Hey guys,

I'm new to the forum so if I'm doing something incorrectly, sage advice is appreciated. I've got an '86 F350 (T18 Borg Warner) that has a bad transmission shimmy in 1st and reverse gears. The problem is slowly beggining to encroach into 2nd gear. Note, this is only while I am engaging the clutch from a dead standstill. Once the clutch is fully engaged, the shake goes away. The problem has just recently occured. The truck has been in the family for a long time so I am familiar with the service history and I have owned it for several years. Thoughts and theories?

Thanks,

Bo

 

I think the clutch is grabbing. Rough or grabby clutches first show up in the lower gears, and obviously 1st and Reverse are your lowest gears.

It may be that the clutch is worn out. Or, it may be that your rear main seal on the engine is leaking, putting oil on the clutch.

 

Ok. Thanks for the tip. I know that my uncle replaced the clutch less than 15k miles ago, so I doubt it would be that. Is there a way to check for a bad rear seal without dropping the trans? I keep an eye on the oil constantly, giving its old nature and that its a diesel, and I have not noticed any drop in oil lately.

 

I'm not sure about a T18, but most transmissions have an inspection cover that can be removed to check the clutch. That would let you let you determine if there's still lining on the clutch or if there's oil on it.

 

I don't think he has an inspection cover, it is the "block plate" (as referred to here) that goes between the engine and bell housing and covers the full length top to bottom.

 

If the rear seal is leaking it will show at the bottom of the bell housing, & on the ground where you park overnight.

 

Just for your info, if it's all original and a diesel, it will have a t19 not a t18. They are very similar transmissions.

 

Bummer on the lack of an inspection cover. Without that, you really have to at least slide the transmission back to inspect the clutch.

All - Do you agree that it sounds like a clutch problem? Could it be that his style of driving has glazed the clutch? And, did the diesels w/a T19 have a dual-mass flywheel?

 

The older diesels had a regular solid flywheel. Only the zf 5 speed diesels got the DMF. I agree with you Gary, it does sound like some sort of contamination on the clutch disc.

 

Thanks, Dave. I didn't want him pulling the tranny on my suggestion alone.

If the clutch was replaced 15k miles ago then I wouldn't expect it to be worn out. That leaves, as Dave said, some contamination on the clutch, like oil or coolant, or glazing from improper use. In either case you may be able to, at least temporarily, fix that by serious slippage. I've known people who pulled up against a tree and then rev'd the engine enough to not stall and slowly released the clutch to the friction point. A few seconds of that can some times remove a glaze. But too much can warp the flywheel. And if the clutch disk is completely worn out it can ruin the flywheel.

Bo - It is your call on whether to do that or not. I would if I knew the clutch had plenty of lining.

 

I am also drawn to the clutch, something seems amiss there...

 

Alright! Thanks, everyone for the support. I'm going to try out all these tips and get back to you with the result.

Thanks,
Bo