[chiphead]

How loose does the TH400 extension housing bushing/yoke fitment have to get to cause driveline vibration? What is the clearance between the yoke and the bushing supposed to be?

I've had a driveline vibration at 65-75 MPH with both the original driveshaft and the aftermarket shaft that's in there now. The yoke has a a few thousandths of slop if I wiggle it up and down in the extension housing. I replaced the seal when I swapped driveshafts, but can't remember if I did the bushing.

I pulled the shaft last night in order to drop the trans. The new 1350 yoke has the coating worn off on one side, after 2K miles. It's def been wobbling as it ran. Can I just pound in a new bushing or what else do I need to check?
With yoke removed, I can wiggle trans output shaft roughly .040" back and forth. Is that normal?

[65 Lamnas]

Originally Posted by chiphead

How loose does the TH400 extension housing bushing/yoke fitment have to get to cause driveline vibration? What is the clearance between the yoke and the bushing supposed to be?

I've had a driveline vibration at 65-75 MPH with both the original driveshaft and the aftermarket shaft that's in there now. The yoke has a a few thousandths of slop if I wiggle it up and down in the extension housing. I replaced the seal when I swapped driveshafts, but can't remember if I did the bushing.

I pulled the shaft last night in order to drop the trans. The new 1350 yoke has the coating worn off on one side, after 2K miles. It's def been wobbling as it ran. Can I just pound in a new bushing or what else do I need to check?
With yoke removed, I can wiggle trans output shaft roughly .040" back and forth. Is that normal?

I don’t know how much clearance or wear it takes to cause a vibration. The wear limit on that bushing is .008”

Measure the OD of the yoke with a mic, and the ID of the old bushing too. Put in a new bushing and remeasure.

[694.1]

My low mileage '57 vibrated around 35-45. almost undetectable slop in the yoke but I measured things up and it seemed not much more a .003 wear.
Slid a new bushing in and I was somewhat amazed. Problem gone. May well try it, there are not many cheaper fixes

[Half-Inch Stud]

Have you considered Vibration with no wear?

The bushing is transferring the drivrshaft vibration to the tail/crossmember.

[chiphead]

With 2 different driveshafts? The underside of the car had oil slung all over it from the yoke seal leaking. So I replaced the seal and replaced the driveshaft thinking that would fix it. It fixed the leak but not the vibration.

I didn't drive it much with the original BOP 10 bolt, so I can't say for sure if it vibrated with that rear end. It was wasted so I swapped to a Ford 9" from my old race car. Its possible the pinion angle is now off. The 1330 yoke on the Ford 9" will accept a 3R Ujoint, so I used the factory driveshaft for awhile until I could get my aftermarket shaft cut down 1" to fit the TH400. My other car had a TH350.

Anybody got a good method to verifying pinion angle? I've got the upper arms adjusted to stock length, but I just realized the upper ears on the Moser housing may not be in the exact same place as the BOP housing....

[mgarblik]

I would go ahead and replace the bushing just because of what you have described. Pretty easy. While the tail housing is off, really inspect the transmission mount. Driveshaft angle can cause vibration at certain speeds due to incorrect angles the u-joints can't handle. Possibly the mount has sagged over the years.

[Half-Inch Stud]

@chiphead, hmmmm seems to me the Center Support bushing may be clapped-out and allowing the FWD+DIR Packs to orbit the centerline rather than spin on axis.

That would give a big vibe from a "normal" bushing wearout pattern. But i 's expect the Trans to lose the shift quality when the C-Support bushing wears that badly.

When the Center-Support bushing is worn, the DIR-Pack apply can stake the offset and be orbiting the Clutch Packs for big vibe on 1-shift, then re-apply more-or-less aligned on another shift.

[steve25]

You would recall taking the tail shaft off to replace the bushing I would think.

I would bite the bullet and replace the bushing .

Even just .004” of rock in the center of the yoke splines gets multiplied at the main OD of the driveshaft..

[HWYSTR455]

I agree with replacing the bushing too. If the bushing is worn, it can cause the seal to wear faster, so if it starts leaking again you'll know what to do.

