66 TH400 tail shaft bushing

[scotth3886]

Now that the weather is clearing/warming to the point that I don't have to worry about road salt, back to some issues from last year that I wasn't able to get completely fixed.

Biggest one is the harmonic vibration that's road speed related, not engine speed.  Vibration was bad enough that at 75 and up it sounded/felt like something was going to come apart.  We did the front centering kit and two u-joints and rebalanced the drive shaft.   That mostly fixed the issue.  We didn't do the rear joints because they felt fine and I couldn't find another centering kit.  Did the output shaft seal because it was leaking pretty badly.  Leak has stayed fixed.  I didn't do the tailshaft bushing because I couldn't find any the right size.

Audible issue is pretty well fixed up past 90 mph, but I still feel a granularity (for lack of a more descriptive term) that isn't right for a Fleetwood at today's freeway speeds.  Something still isn't quite right yet. 

Over the winter, found some more seals and bushings that are supposed to be correct from Fatsco.  The issue: the driveshaft yoke is 1.58" OD and the bushings seals they sent me are 1.68" ID.  Doesn't this seem a little loose for the bushing?  Took the parts up to the mechanic today to get some good measurements and he thinks they're too loose.  If the OD of the driveshaft yoke is 1.58", shouldn't the ID of the bushing be somewhere around 1.61 or 1.62"?   

Second issue is: does anyone know who would have centering kits for the cardan joints?  I've checked Rockford and everyone else who I can think of. 

Thanks in advance for your help. 

[scotth3886]

Is a .10" too loose between yoke and bushing?

[scotth3886]

I just talked to Fatsco again and they said that's the bushing and they've sold hundreds, maybe thousands for that application.  Oh well, I'll give it a try.

[bcroe]

All TH400 output shafts have the same spline size, but in early years I have
seen some with a smaller yoke outer diameter.  The yoke of course is matched
to the seal, output bushing, and trans tail cover. 

If some of the smaller dia parts went not available, you could change out the
above set and convert to the larger size, I have done that to standardize
everything here.  It can be done without removing the trans from the car, but
of course a different yoke is used and tail housing. 

A bad bushing would tend to take out the seal before long.  Bruce Roe

[scotth3886]

All TH400 output shafts have the same spline size, but in early years I have
seen some with a smaller yoke outer diameter.  The yoke of course is matched
to the seal, output bushing, and trans tail cover. 

If some of the smaller dia parts went not available, you could change out the
above set and convert to the larger size, I have done that to standardize
everything here.  It can be done without removing the trans from the car, but
of course a different yoke is used and tail housing. 

A bad bushing would tend to take out the seal before long.  Bruce Roe

That's what happened.  We replaced the seal which took car of the leak, but couldn't find the bushing. 

I take it in April 5th so I'm going to try the bushing that Fatsco says is the one.  Yoke is 1.58" OD and bushing is 1.68"ID.  Seems too loose, but I'll give it a shot. 

Little by little I'll get through the issues. 

Thanks

I'll try to modify this previous post.  The new CLC forum spam blocker is blocking me so I can't post new posts until its fixed

[Roger Zimmermann]

I have the impression that the diameter from the new bushing is too large. 0.1" play, it's not sound. Before you take the original bushing out, check the inside diameter. It may be less than 1.68"...

[bcroe]

This does not sound right to me.  Are you sure it is a TH400, with a vacuum
modulator?  The later yokes were all about 1.89 in dia, and I am pretty sure
the early small ones were about 0.2 smaller, 1.69 in.  1.58 in is not right. 

Bruce Roe

[The Tassie Devil(le)]

All TH400 output shafts have the same spline size, but in early years I have seen some with a smaller yoke outer diameter.  The yoke of course is matched to the seal, output bushing, and trans tail cover.     Bruce Roe 

I am not sure about 1966, but the TH400 is made with two different sizes of Yoke.   The normal ones are for the lower cars with the Short output shaft, and the Cadillac with the Cardan Joints have used a larger one.   This Trans uses an extended rear housing with longer output shaft

Bruce.

[The Tassie Devil(le)]

Scott has asked me to advise everyone that until the current problems that the Forum is encountering, he cannot post messages, and apologises for not being able to respond when folks are trying to help me.

As soon as he can gain access, he will respond.

Hopefully this will be sorted out soon, and we can get back to normal.

Bruce.

PS.   One of the problems with upgrading, and with so many people using different ways to access the internet.

[bcroe]

Ha Ha, I must convert from Metric!  Thanks for the pictures.  The 47.95 mm is
the 1.89 in I mentioned, the 43.2 mm is the smaller 1.70 in, a little more
accurate than my 1.69 in memory. 

Both of these are not 1.58 in, just where does that come from?

