4 speed gurus needed. Output shaft questions.

[kcmash]

OK. I think I am close on this but need some help.

My car has exhibited a vibration when driving 40 and above since restoration.  351 4speed.

Today I slid under the car to check u-joints and found this.  When shaking the front of the driveshaft up and down at the transmission yolk, I get about 1/8 inch of play.  This is with everything assembled.  I feel this could be the source of the vibration.

I did rebuild the transmission during restoration, but am unsure if I did the output shaft bearing.  What do you think I need to test/replace to tighten this up?

Is there another yolk bushing or something that goes in front of the output shaft seal that should support the yolk better?

How tight should this all be?  Should I just remove the tail housing and inspect that, or pull the whole tranny?

Thanks for your help!

kcmash

 

[Hemikiller]

What's the history, or what's been done to the driveshaft & rear axle?

The output shaft bushing can certainly cause a vibration if it's badly worn. I'd think you would remember if you had replaced the bushing, as it's not something that's easy to remove unless you have the correct size driver. 

IMO, mark the orientation and remove the driveshaft, check the u-joints for smoothness of movement, proper seating of the clips, etc. Also check the yoke for wear in the bushing area. If it's good, reinstall it 180° from it's original orientation on the rear axle yoke and road test. 

You remove just the tailhousing to do the bushing, but at that point it's probably easier to pull the whole unit. 

 

[Carolina_Mountain_Mustangs]

There is a sleeve bushing in the tail shaft just in front of the rear seal. You can remove the tail shaft without taking whole transmission out but will lose the grease. You might pull the drive shaft and see if it is even in there. If there is a bushing give Dan Williams a call to find out what the diameter of the yoke should be on the driveshaft. Might be wrong yoke. The clearance between the sleeve bearing and the yoke should just be a few thousandths of an inch. 
Here is link to Dan's web site. I do warn you he will talk your ear off, lol. Great guy will always share and he has any parts you might need. https://www.toploadertransmissions.com/

 

[kcmash]

What's the history, or what's been done to the driveshaft & rear axle?

The output shaft bushing can certainly cause a vibration if it's badly worn. I'd think you would remember if you had replaced the bushing, as it's not something that's easy to remove unless you have the correct size driver. 

IMO, mark the orientation and remove the driveshaft, check the u-joints for smoothness of movement, proper seating of the clips, etc. Also check the yoke for wear in the bushing area. If it's good, reinstall it 180° from it's original orientation on the rear axle yoke and road test. 

You remove just the tailhousing to do the bushing, but at that point it's probably easier to pull the whole unit. 

History is strange.

Lots of parts collected.

Rear pumpkin is a 3:25 posi that I had rebuilt.  
Driveshaft was purchased as a 4 speed driveshaft.  I am unsure.  New u joints on both ends.

No I did not replace the tail shaft bushing.

Why is removing the whole tranny easier.  Disconnect the driveshaft, crossmember, speedo cable, shifter.  4 bolts to remove the tail shaft.  4 bolts to remove the tranny.  Tail shaft is light, transmission is heavy.

thanks

kcmash

 

[kcmash]

Went for an awesome drive tonight and am having second thoughts.

So the problem is the vibration is inconsistent.  It seemed to get worse when the car warmed up then better.  Not sure if  I have something dragging in the brakes up front.  But that stuff is all new, so that makes no sense.

I am definitely puzzled.

kcmash

 

[Carolina_Mountain_Mustangs]

You stated that it had lots of slop so either wrong yoke or bushing missing or worn out. You do not have to pull transmission You will have to support with a jack so you can get the cross member out. Parts house should have tools to get it out if you do not. 

 

[Tnfastbk]

Do you feel the vibration in the steering wheel or in the seat? Is it under acceleration or coasting or both?

Seat is usually drive line

Steering wheel is usually Tires/wheels

Start with the easy stuff. Tire balancing, drive shaft balancing. I had a small vibration once after having the drive shaft out. I took it loose at the rear end and rotated it 180 and helped a lot.

