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Front drive shaft yoke wiggles
Posted: Sun Mar 05, 2023 6:32 am
by 67D100Pickup
I have a D100 with a 745A transmission, single drive shaft.
We feel vibration that gets worse with speed. We ran the truck on jack stands and could see the front of the drive shaft yoke wiggling in the rear transmission extension. And it leaks there.
What would cause that? I had the transmission rebuilt about 2000 miles ago and installed a new clutch with refinished flywheel but the machinist that turned the flywheel did it crooked. The clutch-side machined plane was almost .006" out of parallel with the crankshaft mount side.
I didn't know what was wrong - I'm not a mechanic - but the machine "lurched" violently during clutch engagement. 2000 miles later I got around to inspecting and discovered the flywheel was out of parallel. I got that fixed, now I see the yoke wiggles inside the rear extension causing the vibration.
I don't want to replace the rear bearing and seal and have the vibration and leaking recur so I wanted to check with y'all first...
Would the screwed up flywheel/clutch cause the bearing/seal failure all the way in the back of the tranny? Of so I can just replace the rear bearing and seal again, yes? If not, what else could have caused the bearing failure? Crooked driveshaft or yolk?
--Jeff
Re: Front drive shaft yoke wiggles
Posted: Sun Mar 05, 2023 10:08 am
by 712edf
Any source of vibration, be it an out of balance issue or alignment problem, has the potential to eventually damage a bearing.
I cracked/broke a few 727 tailshaft housings due to having the wrong harmonic balancer on a big block that vibrated noticeably at certain RPM's.
Bucky
Re: Front drive shaft yoke wiggles
Posted: Sun Mar 05, 2023 10:11 am
by 712edf
And yes bent or misaligned components would contribute too.
Bucky
Re: Front drive shaft yoke wiggles
Posted: Mon Mar 06, 2023 9:43 pm
by nutz
would think a bad u-joint (remove drive shaft and see if its tight)
or bent drive shaft
take a piece of caulk put it on the end of a stick
and with a the drive shaft spinning very slowly and lightly try and touch the spot where it comes out of trans ,and the end of the drive shaft
to see if it has a high spot (bent)
Re: Front drive shaft yoke wiggles
Posted: Mon Mar 06, 2023 11:13 pm
by PwrWgnDrvr
nutz wrote: ↑Mon Mar 06, 2023 9:43 pm
would think a bad u-joint (remove drive shaft and see if its tight)
or bent drive shaft
take a piece of caulk put it on the end of a stick
and with a the drive shaft spinning very slowly and lightly try and touch the spot where it comes out of trans ,and the end of the drive shaft
to see if it has a high spot (bent)
chalk, not caulk, right?
You could use caulk, but it would make a hella mess!
Re: Front drive shaft yoke wiggles
Posted: Tue Mar 07, 2023 1:50 am
by 67D100Pickup
PwrWgnDrvr wrote: ↑Mon Mar 06, 2023 11:13 pm
nutz wrote: ↑Mon Mar 06, 2023 9:43 pm
would think a bad u-joint (remove drive shaft and see if its tight)
or bent drive shaft
take a piece of caulk put it on the end of a stick
and with a the drive shaft spinning very slowly and lightly try and touch the spot where it comes out of trans ,and the end of the drive shaft
to see if it has a high spot (bent)
chalk, not caulk, right?
You could use caulk, but it would make a hella mess!
Yes, I think I'll try it with chalk first
Re: Front drive shaft yoke wiggles
Posted: Tue Mar 07, 2023 10:00 pm
by nutz
yeah
then again i might be nutz
Re: Front drive shaft yoke wiggles
Posted: Wed Mar 08, 2023 8:47 am
by Wildergarten
nutz wrote: ↑Tue Mar 07, 2023 10:00 pm
then again i might be nutz
The most common cause of a shuddering jackshaft is worn splines, which would have to be welded in. That would mean a new shaft.
Re: Front drive shaft yoke wiggles
Posted: Thu Mar 09, 2023 9:33 pm
by nutz
shouldn't that have the slip spines in the trans ?
not saying could still be worn
oh and if the pinion angle if off could induce vib in your drive shaft
Re: Front drive shaft yoke wiggles
Posted: Fri Mar 10, 2023 12:58 am
by Wildergarten
nutz wrote: ↑Thu Mar 09, 2023 9:33 pm
shouldn't that have the slip spines in the trans ?
As I recall from the 1964 A904 I had, the splines were inside the yoke which turned in an oilite bushing.
The A727B I just sold had a similar arrangement. But I was mixing up my driveshafts in thinking about the problem.
Sorry about that. I probably shouldn't post on burn days, as I'm usually exhausted.
Re: Front drive shaft yoke wiggles
Posted: Fri Mar 10, 2023 9:36 pm
by nutz
ha thats every day for me anymore
Re: Front drive shaft yoke wiggles
Posted: Wed Mar 15, 2023 12:25 pm
by 67D100Pickup
67D100Pickup wrote: ↑Sun Mar 05, 2023 6:32 am
I have a D100 with a 745A transmission, single drive shaft.
We feel vibration that gets worse with speed. We ran the truck on jack stands and could see the front of the drive shaft yoke wiggling in the rear transmission extension. And it leaks there.
What would cause that? I had the transmission rebuilt about 2000 miles ago and installed a new clutch with refinished flywheel but the machinist that turned the flywheel did it crooked. The clutch-side machined plane was almost .006" out of parallel with the crankshaft mount side.
I didn't know what was wrong - I'm not a mechanic - but the machine "lurched" violently during clutch engagement. 2000 miles later I got around to inspecting and discovered the flywheel was out of parallel. I got that fixed, now I see the yoke wiggles inside the rear extension causing the vibration.
I don't want to replace the rear bearing and seal and have the vibration and leaking recur so I wanted to check with y'all first...
Would the screwed up flywheel/clutch cause the bearing/seal failure all the way in the back of the tranny? Of so I can just replace the rear bearing and seal again, yes? If not, what else could have caused the bearing failure? Crooked driveshaft or yolk?
--Jeff
Just for closure... I took the drive shaft to a specialist, Precision Drive in OKC. Their equipment said the shaft was bent and out of balance. I assume someone drove over something they shouldn't have sometime in the truck's long colorful past.
Anyway, they returned it straight and balanced and the vibration is gone.
Now... Where is my time and money needed next...
--Jeff
Re: Front drive shaft yoke wiggles
Posted: Wed Mar 15, 2023 5:04 pm
by 712edf
Excellent!
It always feels good to get something corrected. Hopefully nothing new will pop up.
Bucky