In every case the size of the splines on the output shaft is the same.  I do not
know what choices Cadillac made in 1966, but either diameter yoke has been
used in either short or long tail extension housings.  For either length, it is
possible to change to the other dia yoke by changing the extension housing
with its different dia seal and bushing, without removing the trans from the car. 

There were 4 in, 9 in, and 13 in tail extension housings, but that is not the
problem here.  It is necessary to completely dis assemble the trans to change
the shaft to a different length. 

There is also the difference of yokes that just slide over the splines, and yokes
which have a long unsplined outer tube that extends farther in, to seal on an O
ring on the output shaft.  These yokes have a center air vent.  If used on a
shaft without the O ring, oil will come out the vent.  The short yoke has no vent,
and will work with either style shaft.  Bruce Roe

[savemy67]

Hello Scott,

When I rebuilt my '67 TH400, it had two bushings in the extension housing.  The rebuild kit I got from Fatsco had one bushing, so I ordered a second.  The attached photos show the new bushings (wider/longer) along side the old, original bushings, as well as the fit of the new bushings on the driveshaft yoke.

If your measurements are correct, .100" difference is way too much clearance between the OD of the yoke and ID of the bushing.  The bushing(s) will "crush" a little upon installation, but no where near .100".

In my case, the bushings fit fine over the yoke before installation, with a few thousandths clearance (approx .004").  When the bushings were installed in the extension housing, the yoke would barely rotate, so I honed the ID of the bushings until I was satisfied with the fit.

As Bruce Roe and Roger mentioned, .100" is too much clearance, and is likely to lead to premature failure of the seal.  Transmission bushings should have less than .010" clearance as they function to hold rotating shafts in alignment.  As Bruce Reynolds mentioned, Cadillacs had a unique extension housing in their Hydra-Matics for many years.  Is it possible your car is not fully original?

Respectfully submitted,

Christopher Winter

[scotth3886]

Sorry folks.  The new spam blocker blocked me out.  I had to change email addresses to get this to work again.

[scotth3886]

This does not sound right to me.  Are you sure it is a TH400, with a vacuum
modulator?  The later yokes were all about 1.89 in dia, and I am pretty sure
the early small ones were about 0.2 smaller, 1.69 in.  1.58 in is not right. 

Bruce Roe

Bruce,

I replaced the vacuum modulator last week and fixed a long time vacuum leak.  I replaced the twin pitch kick down switch not long after I got the car.  The two wires are coming out of the side of the transmission as it should be on a 64-67.  Sure seems like a TH400.  There's no 4th gear or TV cable so it's not a TH700.  The guy from Fatsco (Don) said 1.58 is correct for the 1.68" bushing.  ( I was mistaken.  I went back again to look at my notes.  It was 1.68")  BUT, I look up a yoke for a 66 Cadillac and once source, Speedway Motors, says 1.88" 

[scotth3886]

Ha Ha, I must convert from Metric!  Thanks for the pictures.  The 47.95 mm is
the 1.89 in I mentioned, the 43.2 mm is the smaller 1.70 in, a little more
accurate than my 1.69 in memory. 

Both of these are not 1.58 in, just where does that come from?

In every case the size of the splines on the output shaft is the same.  I do not
know what choices Cadillac made in 1966, but either diameter yoke has been
used in either short or long tail extension housings.  For either length, it is
possible to change to the other dia yoke by changing the extension housing
with its different dia seal and bushing, without removing the trans from the car. 

There were 4 in, 9 in, and 13 in tail extension housings, but that is not the
problem here.  It is necessary to completely dis assemble the trans to change
the shaft to a different length. 

There is also the difference of yokes that just slide over the splines, and yokes
which have a long unsplined outer tube that extends farther in, to seal on an O
ring on the output shaft.  These yokes have a center air vent.  If used on a
shaft without the O ring, oil will come out the vent.  The short yoke has no vent,
and will work with either style shaft.  Bruce Roe

We measured the OD of the yoke when we had the driveshaft out for rebalance and replacement of the front cardan joint and centering kit.  (couldn't find another kit to also do the rear)

Mechanic, Jeremey read it to me and I entered in my phone on the spot.  He also wrote it done and it said 1.58 (edit, I was mistaken.  My notes said 1.68") so same as my note. 

I have the 13" tail extension.

[scotth3886]

Hello Scott,

When I rebuilt my '67 TH400, it had two bushings in the extension housing.  The rebuild kit I got from Fatsco had one bushing, so I ordered a second.  The attached photos show the new bushings (wider/longer) along side the old, original bushings, as well as the fit of the new bushings on the driveshaft yoke.

If your measurements are correct, .100" difference is way too much clearance between the OD of the yoke and ID of the bushing.  The bushing(s) will "crush" a little upon installation, but no where near .100".

