MTFCA Forum

I drained and refilled my differential earlier this spring. I’m now driving it quite a bit more (at least until some serious missing developed last weekend, more on that later). I was pretty careful not to overfill but may not have taken into account the warmer temperatures. When I came out to start sorting out the rough running, I noted that there is differential fluid leaking. Is this a sign of something more serious or just that the fluid heated up in the warmer temperature and I will need to drain some off? I have not gone through the rear end yet and was hoping to hold off on that until next winter.

Seals are leaking and/or oil is traveling from the engine into the differential and going out at the hubs. Either way, seals are leaking.

IMHO differential oil leaking out at the wheels can mean only one thing - failed seals. Each side has 3 seals, the outboard grease seal, the inboard grease seal and the inner differential oil seal. They probably will only get worse as time goes by and you accumulate miles.

The only fix that I'm aware of is to remove the rear end, disassemble it, replace the seals, and reassemble it. You can replace the 2 grease seals without disassembling the whole thing, but the oil is getting past the oil seal. The only way to replace that seal is to take it apart.

It's not a big money job as far as parts go, but it's a lot of work. The good news is that, unlike a regular T differential, the TT worm drive has no adjustments. It just bolts together, simple. You'll just need a medium size gorilla to pull it apart. Also note, there's another felt at the drive shaft that you'll want to replace.

If you do take it apart, it's a good time (the only time) to check everything else. I don't know how long yours has been leaking, but when I took mine apart it had obviously been leaking for a very long time. The oil washes the grease out and that allows excessive wear on the roller bearing, the sleeve, and the axle. It needs to be fixed.

Thanks for the responses, even though it’s not what I wanted to hear. I guess my son and I have another project this summer.

-Bruce-
Don't know whether you know..... The TT Ruckstell is supposed to use a 600 weight gear lube. Lang's does carry it. The 90 weight we find in the stores is no where near the necessary viscosity. Not saying you won't need to replace those seals, but I prefer to being a bit lazy and trying to take the easiest and most plausible answer, if possible. Imagine 5 weight oil vs. 50 weight oil in a racing engine. Are those seals made of felt? Imagine filling a jar with water, and another jar with fresh concrete. Then, use a sieve as a cover, and do the upside down thing.... You get the idea. Did you fill the differential with the 90 weight???? Sometimes, the simplest solution can be the easiest and best solution. But, by no means, am I an expert.... However, the Dyke's Manual agrees with my viscosity thought. Good luck!

The only fix that I'm aware of is to remove the rear end, disassemble it, replace the seals, and reassemble it. You can replace the 2 grease seals without disassembling the whole thing, but the oil is getting past the oil seal. The only way to replace that seal is to take it apart.

This is the case.

You may find that even after the replacement that oil still weeps out due to wear on the axles. They only have to be a little but out of round and/or undersized. In any case reducing that leak is important.

I use 140W oil in my Ruckstell TT rear. MAKE SURE IT IS "NON-EP" additive oil. The EP additive corrodes the bronze gear and that can get very expensive fast!!

All the best - and make sure you get the latest version of the MTFA Ruckstell rebuild manual. That helps a lot in the process (there is a section on the TT at the end of the manual).

All the best,

Adrian

Home made carrier for modern oil seals - there is enough clearance if you measure carefully

Another good reason to strip it down is you never know what sludge you may find that built up in there, so a nice clean out in itself is a good idea (friends TT diff:)