it to pull my dirt track car for two seasons.
 
Zeldman said:
The Ford 300-6 is a pretty stout engine. We had one in a '75 F-250 Van. At an auction we found a 4 bbl intake manifold and a split exhaust hedder. We called a camshaft manufacturer and got a stout street cam. We assembled the motor with the hot rod pieces, then put a 4:10 rear gear in it. It actually ran really well. Later on we put a 5 speed tranny out of a Mustang in it, with a little adjustment to get it to fit.

Everyone was really surprised a 6 cylinder could run so well. I used it to pull my dirt track car for two seasons.
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Exactly what I did to mine. Bored .030 over,ported and port matched the head, Offenhauser heated dual plane manifold with Holley 450 CFI 4bbl, Clifford split header, an RV cam and dumped the Ford TFI ignition for a GM 4 prong. Runs great, only problem it it keeps breaking motor mounts from the torque if I get on it off the line.

I like old school stuff.
 
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Truth be told, the Ford 300 I6 is arguably one of the best they ever made. Tons of torque just like most other inline-engines, and it's just about impossible to kill them, they were just built strong. I'd probably posit the 302/351w motors as being the "best" in terms of most impactful, but the 300-6 beats even the sturdy 302 in durability.
 
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Bill Jennings said:
The Chrysler 225 slant six was another good old straight 6 engine, very tough. The early models sans emissions equipment ran great.
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A friend used to drag race a street legal Duster with a modified 225. I think it ran low 11s in the 1/4 mile. Then one day it swallowed a valve. Then he brought out the 330 Desoto Hemi and put it in.
 
Zeldman said:
The Ford 300-6 is a pretty stout engine. We had one in a '75 F-250 Van. At an auction we found a 4 bbl intake manifold and a split exhaust hedder. We called a camshaft manufacturer and got a stout street cam. We assembled the motor with the hot rod pieces, then put a 4:10 rear gear in it. It actually ran really well. Later on we put a 5 speed tranny out of a Mustang in it, with a little adjustment to get it to fit.

Everyone was really surprised a 6 cylinder could run so well. I used it to pull my dirt track car for two seasons.
Click to expand...

Chip Sylverne said:
Exactly what I did to mine. Bored .030 over,ported and port matched the head, Offenhauser heated dual plane manifold with Holley 450 CFI 4bbl, Clifford split header, an RV cam and dumped the Ford TFI ignition for a GM 4 prong. Runs great, only problem it it keeps breaking motor mounts from the torque if I get on it off the line.

I like old school stuff.
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Any idea how much power either of these adds? I'd be interested in giving it some more "life". It just seems to be very lacking in hp. Which is reasonable since it came factory with a little over 100hp. Also, what mpg do/did you all get? I average about 14-14.5mpg.
 
Matthew K said:
Any idea how much power either of these adds? I'd be interested in giving it some more "life". It just seems to be very lacking in hp. Which is reasonable since it came factory with a little over 100hp. Also, what mpg do/did you all get? I average about 14-14.5mpg.
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With my 300-6 I got 9-10 MPG before we added on a few parts. After adding the fun stuff along with the 5 speed tranny I could get about 12 MPG in town if I drove it normally. Remember it was a full size 1975 3/4 ton van. I think it averaged 9 MPG pulling the trailer. One thing to take in account is this was 30-32 years ago. The national speed limit was 55 MPH. It was fun to drive, I could actually pull out to pass while pulling the race car trailer. As for horse power I could not even guess.

A few things we did was take off the radiator fan and add an electric fan. I also added a second alternator on the rear axle, and it had two batteries. We also did a port matching on the head and intake and put in bigger valves along with a 5 angle valve job. And we added harder valve seats for the unleaded gas. We also CC'ed the combustion chambers just for practice. We also balanced the rotating assembly just for practice as well. For the cam we called Iskey Cams and gave them the information and they ground a cam for us to meet out needs. (wants) It really worked good.

It was fun to drive. Chevy and Ford pickups were pretty anemic at that time and that big van could keep up with them. Some of the rednecks would get really ****ed off to see a 6 banger keeping up with them...:lol::lol::lol:
 
Matthew K said:
Any idea how much power either of these adds? I'd be interested in giving it some more "life". It just seems to be very lacking in hp. Which is reasonable since it came factory with a little over 100hp. Also, what mpg do/did you all get? I average about 14-14.5mpg.
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A lot. It adds a lot. Didn't dyno it, but the guy who did my state inspection builds hot rods, and his response was "you got that thing runnin' good". I can rev it to 6k RPM, but anything over 3k all your making is noise, the power curve goes pretty flat above that.
The head was milled a bit, and the chambers cc'd. My compression ration is about 10:1. I didn't go with a super high-lift cam for streetability, it was just an off the shelf Comp RV cam and I installed stiffer springs. Porting the head helped a lot. I have the cam tag somewhere around here if you're really interested. The Holley has vacuum secondaries, so it runs pretty much off the 2bbl and bottom half of the intake unless I put my foot down. The hardest part was tuning out a cold stumble. The stock intake uses exhaust gas to heat the intake plenum right away for better fuel vaporization. With the header, that goes away, so you need to heat the plenum floor with a hot engine coolant. I fabricated and aluminum hot plate that bolted to underneath the aluminum intake manifold. Works good. The exhaust was bumped up to 2 1/2 inch diameter pipe for better flow out the side.

I also ditched the ignition system for an Duraspark II that I could re-curve for a little more advance.
I get a little over 14mpg around town, 16 highway. But if I get to feeling sporty, I can watch the fuel guage bend to the left pretty quick.
The guru's for building these 300's are at fordsix.com. There's a guy over there who drags races one, gets 350hp out of it.
 
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