Differential fluid

[HarrisonF]

Does anyone know the process for changing differential fluids front and rear?  I’ve got a 2020 2500HD 6.6 gas.  The manual says “see dealer” for fluid amounts and type. The manual also makes no mention of drain and full procedures.  Amsoil shows the fluid amounts for the front and rear. I changed the fluids and I have always filled until the fluid drained out of the fill hole.  However, the amounts I just put in are different than what Amsoil says and another poster on the forum. Any help is greatly appreciated. 

Edited December 8, 2022 by HarrisonF
Added the year

[newdude]

75w85 synthetic for the front, 75w90 for the rear.  You can probably get away with 75w90 in the front no problem.

 

Rear axle is 3.17 quarts.

 

Front axle is 1.9 quarts.

 

It also does say it should be 0-.25" from the bottom of the fill plug hole when checking the fluid level.  So filling it to where it starts to run and then letting it stop dripping out.  

 

 

Edited December 8, 2022 by newdude

[HarrisonF]

Thanks for the response.  Where did you find where it says 1/4” below fill hole?   My manual doesn’t say anything.   I put like 2.3 quarts in the front diff for it to drip out.  I’m assuming I’m over full now?

[newdude]

32 minutes ago, HarrisonF said:

Thanks for the response.  Where did you find where it says 1/4” below fill hole?   My manual doesn’t say anything.   I put like 2.3 quarts in the front diff for it to drip out.  I’m assuming I’m over full now?

 

 

Right from the service manual.  So at minimum its got to be 1/4" below the hill, or within that to up to the bottom of the hole.  

 

Were you on flat ground?  

Edited December 8, 2022 by newdude

[Black02Silverado]

Newdude is correct.  When I did my 2019 1500 Silverado I just filled until it dripped out of the fill hole like I have done to all my GM vehicles.

[HarrisonF]

11 minutes ago, newdude said:

 

 

Right from the service manual.  So at minimum its got to be 1/4" below the hill, or within that to up to the bottom of the hole.  

 

Were you on flat ground?  

Yes, I was in my garage.  Not on jacks or ramps.   Front diff took 2.3 or so and was barely dribbling out.  Rear diff took the remainder or the extra quart from the front, so .7 or so plus 3 other fresh quarts.  So the rear is at about 3.7 quarts and was not dribbling out.  It’s probably 1/8-1/4” below the fill hole. 
 

I don’t have a service manual. Where can I access that? 

[newdude]

33 minutes ago, HarrisonF said:

Yes, I was in my garage.  Not on jacks or ramps.   Front diff took 2.3 or so and was barely dribbling out.  Rear diff took the remainder or the extra quart from the front, so .7 or so plus 3 other fresh quarts.  So the rear is at about 3.7 quarts and was not dribbling out.  It’s probably 1/8-1/4” below the fill hole. 
 

I don’t have a service manual. Where can I access that? 

 

 

Helm is the only place I know of but the 2020+up HD one has not been released yet.

 

Owner Manuals, Service Manuals, Wiring Diagrams, Service Bulletins - Helm Incorporated

[Pryme]

44 minutes ago, newdude said:

 

 

Helm is the only place I know of but the 2020+up HD one has not been released yet.

 

Owner Manuals, Service Manuals, Wiring Diagrams, Service Bulletins - Helm Incorporated

How long will it take them to release that would you guess? 
 

in your own personal truck how long would you run the front and rear fluid in a new truck? Would you do it sooner or no? If not, what mileage?

 

thanks Newdude

[HarrisonF]

1 hour ago, Pryme said:

How long will it take them to release that would you guess? 
 

in your own personal truck how long would you run the front and rear fluid in a new truck? Would you do it sooner or no? If not, what mileage?

 

thanks Newdude

My 2018 1500 said 90,000 for differentials, trans, and transfer case.  45k if under severe conditions.  It also said 45k for 2500’s at the time.  My 2020 2500 doesn’t say anything except for 45k for transfer case.   So I’m taking that to mean 45k for diffs, trans and transfer case.  

[Pryme]

6 hours ago, HarrisonF said:

My 2018 1500 said 90,000 for differentials, trans, and transfer case.  45k if under severe conditions.  It also said 45k for 2500’s at the time.  My 2020 2500 doesn’t say anything except for 45k for transfer case.   So I’m taking that to mean 45k for diffs, trans and transfer case.  

Thank you. 
 

I was kind of wondering if it would be a good idea to do it the first time on a new truck sooner. That kinda thing. 

[slj2008]

My 2019 - i did Front/Rear/Trans & Transfer case at 50,000

[customboss]

On 12/8/2022 at 11:04 AM, newdude said:

You can probably get away with 75w90 in the front no problem.

I use Amsoil Signature Series 75w90 front and rear diffs  in lieu of the Castrol made 75w85 soy crap.  Which is not that bad but its hygroscopic, drain it and look at the water entrainment. 

[customboss]

23 hours ago, Pryme said:

How long will it take them to release that would you guess? 
 

in your own personal truck how long would you run the front and rear fluid in a new truck? Would you do it sooner or no? If not, what mileage?

 

thanks Newdude

I'm not a expert  GM tech like newdude but I have independently tested lubes of all types for over 40 years and 45,000 miles is a good guide for OEM quality fluids in differentials  if there is no other reason or stressors like heavy off road 4WD efforts, heavy towing, driving in and around deeper than rain level water on roads, dust, dirt, etc. Using a high quality synthetic will allow longer if kept clean, breathers sealed and in good repair etc.  Redline, AMSOIL from Black02Sillverado, Neo back in the day, RLI, Lubrication Engineers ( not always full syn but they make up for it with Nazi developed additives in petroleum products), some Pennzoil products that are specialty Marine use but work really well in PCMO apps.  

[Grumpy Bear]

1 hour ago, customboss said:

I use Amsoil Signature Series 75w90 front and rear diffs  in lieu of the Castrol made 75w85 soy crap.  Which is not that bad but its hygroscopic, drain it and look at the water entrainment. 

 

Which of the dozen Castrol offerings are you talking about? 

[customboss]

5 minutes ago, Grumpy Bear said:

 

Which of the dozen Castrol offerings are you talking about? 

The only 75w85 they ever made for GM. I can't remember the marketing code or name off top of head.  This is dated but its close. 

Castrol Syntran 75w85 .pdf Castrol Syntran 75w85 MSDS.pdf

Edited December 9, 2022 by customboss
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