Hi all,

I am will be checking the clearance on my 4th Main and tailshaft... What is the minimum/optimum clearance and the maximum clearance before I need to get it rebabbitted??

I have a oil leak around the 4th Main which I am trying to solve.

Any figures re: clearance would be greatly appreciated.

Cheers Simon

Simon
Install one of the roller bearing fourth mains and solve any problems here.

Donald thanks for that....

Trying to stay as original as I can but it is an option..

Cheers Simon

Them there roller bearings have had problems on engines before 26 when the flex broke the c.chafts
till Ford bolted the transmission cover to the block. What year is your motor?

I think?
Jake C.

I hardly know where to start. If you are experiencing an oil leak at the ball, try unbolting the clamp ring, clean it and reinstall it coating the inside surface with silicone sealant.
If you have excessive clearance in the 4th main, say anything above .006-.008", the problem is probably due to tailshaft run out and will not be corrected with a new 4th main with a tighter fit. In short order the babbitt will conform to the movement of the tailshaft.
You really don't want to capture a tailshaft with run out. Let it move as it wants to. If you install a ball bearing 4th main, you force the trans shaft to flex as it turn and risk breaking a crankshaft.
Besides, a tight fitting 4th main won't stop the oil from passing into the ball of the torque tube. Its designed to pass oil. If you have an early car, check to see if there is a plug inside the tailshaft to prevent excessive oil passage. If there is none, buy one from a parts supplier and install it.
Rather than do all that, just seal the ring around the ball with sealant and be done with it.

I believe that the clearance on the 4th main should be .003" - .006".

Dave S.

Simon,

How bad is your oil leak? It is nearly impossible to totally eliminate all oil leaks from the ball joint area.

If I could respectfully add to Richard's point about runout. I agree that runout should be eliminated, or made as little as possible, before assembly for the reasons he notes. However, no matter how good you get the alignment and no matter how carefully the trans is balanced, a loose 4th main will allow the tailshaft to run out and vibrate due to lack of support and imperfect, (nothing is perfect), balance when running down the road. It will also stress the crankshaft.

Kudos to Dave S. who actually answered the question you asked, (unlike me). And, for what it's worth, I agree totally with his advice on clearance.

This applies to oil leaks at the U joint ball. Sometimes a gasket has been installed between the 4th main and the ring that holds the driveshaft to it. There should be no gasket here. If you install one, it will cause the ring to be too far from the ball and oil and grease will leak out.
Norm

Thanks all for the responces...

The post was killing two birds with one stone.

I am rebuilding a spare transmisson and wasn't sure about the clearance on the fourth main...

and on my '23 I have an oil leak - which seems to be coating the torque tube, diff and wheels with splatters of oil... When the transmission was rebuilt a year or so - I checked the soft plug and sealed it in place with gasket goo... so hoping that has shifted....

I have had the hogshead off since then and maybe the gasket has been torn...??? no sure haven't been under yet to clean it all up and see if i can track where the leak is coming from.

I have read comments posted that transmission screens can cause more oil to come out the 4th main??? I have a screen installed and that the remedy for the leak was to rotate the 4th main by 90 degrees????

Can anyone shed any light on the rotating the bearing and if that will cause a lack of oil on the bearing???

Thanks in advance,

Simon

Simon,

Some say that the screen deflects too much oil to the 4th main, while others say it starves the 4th main. Either way, I personally would not rotate the oil hole.