TheDieselPage.com Forums  
2017 - TDP's 21st Anniversary
What's New: | Feature Articles: | Product Reviews: | Member's Area: | Subscribe:
Duramax 6600 Diesel Page | Advertiser's Section | Classified Ads | Photo Album | Diesel Books, GM Licensed T-shirts


Go Back   TheDieselPage.com Forums > Chevrolet & GMC 2500HD/3500 Light Trucks > 2500HD/3500 HD Trucks & Drivetrain
Register FAQ Members List Photo Album Mark Forums Read

2500HD/3500 HD Trucks & Drivetrain Discussion Forum for the 2001 & newer 2500HD/3500 Trucks, Transmissions & Drivetrain

Reply
 
Thread Tools Display Modes
  #21  
Old 04-02-2004, 10:13 PM
DonG DonG is offline
Enthusiast
 
Join Date: Jul 2000
Location: Washington
Posts: 145
Post

wxmn6,

The two sets of numbers refer to the thickness or viscosity of the oils. Very similar to motor oil like 15W-40.

The 75W-90 weight gear oil is what comes in your truck differential and is recommended most of the time.

The 75W-140 is listed in your operators manual as an alternative gear oil if your tow heavy loads in hot weather. Heavy loads would be 12,000 lbs. or above. Several people on this site feel that even when towing heavy, the 75W-90 will still be fine.

When towing 14,000 lbs. I use the 75W-140.

I hope this helps.
Don
__________________
2003 GMC 3500 SLE, D/A, EC, LB, 2WD, White/Pewter, DeeZee boards, 5th wheel
Reply With Quote
  #22  
Old 04-03-2004, 06:05 AM
jbplock
Guest
 
Posts: n/a
Post

Ditto's to Don post.

Also another point regarding the numbers in an oil viscosity spec…

The high number (90 in 75W-90) is measure of the oil’s viscosity when it reaches operating temperature and the low number is a measure of the oil’s cold temperature viscosity.

So, 5W-40 and 15W-40 oil have the same viscosity at operating temp but the 5W=40 will flow better when cold.

Conversely 75W-140 oil will be “thicker” when hot than 75W-90 oil but have similar cold temp performance.

[img]smile.gif[/img]
Reply With Quote
  #23  
Old 04-03-2004, 09:35 AM
wxmn6 wxmn6 is offline
Enthusiast
 
Join Date: Sep 2002
Location: Claverack, NY
Posts: 100
Post

Thanks for excellent information. It's nice to learn about something like that.

I am just curious that if both 75w-90 and 75w-140 have same cold weather performance (which I was concerned because I live in NY where we can see sub zero temperature during the winter), then would it hurt to go with higher viscosity if you don't do alot of heavy towing? I would assume that thicker oil would give more protection? Would it (140) actually do more harm than good (than using 90), or is it just that 140 cost more than 90?

With the information given earlier, I will be going with 75w-90, but just want to learn a bit more about it.

Do the front transfer case also use 75w-90 too? If I am not mistaken, the front transfer case does not have factory sythetic, correct? If I want to go sythetic, is there something else that I need to do (other than draining) to properly clean the case so it would not get contaimated with mixed fluid? Thanks.
__________________
2002 Chevy Silverado 2500HD<br />Ext. Cab SB 4x4 LS<br />6.0L/HD Auto.
Reply With Quote
  #24  
Old 04-03-2004, 09:47 AM
G. Gearloose G. Gearloose is offline
Enthusiast
 
Join Date: Oct 2001
Location: NE CT
Posts: 506
Post

Quote:
Originally posted by wxmn6:
Do the front transfer case also use 75w-90 too?
Hmmm, you should only have one...
__________________
1996 K1500 6.5, 1984 K5 6.2 Banks both \"Stock\" (tilting hand side-side like Sammy Davis in Cannonball Run)<br /><br />Got Boost?
Reply With Quote
  #25  
Old 04-03-2004, 01:49 PM
jbplock
Guest
 
Posts: n/a
Post

Quote:
Originally posted by wxmn6:
... I live in NY where we can see sub zero temperature during the winter), then would it hurt to go with higher viscosity if you don't do alot of heavy towing? ....

Does the front transfer case also use 75w-90 too? If I am not mistaken, the front transfer case does not have factory synthetic, correct? If I want to go synthetic, is there something else that I need to do (other than draining) to properly clean the case so it would not get contaimated with mixed fluid? Thanks. [/QB]
wxmn6,

I’m not an expert on this subject but from what I’ve learned unless you are towing big loads regularly it’s best to stay with the GL-5 synthetic 75W-90. Using the heavier 75W-140 when not needed can lower your fuel efficiency.

