Leaky Transmission Questions

M274 Mechanical Mule Knowledge Base
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Leaky Transmission Questions

Post by Speedracer » Sat Mar 30, 2019 9:04 pm

Due to some issues I decided to pull the engine from my M274A5, found that the clutch disc is soaked in gear oil, and a significant amount of gear oil was in the bellhousing. I removed the outer bearing retainer from input shaft, will need to replace the seal in there. I realize I will also need to replace the shift shaft seals. Can the front transmission seal be replaced without removing the transmission? Any other seals that I should replace since I'm in there?

Before I pulled the engine the transmission seemed to shift fine, just when it was started up and I pushed in the clutch pedal it would grind going into first or reverse gear, once moving it didn't do it again and the other gears shifted just fine. I believe the clutch disc soaked in gear oil was the cause of this problem.

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Re: Leaky Transmission Questions

Post by muleman7 » Sun Mar 31, 2019 7:22 pm

I seldom find the seals on the input safe as the culprit for gear lube in the bell housing. I would first check the LR axle seal area on the right inside of the bell housing and see if it shows any leakage. If it does you will need to pull the LR gear cover to withdraw the axle. Then you will need to remove the RR drop gear housing assy and ring gear to install the new axle seal. Drain the trans gear lube.

All transmissions other than the M274 or [M274-A3 if original] use 2ea input shaft seals. The M274 and A3 use 1ea seal.

I remove 7ea of the 8ea 7/16 frame tube bolts and this allows the trans to remain attached to the mule but drop sufficiently to remove the drop gear housing as the mounting flag will not clear the frame tube and rear bed support tube.

Leave loose the bottom left frame tube bolt on the left rear frame tube. You do not need to remove the RR bed support tube. If you want it removed it is attached to the bed via 2ea 3/8 bolts.

Replacing the front output trans shaft seal.

1-It is less messy to drain the trans but not absolutely required just have a catch bucket handy.
2-Remove the drive shaft.
3-Drill a hole in the seal casing use a dent puller with a screw or tapered screw the hammer out the seal.
4-If that does not work remove the bearing retainer[outer housing] and drive out the seal.
5-Check the yoke seal surface for rust or pitting and sand as necessary to obtain the beast sealing surface.
5-Use gasket sealer on the assembly surface to prevent leaks. I like Permatex Aviation Form-A-Gasket. Make sure to keep the drain hole open on the bottom of the shim pack.

2nd and 3rd are the only synchronized gears you must come to a full stop to shift into 1st or rev. The soaked clutch disk could have caused the initial clash into 1st or rev. I generally start off in 2nd high to avoid constant upshifting from 1st.
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Re: Leaky Transmission Questions

Post by Chuck W. » Mon Apr 01, 2019 11:22 am

As Charles says, it's most likely an axle seal leaking transmission oil(right side) or drop axle oil (left side) into the bell housing.
It could be either side, or both, but If it's the right side, as he says, you will have to remove the differential bevel gear, as the seal goes in from the other side.
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Re: Leaky Transmission Questions

Post by Guam0311 » Tue Apr 02, 2019 11:16 pm

You have came to the right board for help. Of coarse the manuals and the illustrated parts reference is a must have, however the tried and true real world methods it doesn't show. the small things that you will need at some point. tooling, parts, references, etc. Their are Board member here that are very knowledgeable and have helped me out. two that come to memory are Muleman7 and Chuck. Most people on here are friendly and helpful as well.

I replaced the seals you are talking about. I took lot pictures and posted many subjects on this site. "technical section". I am still in the full rebuild process. If it helps you check the photos out. A picture can be worth a million.

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