I'm sure you have, but will ask anyway, both driveshafts you tried were balanced? 'Typical' balance job from most shops only balance up to like 60mph, so if the vibration persists, you may want to try a diff shop to have the shaft balanced.

I've been using the Tremec 'Toolbox' phone app for setting angles, it works well enough for me. You do have to take your time measuring, and 2x / 3x check it.

Laser levelers work good too, using a U-joint cap as a centerline. A digital angle finder will give you the readings you need. Then just do the math.

There are calculators online where you can plug the measurements in if you don't want to do the math manually. But read the calculator's fine print so you know what the variances are. The ones for rock crawlers and tractors are not appropriate.


.

[steve25]

I terms of tweaking the balance if need be watch some of the videos on using a cooling system hose clamp get the high speed balance better.

It can be time consuming but rewarding.

[Bill Eveland]

Typically 65-70 is more of a wheel vibration i would think. The vibration rpm can be measured and determine if its wheel speed or driveline speed. Are we talking stock install and driveshaft angle in order? Typically a wheel speed is 14-16 ish hertz for whats called a first order tire vibration, which is one fault per revolution. So would multiply that by the ring and pinion to get a much higher number , but usually mph isnt that high.

There are other factors as well, if the backlash variation on the ring and pinion is too high. I think the play you mentioned doesn't really sound like a big issue.

As far as messing around with adding hose clamps to try and change the vibration, it does help to add some weight to change the rpm that something can vibrate at, outside of just trying to fix an out of round spot. .

[VCho455]

Here is a link to the Spicer driveline angle calculator. On the same page is a video on how to measure the angles.

https://spicerparts.com/calculators/...gle-calculator

If you're patient you can get good repeatable measurements with a common analog angle finder.

[chiphead]

In the middle of the bushing job now. the bushing I just drove out is 1" long. The replacement bushing is 1.5" long. I drove it into the housing, and it's about 1/8" longer than the housing bore. I've installed it so that the excess is towards the front (transmission case side). Is this good to go? I have not installed the new seal in case I need to move it around or stake it or something.

[mgarblik]

Install sounds correct. Bushing should be flush with the counterbore for the seal. Bushing should be a light press fit. If it just slipped into position or had to just barely tap in, the housing is worn. You can remove the bushing and reinstall with locktite green. ( sleeve install compound). Should not need to stake the bushing or the seal.

[chiphead]

I drove it in with a bushing driver and a ball pein. Clearance to yoke is about .006. I installed the seal and put it back on the trans.

[chiphead]

Next step is confirming driveline angles. The issue is the car sits low and I can't really fit under it. If I put all 4 tires on equal height wood cribs, would the ride height be close enough to measure the U-joint angles?

[HWYSTR455]

Yes, that will work.

.

[67Fbird]

It doesn't matter if the front end is 3' higher than the rearend!!!! as it is all about equal and OPPOSITE angles. measure the YOKE angle then the driveshaft angle then the rear-end yoke angle ADD-SUbtract.... should be within 2-3*

[chiphead]

Got one of those Klein digital angle finders. Man that thing is nice.

With the front end on stands higher than the rear, the front U-joint angle was 3.5 down. Once I got the 4 tires sitting on the blocks at ride height, the front angle was 2.6 degrees down. Rear pinion angle didn't change much, so yeah, weight on the tires matters.

The important thing is the rear end isn't 2.6 degrees up like it should be, it was 2 degrees down. Welp, there's the problem.... I think the issue is threefold:

1: Upper ears on ford 9" rear in different location than stock BOP
2: Ford 9" has low pinion vs BOP
3: Car is lowered vs my other car. Apparently on a 4-link that pivots the yoke downward as the car sinks.

I was wondering why the upper arms were set longer than stock when I removed the rear from my donor car. I set them back to stock for a '67, I've now re-learned that's not right. Tonight I cranked the upper arms about 4 turns out, the pinion angle is now about 2.9 degrees up. Driveshaft is about 0.8 degrees down now. It's late, I'll finish up another day. Will likely set pinion to 2.4 degrees up and see how she rides.