In my case, the bushings fit fine over the yoke before installation, with a few thousandths clearance (approx .004").  When the bushings were installed in the extension housing, the yoke would barely rotate, so I honed the ID of the bushings until I was satisfied with the fit.

As Bruce Roe and Roger mentioned, .100" is too much clearance, and is likely to lead to premature failure of the seal.  Transmission bushings should have less than .010" clearance as they function to hold rotating shafts in alignment.  As Bruce Reynolds mentioned, Cadillacs had a unique extension housing in their Hydra-Matics for many years.  Is it possible your car is not fully original?

Respectfully submitted,

Christopher Winter

I've spoken to Don every time I've called Fatsco.  Seems like he is the one who always answers.

He sent me two of the same bushing.   

"Transmission bushings should have less than .010" clearance" 

I agree. 

We haven't taken the tailshaft off yet so I don't know what's in there.  I try hard to have everything I need (or more) so I don't tie their lift up while waiting for parts.  They are, after all, a new car Chevy dealer and they're doing me a big favor to work on this for me.  I can't do much at home because of the HOA.  I don't want to end up losing my house over this car.

[scotth3886]

Egg. On. My. Face. 

I just looked at my original notes again.  It's 1.68" OD for the yoke, not 1.58"

Again, thanks everyone for the help. 

[2manycars]

I just replaced the bushings, clutches, and seals in my 64's TH400 a few months back. Mine took the 5105-L tailshaft bushing from Fatsco. The original was worn to the point that I could rattle the driveshaft inside of that bushing. This was just holding the tailshaft extension over the driveshaft yoke, and no oil seal installed. With the new bushing, you couldn't feel play at all, but rotation in the bushing was nice and smooth. My seal was so bad that if you jacked up the front of the car, trans fluid would just pour out the back. The ultimate cause was that the driveshaft bearing was shot. Car has not been run yet - it is still apart.

Be aware that GM staked that bushing in. You will see the ID dimpled in in two opposing locations. It's a little bit of a pain to get out, but it'll go.

[scotth3886]

I just replaced the bushings, clutches, and seals in my 64's TH400 a few months back. Mine took the 5105-L tailshaft bushing from Fatsco. The original was worn to the point that I could rattle the driveshaft inside of that bushing. This was just holding the tailshaft extension over the driveshaft yoke, and no oil seal installed. With the new bushing, you couldn't feel play at all, but rotation in the bushing was nice and smooth. My seal was so bad that if you jacked up the front of the car, trans fluid would just pour out the back. The ultimate cause was that the driveshaft bearing was shot. Car has not been run yet - it is still apart.

Be aware that GM staked that bushing in. You will see the ID dimpled in in two opposing locations. It's a little bit of a pain to get out, but it'll go.

IIRC, a 64 is an x-frame with a center carrier bushing, for a two piece driveshaft, correct?  So this might not be relevant at all, but what symptoms did you have driving it?   Any harmonic vibration or noise?

[2manycars]

IIRC, a 64 is an x-frame with a center carrier bushing, for a two piece driveshaft, correct?  So this might not be relevant at all, but what symptoms did you have driving it?   Any harmonic vibration or noise?

Yes, it is an X frame with 2 pc drive shaft and support bearing. I have not driven the car much, and not in a couple of years since it has been apart. I do remember hearing bumping noises sometimes (possibly this problem), and the car had less power than expected (worn out engine), and had a massive oil leak. Actually several leaks. One of the worst leaks was from the transmission extension housing. The bad support bearing and worn out bushing caused such a massive leak that the transmission mount was also destroyed.

I went through the trans myself, and had a machinist rebuild the engine. I had also stripped out the climate control and had the mechanical parts rebuilt. Pretty soon, I'll find out how it all turns out.

[scotth3886]

I just replaced the bushings, clutches, and seals in my 64's TH400 a few months back. Mine took the 5105-L tailshaft bushing from Fatsco. The original was worn to the point that I could rattle the driveshaft inside of that bushing. This was just holding the tailshaft extension over the driveshaft yoke, and no oil seal installed. With the new bushing, you couldn't feel play at all, but rotation in the bushing was nice and smooth. My seal was so bad that if you jacked up the front of the car, trans fluid would just pour out the back. The ultimate cause was that the driveshaft bearing was shot. Car has not been run yet - it is still apart.

Be aware that GM staked that bushing in. You will see the ID dimpled in in two opposing locations. It's a little bit of a pain to get out, but it'll go.

The bushing Fatso sent me are 4014s.  I have the long tailshaft TH400 with the 13" tailshaft.  Bushings they sent me are about an 1.25" wide.  Do you recall if you have the long 13" tailshaft and if so, appx how wide were your bushings?