05 Alison

[yukon25008.1]

sold the yukon, and im picking up an 05 hd ext cab long bed with 103,000 on it its got an 8.1 and is a one owner

just curious whats the best fluid/service for it.i dont know its history..if it was done or not but im not gonna leave it go i definitly want to change filters and fluid

[05GMCZ71]

Have it flushed. Use whatever is recommended by Allison & GM.

[yukon25008.1]

I thought alot of guys were against flushes because of the pressure

[txab]

Then just do a complete fluid change out without flushing. Use whatever fluid Allison recommends for the trans. Conflicting information can be found on their website. The last I saw was that up through certain serial #'s should not use Dex VI. I would call their customer service line to get a definitive answer.

 

We've always used TranSynd fluid.

[05GMCZ71]

what pressure? In most cases they use the transmission pump itself to flush the fluid through it. It is safe.

[Mike G]

If you like to do things yourself, there is a very good how-to on here about a fluid transfusion, but I will have to dig up the location. The external filter gets changed at regular intervals, the internal is changed at rebuilds. I want to say that these run DexIII up until mid 06, when they changed to DexIV, but that should be in your manual (or as noted above).

--Mike

[yukon25008.1]

Thanks guys, i switched to dex 6 synthetic in my last 4l85e and it worked great, i thought the allison had a different fluid than the others.. rather thana shift kit i can have justin adjust/tune the allison like the other trannys cant i?

What about the tranfsfer case?

[kurt1993]

your set with dex 6 if anything my 01 would be incompatable but i went to GM got some Dex6 worked great.... also i think you have a drainplug on the pan if you want to drain it and add... id also reccomend droping the pan and changing the spin on filter and the internal i just did mine myself think im a quart low though lol

[kurt1993]

Thanks guys, i switched to dex 6 synthetic in my last 4l85e and it worked great, i thought the allison had a different fluid than the others.. rather thana shift kit i can have justin adjust/tune the allison like the other trannys cant i?

What about the tranfsfer case?

 

 

My manual says use the Autotrak II crap for the trans case.... so i think im gonna use that stuff, but i think you may be able to use dex 6 as a substitute? not sure

[jake111]

For an '05 Allison the best transmission fluid is a TES-295 rated fluid, such as Castrol Transynd or Mobil Delvac Synthetic ATF (make sure it's the TES-295 ATF). You probably have to go to a truck center or Allison dealer.

 

One step down, but still very good would be an old Dex-III Synthetic. Unfortunately, they won't say Dex-III now (licensing) but will say "for 2005 and older GM". Mobil 1 Synthetic ATF is a good choice, if it's still available.

 

Allison does NOT recommend Dex-VI for 2005 and older because they found it will ruin the seals over time. The seals were changed part way through 2006 to support Dex-VI.

 

Allison definitely does NOT recommend flushing. An acceptable method is to disconnect the cooling lines at the radiator, but this can be messy. A safe, acceptable method is to change what comes out of the pan (7.75 qts), put in new fluid, run for some period of time (10 minutes up to 25k miles, or sometime in between), then repeat. Allison considers 2 changes to be essentially a "complete" change, but of course, it's probably more like 75%. Do it a 3rd time if the fluid was burned or really old.

 

The original ATF that GM put in turns a dirty brown color. Don't panic, that's normal. A burnt smell or particles would indicate a problem. Also, the proper fill level is towards the BOTTOM of the hash marks (say 1/4th up when checking at 170*F); otherwise, the transmission may run hotter than normal and/or blow out the vent when over 200*F.

 

Probably the best filter you can get is made by, ta-da, Allison. Only available at truck centers or an Allison dealer. And it's surprisingly cheap (<$10). Other name brands are fine (Napa/Wix, Baldwin, etc.)

 

You can go to the Allison website for direct information.

 

Transfer Case - well, it's got some bearings and a chain. Just about anything will work. GM recommended (and it came with) Dex-III. Synthetic Dex-III is a step up. Transynd works well but is overkill (the bearings and chain aren't going to benefit). Some people (including me) switched to Mobil 1 Synthetic 5w-30 and claim is runs quieter.

 

There were 3 types of transfer cases:

1) a part-time 4wd with a manual shifter on the floor.

2) a part-time 4wd, essentially the same as above, but electrically shifted.

3) a selectable full-time 4wd unit, also electrically shifted/controlled, which has a button that says something like "Auto 4x4".

 

Unless you've got a full-time "Auto 4x4" button, you've got a "manual" TC. I don't think these came in any of the HD's (for sure not in the diesels). Only this case required the blue AutoTrak fluid because it's got a lot more than bearings and a chain.

[jake111]

Since we were talking about TC's, be aware that any time after 50k miles it may develop a pinhole leak. This is caused by a poor design where the internal pump is held by fingers that extend into the (soft) magnesium case. There are steel clips to prevent this "pump rub" but they wear or jiggle out of place and then it wears a tiny hole.

 

The leak is very slow and people often find out only after the TC is destroyed. Be sure to check the TC oil level, or for leaks, at every oil change.

 

The leak can be patched with JB Weld or similar. There are kits for the pump plate that provide wide ears to prevent the problem. GM came out with improved clips, but again, they probably aren't sufficient. If you get a rebuilt TC, check it carefully!!! They may have just covered up the hole instead of putting a new tail piece on. That's also a good time to put in a proper pump plate, if you plan to go more than another 50k miles.

 

Some have gone 100's of thousands of miles without the problem; some have gone less than 100k miles; many fail by ~150k miles.

[8.1HD/ALLISON]

Thanks guys, i switched to dex 6 synthetic in my last 4l85e and it worked great, i thought the allison had a different fluid than the others.. rather thana shift kit i can have justin adjust/tune the allison like the other trannys cant i?

What about the tranfsfer case?

 

 

Yes, Justin can adjust shift points. He did mine and I love it.

[yukon25008.1]

In the yukon i had auto 4x4 and i had to use the autotracII,

So in the pickupstrans case i can use mobil 1 motor oil??

What about the front and rear differentials?

[yukon25008.1]

A couple other techs i talked o said dex 6 synhetic was the only way to go...

[jake111]

In the yukon i had auto 4x4 and i had to use the autotracII,

So in the pickupstrans case i can use mobil 1 motor oil??

What about the front and rear differentials?

- Yes, Auto 4x4 uses AutoTrac II blue fluid.

- Yes, manual TC can use motor oil; GM originally used Dex III ATF and is a good choice if that makes you more comfortable. I never verified, but heard that GM backed off recommending Dex VI for the TC and instead recommends their manual transmission fluid. Again, I don't know for sure because I switched to motor oil. Even AutoTrac is ok. Bearings and chains just don't care that much. Seals do, and the subject only comes up when Dex VI is mentioned.

- Front differential call for 80-90 gear oil; rear gets synthetic 75w-90 gear oil. GM sells something commonly called "grape juice", I think because it is scented because it didn't smell good. It's expensive but great for both front/rear diffs. Another excellent choice for both front and rear diffs is Mobil 1 Synthetic 75W-90 LS Gear Lubricant, which is cheaper and in most auto parts stores.

 

Dex VI is a good choice for . . . late 2006 and newer GM transmissions. For 2005 and older, it's your choice to believe GM or Allison. Or just find a TES-295 fluid (e.g., Transynd or Mobil Delvac) which nobody can dispute as being the best.