06 Duramax Diesel Maintenance

[Stk1514]

I recently purchased a 2006 SIlverado 2500HD Duramax Diesel w/Allison Transmission. purchased form the Original Owner w/120,000 miles on it.

It now has 124,900 miles on it. ( I just use it to tow) Original Paint,  No Damage History,  Extra Cab Model.

 

Not sure if the Original Owner ever changed the Front & Rear Differential Fluids, and Transfer case fluids?

 

Original Owner would change Engine Oil at 5000 mile intervals ( Full Synthetic), and replaced the "External Allison Transmission" Filter and added a quart of Transmission oil.

 

Should I change the Front & Rear DIfferentail Fluids & Transfer Case Fluid?

If so what type of Fluids should I use? 

 

I've never owned a 3/4 ton w/ Diesel w/an  Allison Transmission

Thanks in advance for Suggestions,

 

 

[davester]

download the owners manual, it details the fluids to use and when to change them, it's free from gm/chevs web site.  Note, the transfer case will specify DexIII transmission fluid, and while DexVI is generally backwards compatible, it may cause problems with seals, so it's recommended to stick with a DexIII fluid.

 

And, IIRC, he should have also periodically drained/refilled the transmission when changing the external oil filter, not just change the filter and add a bit of fluid.  You may want to drain/refill the transmission if you aren't sure the P.O. has been doing it on schedule.

 

You may also wish to ask the P.O. if they did the pump-rub fix to the transfer case, and if they haven't, you may want to.  Google "gm pump rub" for more info on it.

[jake111]

First, everything Davester said!!!

 

For both the diffs, I like Mobil 1 Synthetic 75-90 LS.  The rear diff needs some (but not too much) friction modifier, so the gear oil that already has it (like the Mobil 1) is the easiest way to get it right.  Or you can pay something like 3x more and get genuine GM "grapejuice".

 

As Davester said, the transfer case needs Dex III and not Dex VI.  If it hasn't had an after-market pump rub modification, then it needs it.  I think GM might have one, but it's not as good as the after-market upgrades.

 

For the Allison, a TES-295 ATF is the best you can get (Castrol Transynd or Mobil Delvac; there are others).  Also very good would be a synthetic Dex III ATF (like Mobil 1 Synthetic ATF "for older GM" because they might not be able to advertise Dex III since that spec was retired).  Don't let a dealer talk you into Dex VI (could develop leaking seals later, unless your transmission was made after the "change", but you'd have to find that, and find your serial number).  Either way, TES-295 is best.  At 170*F, the proper fill level is about 1/4th up in the hot has area of the dipstick.  Filling it higher might cause the transmission to run hot.

 

Also, just replacing the external filter would cause only a few ounces to be lost, so for sure don't add a quart!!

[Stk1514]

It was suggested to use Amzoil for the Front & Rear Differentials & Transfer case, Does Amzoil contain friction modifiers for the differentials or does the GM supplement need to be used (in the rear diff)?

 

Thanks