400ISL engine front seal leaking/front seal on transmission leaking

[Bob R]

1) The front seal on my 400 ISL engine is leaking.  It drips oil very slowly.  My RV sat in the garage over the winter months and there was a small spot on the floor beneath the front of the engine.

How serious is this leaking to the long term "health" of the engine?  Should I have it replaced or leave it till the leak is worse?

2) The front seal on the Allision 3000 transmission is leaking as well.  It is also a small leak.  The is a small area on the floor beneath it that the fluid has leaked.  Can I continue to operate the RV without replacing these seals?

Any advice from you guys would be appreciated.

Bob Raffety

2005 Dynasty Countess lll

[jacwjames]

Did both seals start leaking at the same time??

[DavidL]

There isn't any issue with driving it

Just ensure you monitor the leak rate, and most importantly, that both the engine and trans has the proper amount of fluid.

If it's just a dab of oil, I wouldn't touch it.

decent odds it will "reseal itself" once the engine / trans is heated up and ran for a few minutes.

[Bob R]

I think the transmission leak is bad enough that the fluid is being blown onto the bottom of the undercarriage.  I drove it about 50 miles and it looks like the leak is worse when it is in service.  The drip spot on the floor was very small.  But that may have been because the transmission had not been operated for several months while the RV was in the garage during the winter.

Thanks for the reply, David.

Bob

Jim J

The leak on the front of the engine has been around for about one year.

The leak on the transmission was just noticed this year when I took the RV out of storage and drove it a short distance (50 miles).

[dl_racing427]

On 5/12/2023 at 10:22 AM, Bob R said:

I think the transmission leak is bad enough that the fluid is being blown onto the bottom of the undercarriage.  I drove it about 50 miles and it looks like the leak is worse when it is in service.  The drip spot on the floor was very small.  But that may have been because the transmission had not been operated for several months while the RV was in the garage during the winter.

Thanks for the reply, David.

Bob

Jim J

The leak on the front of the engine has been around for about one year.

The leak on the transmission was just noticed this year when I took the RV out of storage and drove it a short distance (50 miles).

The front seal leak on the engine is the easier to fix, though if it's only a drip or two when parked, I don't know as I'd worry about it.

It sounds like your tranny leak is worse.  That one would require pulling the tranny to fix, which you may want to leave to a shop.
I don't know what the Allison tranny weighs, but I'm sure it's significant.  Without the proper equipment to handle it, it could be a somewhat dangerous job.

You may want to wait until you drive it a couple more times to see if it improves, but I agree, if fluid is being sprayed on the undercarriage, it's big enough to be a concern.  Definitely keep an eye on the fluid levels.

[Guest Ray Davis]

 

When my hydraulic pump was leaking I bought a package of rags at Walmart and kept one tied around the pump until I got it fixed.   Probably not as easy on a trans leak but might be worth looking at.

Edit,,,, My hydraulic system has red transmission fluid in it,  could your leak be from there or a hose?

Edited May 14, 2023 by Ray Davis

[Bob R]

I took the RV to a truck service shop.  They confirmed that the leak is on the front seal of the transmission.  They have scheduled the fix for next week after they have the parts to do the job.  The shop is an Allison approved workshop.  So maybe the problem will be handled correctly.

I think I will take DavidL's advice and wait and watch the engine seal.  It isn't leaking a great amount.

Thanks for the advice.  I appreciate you guys with all the experience.  This is a great website for us "not so informed" RV owners.

 

Bob R

[AndyinMelbourne]

I just replaced the output shaft seal on the transmission on mine (400 ISL with MH3000 Transmission).  It took about fifteen minutes.  Got the seal from Cummins ($56) in Orlando.  One of my U-joints failed so I already had it all apart.  That is another story that I'll write and post later.  The seal wasn't leaking much but I prefer to replace before it gets worse and since I already had the driveshaft off it wasn't much additional work.  I used a PVC fitting in the correct diameter to tap the new seal back it.  I think it is a 4" diameter.  Worked well.

[jacwjames]

2 hours ago, AndyinMelbourne said:

I just replaced the output shaft seal on the transmission on mine (400 ISL with MH3000 Transmission).  It took about fifteen minutes.  Got the seal from Cummins ($56) in Orlando.  One of my U-joints failed so I already had it all apart.  That is another story that I'll write and post later.  The seal wasn't leaking much but I prefer to replace before it gets worse and since I already had the driveshaft off it wasn't much additional work.  I used a PVC fitting in the correct diameter to tap the new seal back it.  I think it is a 4" diameter.  Worked well.

I believe OP has a front seal leaking, the transmission has to be pulled to replace.

My question on timing of both leaks has to do with cause of failure, excessive vibration could cause a seal to leak.  Just something to look at.