MTFCA Forum

Hello,
Broke out the t for the first time and noticed a flow of grease and oil out of the u joint. It was grease followed shortly after by a mix of oil. I believe the grease melted and flowed out. What grease should be used in the u joint?
Regards,
Matthew

You should have one gasket. Between the 4th main and the transmission. The cover on the outside of the U joint should be tight against the 4th main. The grease should be pumped until full and the bushing in the driveshaft also be packed with grease. Thick grease. The grease will keep some of the oil from flowing out or down the tube to the rear axle. If that doesn't fix it, you might need to do more work. Such as replacing the 4th main with new babbitt, and be sure there is a plug inside the rear driven shaft between the clutch and the U joint.
Norm

M.Sinclair wrote: ↑

Tue Mar 28, 2023 9:31 pm

Hello,
Broke out the t for the first time and noticed a flow of grease and oil out of the u joint. It was grease followed shortly after by a mix of oil. I believe the grease melted and flowed out. What grease should be used in the u joint?
Regards,
Matthew

Everybody will have their preference of course, but for me it's "Red 'n Tacky"...in I get it in a tub to TOTALLY pack the U joint housing when the engine's out, then I cheat and have the large grease cup with the zerck in it that you get from Langs for adding more grease every oil change. I pump about 20-25 pumps when I do. Sounds like a lot, but if you "test pump" on the bench on a paper towel, you will see not much comes out each time you pump the gun handle.

" a flow of grease and oil out of the u joint. It was grease followed shortly after by a mix of oil"

You may have engine oil in the grease, oil that's leaking past the 4th main. Something else to check. jb

Ditto on the Red & Tacky and grease zerks.
Craig.

If enough parts are worn from the fourth main back engine oil can make its way all the way into the differential. Check the level there to see if it is too high.

The add on transmission screen adds to the problem, dumping extra oil on the 4th main.
A partial patch to slow the oil is to turn the 4th main 180 degrees, putting the oil hole down.

I have determined that the "earlier" accessory screens had larger holes & didn't hold back as much oil.

John, If the oil hole is on the bottom, will it allow a lot more oil to flow through the 4th main going up hills? I understand from a discussion with Gene French that many 4th mains have no hole.

Overfilling the crankcase could result in more oil reaching the ujoint area and diluting the grease.

A long, hard uphill run might do the same.

If your rear axle isn't gaining fluid, I'd check the oil level and pump the ujoint and driveshaft bearing full of red tacky grease and see what happens.

Keep a check on the rear axle lube level to avoid greasing your brakes if it gets too high.

Any new and unusual mechanical sounds would call for further investigation.

noelchico wrote: ↑

Wed Mar 29, 2023 2:07 pm

John, If the oil hole is on the bottom, will it allow a lot more oil to flow through the 4th main going up hills? I understand from a discussion with Gene French that many 4th mains have no hole.

Possibly a little bit more. Not a lot more since oil still enters around the mains open end. Also the spinning spring retainer cup shields the end some.
But how steep & constant are the hills you drive?
A correctly fitted 4th main has .0015-.002 clearance. That doesnt allow a lot of oil to pass thru.
I would want the oil hole in play until I detected the oil diluting the grease with a fresh, tight bearing.
The problem of diluting the U-joint grease comes from a much more worn bearing and/or the absence of the plug in the output shaft.