Allison Seals and Oil

[KaiserM109]

While getting ready to put the transmission I got from Glen at BFR Metals into my M923A1, I noticed that the front seal was starting to leak; not surprising with a 30 yr. old transmission. I have spent literally hours getting the part number for that seal: Allison # 23016643. Napa says that’s a Detroit Diesel number and that theirs is 32331. It is a 3.25 ID and 3.881 OD seal; $42.89 at Napa, $19.78 at Transtar Industries. Call around; it is supposed to be a common part.

While I had the experts on the line at Allison I asked them about what kind of oil to use. He said "get the military stuff out!" I was told that they no longer use the term “Dextron III” because they are no longer affiliated with GM; just use ATF or better yet to get the authoritative answer go to http://www.allisontransmission.com/parts-service/approved-fluids and select the red tab on the right for ON-HIGHWAY-FLUIDS. The man I talked to recommended ON-HIGHWAY because this more closely matches the way we are likely to use the truck. You will see a big block with three tabs at the top, TES 295, TES 389 and TES 468. TES 468 is for hybrid transmissions, so ignore it. TES 295 is for synthetic oils and TES 389 is for non-synthetic, you take your choice.

The military oil, which is probably 15W40, combined with super cold weather may be why my original transmission failed. He thought that the oil may have thickened too much and dried up a pump in the low gear pack. The MT654CR transmission, which is military only, has a different type of low gear arrangement than others.

For more information on the transmission go to http://www.allisontransmission.com/parts-service/faq-service-tips, click on the "FLUID AND FILTER INFORMATION" tab and pick the top selection. This will pop up a long document. Go to page 24 and page 25 for information on oil change frequency.

If you need to call someone about your transmission there are 3 numbers you will need to tell them. They can be found on a plate about the size of a business card on the right side of the transmission at the back of the main body just above the oil pan. Don’t be confused by any other tags, like a re-build tag bolted to the PTO port cover. At the bottom should be the numbers/letters MT654CR which is the model number. At the top there is a 10 digit number which is your unique serial number followed by an 8 digit number that is the assembly information. On my transmission out of an ’84 M923 that last number is 06885292 and is probably the same on yours. Parts for an MT654CR are not on Allison’s electronic catalog; dealers will have to look it up on paper.

If all this fails, go to http://www.allisontransmission.com and look around or call them at 1-800-252-5383.

One more thing, if you do decide to change this seal or are unlucky enough to have the torque converter fall out, like we were, you may have a “devil of a time” getting it back in. I asked how they do it at the factory. I was told that they stand the transmission on its tail and hang the torque converter (TC) by three chains from a hoist. There are 2 splined shafts that you have to line up by lowering the TC and turning it. Then the fun begins!! There is a pump that engages two flats on the TC which turns easily. If you don’t have the TC lined up and put pressure on it, the pump will turn with it and not line up. They bounce the TC up and down just a little by squeezing the chains together and turning the TC while it is up. It is up to you to figure out how you manage that. I’ll let you know how it works out for me.

 

[panzerwillie]

thank you for the INFO...

 

[5tonman1971]

Good post! There's alwYs a lot of questions about what fluid to replace the military stuff with.

 

[davo727]

Very nice, Thankyou sir

 

[trooper632]

How do you flush out all of the 40 wt oil from the torque converter before you add the ATF, or do you just fill it up and run it

 

[KaiserM109]

How do you flush out all of the 40 wt oil from the torque converter before you add the ATF, or do you just fill it up and run it

I didn't ask, but from past experience, just pull the plug and set it aside with a catchpan under the pan. Then, without starting the engine, turn the transmission over a dozen times, or so. You can do that by disabling the engine and cranking it.

After that, don't worry about it. I have the torque converter out, so I will get most of the fluids out of it by standing it on end. I will also blow out all of the transmission cooling system and change the filter. Next, I will put regular, cheap ATF in it and run that for a while. In about 6 months (realistically a year or so) I will drain it through the pan and put synthetic in it.

If you get the majority of the fluids out, I think 17 - 18 out of 27(?) quarts, you will be doing well. The only time I think you need to do better than that is if your fluid smells burnt, and you probably have worse problems than that.

Arlyn

PS If you have the transmission out, it is a real good idea to change the front seal. They go bad primarily from age and it would be a real pain to have to pull the transmission for that seal only. It will leak into the clutch housing and drip out the fording plug hole (which should be un-plugged for normal operation).

 

[djhenley]

Awesome info, but what oil did you put in yours? Jeff

 

[BKubu]

I have posted previously on this. I have taken multiple trucks to an Allison dealer/service center and they recommended Dextron III (admittedly it was multiple years ago so I guess that has changed) or Transynd (I opted against it because of the extra cost). I had 10W oil in my transmissions and they recommended changing it (they told me it was 10W...I just knew it was not ATF). How do you get it out? Multiple transmission fluid swaps. Each time, you end up with a higher percentage of whatever fluid you choose to use (and a lower percentage of the old fluid). Guys who apparently knew more than me swore that 10W or 15W40 was fine...even said an Allison tech told them over the phone it was fine. Whatever. I know what I was told in person by an Allison tech. I used to ALWAYS change the fluid in my transmissions as soon as I got a truck. I have recently been more lazy due to work and family obligations and have not had any problems. I can only repeat what I was told in person by an Allison tech. Others can believe what they want and, until I hear differently from an Allison tech, I am going to keep moving forward with what I was told. I will add that they never told me that 10W or 15W40 were bad...only that they recommended different fluids.

 

[KaiserM109]

Dextron III, 10W, 15W40, ... This discussion will never end!!

For me, I'm going cheap ATF this flush and synthetic on the next. Having paid $375 for a 16 mile tow, $500 for a replacement transmission and gone through this, I'm going to go with ATF not 15W40 which is what is in that bucket of oil drained from the torque converter.


Sorry about the crosswise thumbnail, I couldn't get it deleted. Maybe the moderator can help.

 

[LiqTenEXp]

I went to to ATF and haven't looked back. I have only done one flush but really enjoy how much better the transmission shifts up/down and seems to downshift under heavy load much better.

I used this: http://www.napaonline.com/Catalog/C...ulk-Dexron-III-Mercon/_/R-NRI75203_0006505653

for 65 dollars it was a good deal. You need 1 bucket to do the fluid swap (without converter) so it works out perfect.

 

[Artisan]

I found an Allison Repair shop in SO Calf that I would run to
from now on if I needed a tranny rebuilt when u are ready. I am sure there
not into selling parts, just rebuilds and installs. They have guys
sending them transmissions from all over the country weekly
and they have a dyno.

PM me for details.

( I am really happy w/ their service, not a shill, just want to share )

 

[Scott3398]

im in the process of changing the trans oil and im replacing it with Amsoil Torque drive which is what they recommend for the heavy duty transmissions.

 

[KaiserM109]

Here's why I changed the seal.

We had to stand it on its tail and lift the torque converter up and down with an engine hoist to get all the splines and the front pump to line up.

The good news, for you guys who have to do this, is that when it is all bolted up snug with NO oil, the torque converter can be turned through the fording drain hole with your finger in order to line up the bolts to the flex plate (flywheel for you manual transmission guys).

Also, the method the TM gives for not losing the bolt between the flex plate and the engine (really a bad thing!) doesn't work; surprise you? What we did was find a 4" long plastic tube that would fit tightly over the head of the bolt and use it to place it into the hole and turn several turns. We also barred the engine with a 1 1/8" socket on the front of the crank shaft. It took ~30 lb-ft to turn.

All I have to do now is hook up the output shaft, tubes and controls and fill 'er up!