A833 23-spline tranny and drivetrain vibration - culprit found, need help

[Cornpatch MO]

Thanks. Yep, thought about that too. Nothing like that is visible to my old nekked eye, but that doesn't mean it's not there. We'll definitely check that out closely when we get it all apart to do the bushing.
I'm pretty sure my driveshaft is ok (given previous engine/trans setups not having this issue) and yes, I'm going to get the bushing rectified pronto so that it doesn't become an issue.

No one ( except me ) has mentioned that your yoke movement could be from the splines themselves , being worn. You can't see the end of the yoke tube, so it is hard to tell. This happened a lot on large 10 wheeler trucks. .......................MO

 

[moparedtn]

No one ( except me ) has mentioned that your yoke movement could be from the splines themselves , being worn. You can't see the end of the yoke tube, so it is hard to tell. This happened a lot on large 10 wheeler trucks. .......................MO

Oh man, I hope not!

 

[Cornpatch MO]

Oh man, I hope not!

If those splines are worn, it will be on the yoke side. The yoke is softer metal than the trans. output shaft. .............................MO

 

[Fran Blacker]

If those splines are worn, it will be on the yoke side. The yoke is softer metal than the trans. output shaft. .............................MO

Bet you Ed will be happier with that, but hope it's curried with bushing. Couldn't tell by having car in gear with rear wheels up and turn yoke CCW then CW then repeat?

 

[oldbee]

Hate to stir things up but it occurs to me that diff pinion angle could be off also. Had to throw that out there!

 

[moparedtn]

If those splines are worn, it will be on the yoke side. The yoke is softer metal than the trans. output shaft. .............................MO

Thankful for that!

Bet you Ed will be happier with that, but hope it's curried with bushing. Couldn't tell by having car in gear with rear wheels up and turn yoke CCW then CW then repeat?

That's what I had and I just felt slop all the way around. Hoping it's outside the yoke (bushing) and not inside (splines).

 

[moparedtn]

Hate to stir things up but it occurs to me that diff pinion angle could be off also. Had to throw that out there!

Always thankful when you jump in here, sir.
Thought of that, but nothing has changed there and this is a problem new to this combination - didn't happen before.

 

[oldbee]

LOL- never say never!!! That said I never checked my angle once in 49yrs.

 

[Fran Blacker]

Always thankful when you jump in here, sir.
Thought of that, but nothing has changed there and this is a problem new to this combination - didn't happen before.

Oldbee stir things up.....

 

[oldbee]

Fran you know the crazy things that just pop into your head after reading posts. I would be remiss if I didn't chime in.

 

[oldbee]

Ed I'm with ya, but just thinking I got a frt.end alignment in the spring and tech said he got real close on caster or camber(?) but he thought the frame(?) had probably shifted a bit. Understandable it's 49yrs old even though I have 2x2" tubing with tiring in the frt&rear.

Always thankful when you jump in here, sir.
Thought of that, but nothing has changed there and this is a problem new to this combination - didn't happen before.

Im

 

[Bobo]

Greetings y'all.
In the next step of the long-term resurrection of my '68 GTX, I'm on to the next problem now that the basics are all in place and functioning - finally. Thank God.
Car has replacement 440, new clutch (Centerforce) etc. and a replacement "donor" 23-spline.
Driveshaft is stock. Rear end is a fresh rebuilt 8 3/4 with 3.55 and SureGrip.

Anyways, at speeds over 70mph and under load, a fairly heavy vibration occurs and just gets worse with more speed. If I lift, it goes away. If I push in the clutch and/or pull it out of gear at that speed, the vibration goes away. It isn't in the engine or clutch or in wheels.

This is telling me there's a possible problem with the u-joints - or even in the tailshaft housing, so I got under the car and checked things out.
Rear u-joint checked out fine, but I took it loose and reinstalled it 180 just in case I had installed it "clocked wrong" before.

Grabbed the driveshaft yoke at the rear of the tranny and Bingo - there's quite a noticeable amount of slop here. I had replaced the seal on the transmission when I got it, but the actual condition of the transmission was a total unknown before.
It shifts really nice and it's a quiet unit, but this slop at the output is almost definitely the cause of the vibration.
Is there just a bushing that needs replaced in there? Is this something I can do?
Or is there more to it?

 

[moparedtn]

Ed I'm with ya, but just thinking I got a frt.end alignment in the spring and tech said he got real close on caster or camber(?) but he thought the frame(?) had probably shifted a bit. Understandable it's 49yrs old even though I have 2x2" tubing with tiring in the frt&rear.

Im

Yeah, but I didn't have this problem at all with the same driveshaft and rear end, so I'm just trying process of elimination.

 

[moparedtn]

BeeKeeper is kindly coming by this evening (in this ungodly heat!) to get this done, so I reckon we'll know something soon.

 

[oldbee]

Always thankful when you jump in here, sir.
Thought of that, but nothing has changed there and this is a problem new to this combination - didn't happen before.

I was enlisted,, no need for "sir". Lol.

 

[AR67GTX]

I recently got into a mood to rebuild transmissions - doing my A727 over the winter and rebuilding my Corvette's Muncie with a new supercase and M22 gear set this spring. I test fit the yoke on the bare tail shaft of both transmissions at the time (new yokes) and both had some perceivable movement in the splines. But once the transmissions were together and the yoke inserted into the bushing over the splines - neither had any perceivable movement at all. So I wouldn't loose much sleep over spline wear and fit.

On a separate note, I did find that it's somewhat hard to find a proper yoke for a 60s era 727. The first one I got turned out to be rifled for a late model Torqueflite derivative and I found out that sometime (maybe in the 90s) they changed the spline dimensions on the output shaft. A lot of the venders don't seem to be aware of this (ahem Summit Racing). I finally found a correct yoke at Mancini Racing.

 

[moparedtn]

Well, the verdict is in.
A couple verdicts, actually:
1. Beekeeper (Scott) is an awesome dude, a credit to the hobby. It was a pleasure to meet him and he got right to it, doing the brunt of the work under the GTX this evening. I did helper duty.
That tool for the bushings works really well, too. No problems at all.


2. Here's the old bushing:

It was pretty worn, to the point the grooves were almost gone in places.
New one went right in, too.
The yoke does indeed have some wear, to the point of having an almost imperceptible ridge in it right where it rides in the bushing - and since this transmission is new to the driveshaft, I'm sure it's wearing in a slightly different place now, too.
Probably best to fetch a new one one day soon.

Oh, did it help?
Yessir, quite a bit.
We took off for a drive after we got it back together and really, that was only about the third time the car has even been down a highway since I got it all back together.
The car felt really good, very smooth even - even with me still learning that weird-assed Centerforce DualFriction clutch (strange clutch, but I think I like it).
There's still a little vibration over 75 or so but it goes away now with more speed or by letting up; probably the wear in the yoke showing up some.

By George, I think I have an actual car here. VERY happy right now.
Thanks for everything, Scott!
Again, you holler anytime I can help.
Ed

 

[moparedtn]

I was enlisted,, no need for "sir". Lol.

Haha, sorry man, I address anyone I like/respect with sir.
Brought up right - least, they tried to raise me right.

 

[khryslerkid]

Haha, sorry man, I address anyone I like/respect with sir.
Brought up right - least, they tried to raise me right.

Your the only hell your momma ever raised!

When someone calls me sir, I tell them "that was my dad's name".

Nice to hear you're on the road again. You got a grip on her now

 

[66Satellite47]

Don't go too long with that slip yoke or the new bushing will be junk.