TH200-4R rear seal leak after sticky TV

[Raxo]

I was driving along at 50 mph and while accelerating a bit I felt that the car was more eager than usual. I figured it was still in 3rd gear. I came to a stop, checked the TV cable adjustment and started to drive. Second and third gear engaged at much higher rpms and 4th didn't engage at all. A bit more stop and go driving and finally it didn't go into second gear.

So I picked up some speed in first gear and then rolled in neutral, I didn't want to even moderately rev in first gear all the way.

I finally got home and worked the TV cable several times - pulled it out, let it back in (I wish I had thought of that on the road). Luckily it started shifting again, although accompanied by a light shudder on some revs.

Then I noticed the rear seal leak on the trans. Could that be a result of the sticking throttle valve? It definitely didn't leak before. I don't have to drive much to get the oil dripping.

How much should the machined part of the yoke stick out from the rear seal?

Too much? That's the cause of the shudder?

 

[Raxo]

I honestly can't remember if it was like that in the past. When I saw that today I instantly realized that something isn't right. Then again, I've had this car for two years now and haven't had a problem with the rear seal or the driveshaft.

If anyone can provide me with B-body (make and model in the signature) driveshaft measurements, then I can confirm if it's the right size or not.



And yes, maybe I shouldn't be allowed to work on cars. I'm actually getting fed up with it. I just want to enjoy a sunny day from my comfortable bench seat, accompanied by a V8 rumble and some good tunes.

 

[Raxo]

too short driveshaft?

You are right. Now tell me, how can I pull this sucker out about 2 inches?

 

[KL Mallender]

Hi Raxo, to be honest I dont recognise that type of driveshaft being used in the full-size car line, but I could very well be wrong. The proper length shaft/yoke assembly will just barely allow you to clear rear axle flange when installing(especially if axle is at full drop). I believe the procedure of selecting drivesaft length is to install trans slip yoke completely(bottom it out) then pull out 1-1/2 inches, then measure the center to center of trans yoke and rear axle flange with axle at loaded ride height,(which would represent maximum axle arc travel)
Good luck.

Kevin.

 

[Raxo]

That driveshaft worked fine for two years or so, so it could be the original one.

The differential end of the driveshaft is coupled to the tube by rubber. Some sort of vibration damper? Is that the only thing that's holding those two together?

The rear axle and the engine mounts are fine and where they're supposed to be, so this joint is the only option.

That rear seal leak is caused by the wiggly driveshaft. But now, since the yoke won't even reach the bushing, it's even worse.

 

[KL Mallender]

GM may have very well used that type of damper for the full size cars, I just dont remember, reguardless, that shaft should NOT be used further, also double check tailshaft bushing and seal for damage(the yoke might have pushed the bushing inward and might no longer support shaft properly. There is a "specialty" tool to remove and replace bushing in-car if necessary, a local transmission shop should have one. Good luck.

Kevin.

 

[Pronto]

Not sure about the full size Buicks but it looks like the driveshaft should be in to where that polished area is. Messing with the TV cable didn't do that. BTW. the output shaft is "wiggly" on the 200r when you pull out the driveshaft.

 

[Raxo]

that shaft should NOT be used further

What about stretching it to correct length somehow and then welding it so it couldn't move away any more? Not recommended?

It can go out of balance for sure...

 

[KL Mallender]

I would not recommend welding any driveshaft due to stress risers from weld, but if you can "stretch" it to allow for proper trans/yoke engagement you could take exact measurement for proper replacement whether new or used, lots of forces being handled by a "simple looking" shaft, respect that it can cause untold damage if it stops enjoying it's job. I would think a good salvage yard could fix you up for a just a couple of bucks, sometimes free if you throw them some old junk you might have lying around, not that I would ever have "stuff" stashed in the corner of the garage, or shed, or basement, or attic, or my favorite hiding place, up my ass right next to my head, LOL :biggrin:

Kevin

 

[Raxo]

not that I would ever have "stuff" stashed in the corner of the garage, or shed, or basement, or attic, or my favorite hiding place, up my ass right next to my head, LOL :biggrin:

I'll try to find a replacement. But even used parts aren't cheap in this part of the world.

 

[Raxo]

to be honest I dont recognise that type of driveshaft being used in the full-size car line, but I could very well be wrong.

What type is used then? Without the damper?

I was thinking of letting a shop remove that damper, weld the driveshaft to the correct length and then balance it.

 

[Raxo]

I was thinking of letting a shop remove that damper, weld the driveshaft to the correct length and then balance it.

Done. Not cheap though :biggrin: