Allison, PTO internal leak "from" transmission

[Windecker]

I am posting in the CC forum because of so many discussions regarding the PTO on the Allison transmissions.

What I have is a Monaco with the 4000 series transmission that I believe is putting transmission fluid from the transmission, through the PTO, and Sauer cooling fan hydraulic pump into my hydraulic reservoir. This is backwards of what I would expect from a leaking seal.

Basic facts, over several thousand miles my hydraulic tank (also filled with transmission fluid) creeps to totally full and my transmission creeps to slightly low.
I have a wet PTO as shown in the picture.

I presume the pressure coming from the hose on the left in the above picture is supplying pressure fluid to both ends of the PTO (the red doodad). I assume where it enters the PTO in the center at the T is supplying pressure to the drive end splines of the pump and is or should be protected by a Garloc seal.
I assume the Pump itself (to the left of the PTO in above picture) is sealing the drive splines "from" the pressure the pump is creating within, again with a Garloc seal.
Garloc seals seal really only in one direction.

So, given the shaft is supposed to be lubed, how do they keep pressure fed transmission fluid from entering the hydraulic pump down the shaft and past the Garloc seal or am I just missing something?

Further, who and the heck do you contact about this? I called Allison and they had zero clue and tole me to take the MH to a dealer for repair.

Other pictures just for reference.
Thanks in advance!
Windecker

[BarneyM]

Originally Posted by Windecker

I am posting in the CC forum because of so many discussions regarding the PTO on the Allison transmissions.

What I have is a Monaco with the 4000 series transmission that I believe is putting transmission fluid from the transmission, through the PTO, and Sauer cooling fan hydraulic pump into my hydraulic reservoir. This is backwards of what I would expect from a leaking seal.

Basic facts, over several thousand miles my hydraulic tank (also filled with transmission fluid) creeps to totally full and my transmission creeps to slightly low.
I have a wet PTO as shown in the picture.
Attachment 220402
I presume the pressure coming from the hose on the left in the above picture is supplying pressure fluid to both ends of the PTO (the red doodad). I assume where it enters the PTO in the center at the T is supplying pressure to the drive end splines of the pump and is or should be protected by a Garloc seal.
I assume the Pump itself (to the left of the PTO in above picture) is sealing the drive splines "from" the pressure the pump is creating within, again with a Garloc seal.
Garloc seals seal really only in one direction.

So, given the shaft is supposed to be lubed, how do they keep pressure fed transmission fluid from entering the hydraulic pump down the shaft and past the Garloc seal or am I just missing something?

Further, who and the heck do you contact about this? I called Allison and they had zero clue and tole me to take the MH to a dealer for repair.

Other pictures just for reference.
Thanks in advance!
Windecker

Windecker,

Two possible problems. When the wet kit is installed a flow reducer is placed inline going to the spline area in the PTO. The drain or return inside the PTO is very small and if the fluid enters too fast it will not be able to return to the trans fast enough and some will be force past the hydraulic pump seal and end up in the hydraulic reservoir.

The other possible reason is the return inside the PTO is partially blocked and causing the same problem.

Has this always been a problem or is it something new? If it's always been a problem you will need to install the flow reducer to fix the problem.

[Windecker]

Thanks Barney. I understand exactly what your saying but have no clue how bad or long the situation existed.
The coach is new to me about 1.5 years now, can't recall how many miles, maybe 13K since. Hydraulic tank has always been a little above full and I left it that way.

I found the tank totally full in May 1000 miles into a 2000 mile trip, drained it off to normal level and have been watching it close since. Transmission has always said normal level till this weekend when it finally showed down 4 quarts. Maybe the float was sort of stuck or something. I drained off about 1.5 more quarts from the hydraulic tank as the level had creeped back up about 1/4 inch on the dipstick since my 2000 mile trip. I think I have put about 4500 miles on it since the May trip/original tank adjustment.

Total fluid transfer has been about 1.5 gallons.

Can you see the reducer from looking at the hydraulic fitting or is it inside the housing?
Thanks
Windecker

[BarneyM]

Originally Posted by Windecker

Thanks Barney. I understand exactly what your saying but have no clue how bad or long the situation existed.
The coach is new to me about 1.5 years now, can't recall how many miles, maybe 13K since. Hydraulic tank has always been a little above full and I left it that way.

I found the tank totally full in May 1000 miles into a 2000 mile trip, drained it off to normal level and have been watching it close since. Transmission has always said normal level till this weekend when it finally showed down 4 quarts. Maybe the float was sort of stuck or something. I drained off about 1.5 more quarts from the hydraulic tank as the level had creeped back up about 1/4 inch on the dipstick since my 2000 mile trip. I think I have put about 4500 miles on it since the May trip/original tank adjustment.

Total fluid transfer has been about 1.5 gallons.

Can you see the reducer from looking at the hydraulic fitting or is it inside the housing?
Thanks
Windecker

Windecker,

As I remember it's installed in line in the small fluid hose that feeds the spline (normally dry) area of the PTO. If I get a chance in the next few days I'll try to get a picture of mine and send it to you. I had to convert mine from dry to wet is the only reason I know about this.

[kurtsimon]

I have the same problem with my Monaco Executive with Cummins ISX and Allison MH4000. My hydraulic reservoir overflowed back in May. I had the excess fluid drained. Then I noticed last week that my trans was 6 quarts low. I added 6 quarts of Transynd, and after driving it 125 miles it still said 6 quarts low. No sign of leaks anywhere.

Today I took it to an Allison repair facility in West Sacramento who told me that the PTO shaft lube was probably forcing transmission fluid through the shaft seals into the hydraulic reservoir. He said the easy fix is to remove the tee fitting, but I note from other posts that this is needed for the PTO wet kit. He claims the area lubed by trans fluid is a shaft with seals on either side and no need for lube in between. They haven't started looking at it yet. The cost of repairs for PTO shaft failures appear to be extensive, from other posts here on Country Coaches.

Any advice I should pass on to the Allison tech?

Kurt

[Windecker]

Kurt,
As fate would have it, I literally just found this other thread last night. It may answer your questions as I think it did mine!

http://www.irv2.com/forums/f115/hydr...-a-303224.html

Looks to be a common issue.
Like your post suggests, I am also having trouble understanding how the drive end seal is supposed to protect fluid under pressure in both directions. Maybe once apart, it will be more obvious.

The QCC pump man said there is nothing that would protect the QCC pump from fluid pressure coming from the drive end (as in from the wet lube PTO drive). I guess it is possible that if the QCC pump drive end is leaking in both directions, it could be that the transmission lube pressure overtakes the QCC pressure and fills the hydraulic tank as we are seeing.

I am thinking though that the issue is in the PTO drive seal arrangement somehow.
That said, the QCC pump is easy to remove and reseal so for now, that is the direction I am going myself.

Part number for the hydraulic pump seal kit is: 10267 Part number for the pump drive mount gasket: 3916042 which is a Cummins number, I am sure others are available also.

Available from:
Gary Manchester
7315 W. Wilson Ave.
Harwood Heights, Ill. 60706
ph: 708-887-6320
Fax: 708-887-5009
manchester@qccorp.com


Windecker

Originally Posted by kurtsimon

I have the same problem with my Monaco Executive with Cummins ISX and Allison MH4000. My hydraulic reservoir overflowed back in May. I had the excess fluid drained. Then I noticed last week that my trans was 6 quarts low. I added 6 quarts of Transynd, and after driving it 125 miles it still said 6 quarts low. No sign of leaks anywhere.

Today I took it to an Allison repair facility in West Sacramento who told me that the PTO shaft lube was probably forcing transmission fluid through the shaft seals into the hydraulic reservoir. He said the easy fix is to remove the tee fitting, but I note from other posts that this is needed for the PTO wet kit. He claims the area lubed by trans fluid is a shaft with seals on either side and no need for lube in between. They haven't started looking at it yet. The cost of repairs for PTO shaft failures appear to be extensive, from other posts here on Country Coaches.

Any advice I should pass on to the Allison tech?

Kurt

[BarneyM]

Originally Posted by kurtsimon

I have the same problem with my Monaco Executive with Cummins ISX and Allison MH4000. My hydraulic reservoir overflowed back in May. I had the excess fluid drained. Then I noticed last week that my trans was 6 quarts low. I added 6 quarts of Transynd, and after driving it 125 miles it still said 6 quarts low. No sign of leaks anywhere.

Today I took it to an Allison repair facility in West Sacramento who told me that the PTO shaft lube was probably forcing transmission fluid through the shaft seals into the hydraulic reservoir. He said the easy fix is to remove the tee fitting, but I note from other posts that this is needed for the PTO wet kit. He claims the area lubed by trans fluid is a shaft with seals on either side and no need for lube in between. They haven't started looking at it yet. The cost of repairs for PTO shaft failures appear to be extensive, from other posts here on Country Coaches.

Any advice I should pass on to the Allison tech?

Kurt

Kurt,

There must be a Flow Restrictor installed in the line going to the spline section (normally dry section) of the PTO. If this is not installed trans fluid will flow into the spline area faster than it can drain out (the drain hole is very small for some reason) which will cause enough pressure to generate and this will force trans fluid past the hydraulic pump seal and eventually into the the hydraulic reservoir. Changing the pump seal will not fix the problem. I've attached a picture with the Flow Restrictor circled in red for your use. The restrictor is just a small brass fitting with a very small hole for the fluid to pass through. If you don't have this you need to install it to solve your problem.

jdrv1.com sells the wet kit and may be able to get you the restictor.

http://www.irv2.com/forums/attachmen...1&d=1541631317

[Windecker]

Thanks for the drawing and info Kurt.
I have a fitting that looks similar to this but will have to remove it to see if it is just a union or actually has a restrictor in it.

I can't read that part number very well, can you see it on your original better? Looks like 379964 but not sure.
Thanks
Windecker

Originally Posted by BarneyM

Kurt,

There must be a Flow Restrictor installed in the line going to the spline section (normally dry section) of the PTO. If this is not installed trans fluid will flow into the spline area faster than it can drain out (the drain hole is very small for some reason) which will cause enough pressure to generate and this will force trans fluid past the hydraulic pump seal and eventually into the the hydraulic reservoir. Changing the pump seal will not fix the problem. I've attached a picture with the Flow Restrictor circled in red for your use. The restrictor is just a small brass fitting with a very small hole for the fluid to pass through. If you don't have this you need to install it to solve your problem.

jdrv1.com sells the wet kit and may be able to get you the restictor.

http://www.irv2.com/forums/attachmen...1&d=1541631317

[BrianGlenn]

Here are a couple of pics from my PTO conversion to wet. The restrictor is the straight brass section before the 45 and 90 degree brass fitting.

You can also see the wet spline drain hole allowing the fluid to drain back to the gear area of the PTO and into the transmission.

Part number is 379964 Flow Restrictor - from my "AK Wet Spline Installation Kit".

Hope the pictures help,
Brian


EDIT - PS The fitting is tucked between the PTO and the tranny. Getting a wrench on it while the PTO is installed will be tough. A visual inspection is the most that I would do with the PTO installed.

[kurtsimon]

Thanks all for the great data.

My Allison tech tells me that the shaft between the seals doesn't have to be lubricated, and there is no drain hole, causing the high pressure against the wrong side of the seals. He says the damage to the splines on other iRV2 posts was more from moisture. He says the hoses for the wet kit can be plugged without risking excessive wear since the bearings on the other side of the seals are lubed. They did this a while back on another Monaco, and it seems to be working. We're going to try it and check it in a couple 100 miles and see how it works.

Kurt

[BrianGlenn]

Originally Posted by kurtsimon

Thanks all for the great data.



My Allison tech tells me that the shaft between the seals doesn't have to be lubricated, and there is no drain hole, causing the high pressure against the wrong side of the seals. He says the damage to the splines on other iRV2 posts was more from moisture. He says the hoses for the wet kit can be plugged without risking excessive wear since the bearings on the other side of the seals are lubed. They did this a while back on another Monaco, and it seems to be working. We're going to try it and check it in a couple 100 miles and see how it works.



Kurt

Strongly disagree! I can post all my pictures from a dry spline failure. They must be lubricated with either proper viscosity/type of grease or tranny fluid (wet).

No moisture ever in my failed PTO shaft.

Mode of failure is metal to metal galling/fretting destroying the splines.

Find another tech!

[TTD]

I do believe that moisture could get in on the original dry PTO setup because I don't believe there is any gasket between the PTO and the HYD. Pump.

I believe it's only when you go to the Wet PTO that you get a gasket between the two items?

Regardless... the tech is correct that you do not need to lube the connection between the PTO and the HYD pump to benefit the bearings... but that is not really the issue. You are lubricating the spline connection simply because you have two metal pieces in contact with each other and without lube, they will wear out. If you don't go with the wet spline, then you have to apply lube every so often.

And yes, it will work dry for a period of time (as most of us have proved it seems to work for about 30,000 miles). I had 33,000 miles on mine and caught it just in time as the PTO splines were in real bad shape.

[Windecker]

Kurt,
Sometimes the internet folks can work something out of nothing, us included but I would go with the forum folks on this one.
Just my 2 cents.

I think I have just a union and not the restrictor fitting. I am defiantly going to check though. Not sure how it has made it this many years, this many miles before causing an issue
Windecker

Originally Posted by kurtsimon

Thanks all for the great data.

My Allison tech tells me that the shaft between the seals doesn't have to be lubricated, and there is no drain hole, causing the high pressure against the wrong side of the seals. He says the damage to the splines on other iRV2 posts was more from moisture. He says the hoses for the wet kit can be plugged without risking excessive wear since the bearings on the other side of the seals are lubed. They did this a while back on another Monaco, and it seems to be working. We're going to try it and check it in a couple 100 miles and see how it works.

Kurt