 

[Hemikiller]

Why is removing the whole tranny easier.  Disconnect the driveshaft, crossmember, speedo cable, shifter.  4 bolts to remove the tail shaft.  4 bolts to remove the tranny.  Tail shaft is light, transmission is heavy.

thanks

kcmash

It's the difference of four bolts and working under the car with the stink of gear oil. Your call, but I'd yank the tranny. 

 

[mjlan]

If you know the yoke is loose in the output shaft bushing I'd replace them both before speculating on what other things it could be...

 

[kcmash]

So today I decided to take a look and try some of the advice.

First I rotated the driveshaft 180 degrees and reattached to the differential.  That went smooth, so I decided to check the torque on the differential ubolts.  They were way loose.  So I torqued all of them to 65 ft lbs. Took a drive and the bumps felt a lot better, but the vibration is still there.

The vibration is definitely in the steering wheel and feels like it comes through the seat too.

Looks like winter weather arrives this week, so probably no more test drives this year.  Not sure how to test this anymore.

kcmash

 

[Don C]

I would check the driveshaft for any dings and missing balance weights. You should be able to see where a missing weight was welded on. Also check the runout on the driveshaft, especially if you see any dings.

 

[kcmash]

After many trials and tribulations I am back to this topic. Drove down the highway today for a cars and coffee. Vibration starts at around 50 mph regardless of the gear i am in. When coming offf the highway I put the clutch down and still had the vibration. This really pointed to the driveshaft.

So I jack the car up and search the driveshaft to find NO balance weight on it at all. I believe every driveshaft is supposed to have a balance weight on it. Right?

Observation 2, the lash or play in the pinion gear. How tight should this lash be? Mine seems to have several degrees betweenness forward and reverse rotation. Does that sound correct for a 3:25 posi gear?

Finally, I want to change my pinion yolk back to the original that came with the car. Is that change straight forward, or is that where we set the gear lash and put a new crush sleeve in?

Kcmash

 

[boilermaster]

KC,
I would start by at least replacing the output shaft bushing and seal.
With the new bushing in hand, you can see how well it fits your slip shaft.
As for the driveshaft you have 2 options, get it balanced or clean up the shaft and possibly see where the weight was tacked on (don't use the lost skin method) if you find the tack spot you could use the old worm gear clamp (s) method and see what effect it has on balance, if that does good now you have an idea of how much weight you might need to tack on a weight.
I would save the rear yoke till last, lots of options there too, I prefer to use spacers rather than a crush sleeve, however you would be better off removing the pinion to get it properly preloaded.
if you replace the rear yoke, you can only achieve proper preload, that will not change backlash.
Go one step at a time and test after each step.
Boilermaster

 

[kcmash]

A fellow Ford friend here gave me the name of a reputable gear and axel house close by. They rebuild gear sets, balance driveshafts, etc. I think it is worth it to give them a try.

Kcmash

 

[mjlan]

Was the tail shaft housing bushing ever changed???

If not, do that otherwise you are chasing your tail.

Th driveshaft may or may not need a weight to be balanced. It could be checked for balance while you are changing the bushing.

If you are changing the pinion yoke you should check the the pinion bearing drag when you are finished to make sure you have kept them preloaded during the change. This requires the axles to be removed. The pinion nut is torqued to 250 ft. lb, so it is a major pain the *** to do with the car on the ground, or even on a lift. Easiest to drop the center section out if you are messing with the yoke...

My $0.02 is change the trans output shaft bushing and you'll solve the problem. If you can move the slip yoke up/ down/ sideways in the trans at all then it'll vibrate. What does the outside of the yoke look like? If the area that rides in the bushing is worn at all you should replace that too...

 

[kcmash]

I have not replaced the tail shaft bushing yet. They did add a weight to the driveshaft and is much better, but the rear view mirror has a constant vibration while driving. So maybe there is still something, or maybe not.

Kcmash

 

[kcmash]

Well, I am still getting vibration, but it starts more around 70MPH now. I will look into the output shaft bushing next.

Yes the driveshaft was out of balance, but I still have more.

Kcmash