clutch slipping
Cargo Master
Joined: Oct 2004
Posts: 2,148
Likes: 0
From: Seneca, SC
The clutch on these trucks is not that hard to do. My biggest recommendation is to remove the transmission from the bell housing before removing the bell housing from the engine to get to the clutch. This makes the removal MUCH LIGHTER. The iron bell housing on these trucks has to weigh close to 50 lbs. This way you can disconnect the linkage from the transmission, remove the driveshaft, support the back of the engine, remove the crossmember, unbolt the transmission, pull the bell housing. Then it's the clutch and flywheel to see definitively what is going on.
If it's been leaking any oil you will end up black from the waist up when you're done, but I've had mine in and out 6 times or so now between engine builds, blown clutches, and broken motor mounts and have it down to four hours or so (by myself) or about half that with a competent buddy.
With the truck sitting that long, the crank shaft may very well have sat on the rear main seal and deformed it. Especially if the seal is old and a little hard. Another dead giveaway is a LOT of oil loss. We're talking about a quart every few hundred miles or worse with no burn off. But the only way to know for sure ( and of course fix it ) is to pull the transmission and clutch and see. This is also one of those fixes that you can save a TON of money on because the rear main is $25 at most, but labor will likely run you $700 at least.
If you do go this route I'd recommend going to NAPA for a new seal, and going with one of their higher dollar ones (15 to 20 dollars instead of 5). If you can't get to one of their regional distribution centers it's worth the wait to send it in. The one that I got was a one piece unit, with a plastic installation tool that slips over the crankshaft and allows you to tap the seal in without rolling the gasket on the edges of the block or the crank. I would heartily caution against getting one of the more common cheaper ones that all of the parts stores seem to have that looks like it's got paint on the outer ring surface of the seal. These were made for when you have the crank out, the pan off, and can use perma tex to create the outer seal. A Quality one for replacement without having to do all that dis-assembly will have a rubber seal on the inner and the outer surfaces of the seal. The one that I put in hasn't leaked a drop since and I was confident at first glance that it didn't need any perma-tex.
If it's been leaking any oil you will end up black from the waist up when you're done, but I've had mine in and out 6 times or so now between engine builds, blown clutches, and broken motor mounts and have it down to four hours or so (by myself) or about half that with a competent buddy.
With the truck sitting that long, the crank shaft may very well have sat on the rear main seal and deformed it. Especially if the seal is old and a little hard. Another dead giveaway is a LOT of oil loss. We're talking about a quart every few hundred miles or worse with no burn off. But the only way to know for sure ( and of course fix it ) is to pull the transmission and clutch and see. This is also one of those fixes that you can save a TON of money on because the rear main is $25 at most, but labor will likely run you $700 at least.
If you do go this route I'd recommend going to NAPA for a new seal, and going with one of their higher dollar ones (15 to 20 dollars instead of 5). If you can't get to one of their regional distribution centers it's worth the wait to send it in. The one that I got was a one piece unit, with a plastic installation tool that slips over the crankshaft and allows you to tap the seal in without rolling the gasket on the edges of the block or the crank. I would heartily caution against getting one of the more common cheaper ones that all of the parts stores seem to have that looks like it's got paint on the outer ring surface of the seal. These were made for when you have the crank out, the pan off, and can use perma tex to create the outer seal. A Quality one for replacement without having to do all that dis-assembly will have a rubber seal on the inner and the outer surfaces of the seal. The one that I put in hasn't leaked a drop since and I was confident at first glance that it didn't need any perma-tex.
Hotshot
Joined: Feb 2004
Posts: 10,867
Likes: 2,626
From: The Shenandoah Valley
1978 F-250 4x4 400M looks like it is leaking oil out of the inspection plate. The oil that is leaking out is black. Really black looks like clutch material. The clutch also slips when going up hill or with any load on it, especially in the rain. I have to keep topping up the Transmission oil so i dont think it is the rear seal. Any ideas?
Originally Posted by me
... etc ...
You have a leaking seal on the transmission input shaft and oil is coming past it and spilling out the front of the tube that the throwout bearing slides on and dripping / spilling into the middle of the pressure plate / clutch and gravity takes it down all over the disc and flywheel and PP surfaces.
You'll need a input shaft seal that fits inside the front plate back near the mating surface where it bolts to the transmission and a clutch disc and some brake clean to clean up the flywheel and PP surfaces. Maybe get them resurfaced just slightly?
Leaks from rear main seals are usually just "messy" as there's a solid flywheel between the rear main seal / leaking oil ... and the clutch surfaces.
You have a leaking seal on the transmission input shaft and oil is coming past it and spilling out the front of the tube that the throwout bearing slides on and dripping / spilling into the middle of the pressure plate / clutch and gravity takes it down all over the disc and flywheel and PP surfaces.
You'll need a input shaft seal that fits inside the front plate back near the mating surface where it bolts to the transmission and a clutch disc and some brake clean to clean up the flywheel and PP surfaces. Maybe get them resurfaced just slightly?
Leaks from rear main seals are usually just "messy" as there's a solid flywheel between the rear main seal / leaking oil ... and the clutch surfaces.
Post Fiend
Joined: May 2009
Posts: 5,054
Likes: 0
From: HOUSTON, TX
Like I said earlier, if the rear main seal is leaking, it WILL cause the clutch to slip ( is it the only problem you might have) NO but one good start to it, because that is one problem associated with a main real seal leak
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