And yes last I knew the front diff comes with 80W- 90 mineral oil but you can switch to a GL-5 synthetic 75W-90 (the 4WD transfer case uses DEXRON III). However, GM recommends you have the “white” vent cover on your front Diff for compatibility with the synthetic oil. See Feb03 GM Techlink article for more info.

It’s also not necessary to flush or clean the diffs (front or rear) when doing a routine fluid change to synthetic – the fluids are compatible. Just remove the magnetic plug, drain and refill. Also clean the plug ... the front diff plug on mine had quite a bit of “goo” on it. A small amount of metal filings is normal. (see pics)

Personally I changed both front and rear diffs to Mobil-1 75W-90 at 5kmiles. I also changed the transfer case and Allison to Mobil-1 ATF.

A search of the forum will also turn up a quite a bit of info on this subject.

Hope this helps… [img]smile.gif[/img]
Reply With Quote
  #26  
Old 04-04-2004, 12:31 PM
wxmn6 wxmn6 is offline
Enthusiast
 
Join Date: Sep 2002
Location: Claverack, NY
Posts: 100
Thumbs up

Thanks for very helpful information!
__________________
2002 Chevy Silverado 2500HD<br />Ext. Cab SB 4x4 LS<br />6.0L/HD Auto.
Reply With Quote
  #27  
Old 09-19-2007, 10:41 PM
alaskanmax alaskanmax is offline
alaskanmax
 
Join Date: Jul 2007
Location: Alaska
Posts: 3
Default G80 rear end acts like open diff???

According to some folks on the forums it is said that if you lift both rear wheels on the d-max, and rotate one wheel the g-80 limited slip will act just like an open diff and the other wheel will counter rotate. With out opening up my cover on my rear diff or getting stuck how will I know for sure what my used truck has??? I can find no stickers on dash or door areas to say it has a g-80
Reply With Quote
  #28  
Old 09-20-2007, 03:37 AM
DmaxMaverick's Avatar
DmaxMaverick DmaxMaverick is offline
Administrator
 
Join Date: Apr 2001
Location: CA
Posts: 11,682
Arrow

Quote:
Originally Posted by alaskanmax View Post
According to some folks on the forums it is said that if you lift both rear wheels on the d-max, and rotate one wheel the g-80 limited slip will act just like an open diff and the other wheel will counter rotate. With out opening up my cover on my rear diff or getting stuck how will I know for sure what my used truck has??? I can find no stickers on dash or door areas to say it has a g-80

Look in the glove box. Your RPO sticker is there, and G80 will be on that list, if you have one.

If you raise both wheels and spin one slowly (tranny in P), the other wheel should turn the opposite direction. If you spin one very quickly, like a good kick, it will lock. You can also test it on a roadside shoulder, one wheel on the pavement, and the other on loose ground (less traction). You should feel it lock when you goose it and one wheel breaks traction.
__________________
1985 Blazer 6.2
2001 GMC 2500HD D/A
2014 Chevy Cruze Diesel - Fabulous car, no problems at all, but sold Nov. 2016 @ 55K miles.
dmaxmaverick@thedieselpage.com
Reply With Quote
  #29  
Old 09-20-2007, 10:24 AM
SoTxPollock SoTxPollock is offline
Enthusiast
 
Join Date: Dec 2004
Location: Texas
Posts: 678
Default

ALASKAMAX, where are you located? I may have seen your truck, seems to be the truck of choice where I was last week, sure miss those 50 degree days, came back to 90 degree Texas days.
One word of caution when the locker locks, if you are on slick hard surface be prepared to back off the accelerator or you could find yourself going around in circles. On an open rear end at least one of the wheels will tend to help you keep it straight, but if both start to spin the engine torque and rear differential torque will tend to make the truck back end slide to the right. Enjoy the truck.
__________________
02 2500HD LT D/A SB CC 4X4 BLACK, Westin stainless nerf bars, BW GN Hitch,Racor 60S post oem fuel filter, Oil Guard bypass engine oil Filter. All synthetic fluids. Kennedy boost valve, edge, Modified air intake,EGT & Boost digital gauge,TransferFlow combo fuel & tool box, Air Lift Suspesion Bags Rear & compressor with remote, Bilsteins front & rear, Frontier front replacement bumper.
Reply With Quote
  #30  
Old 09-28-2007, 09:36 PM
alaskanmax alaskanmax is offline
alaskanmax
 
Join Date: Jul 2007
Location: Alaska
Posts: 3
Default

I, and truck are both in Anchorage. Today, I recieved my copy of Differentials Identification, Restoration & Repair by Jim Allen and Randy Lyman. I have read most all in the past couple hours, so listen up everyone....buy a copy as this book is really good and will answer any questions on the AAM 11.5/Eaton G-80. ......Thank You to Jim and Randy
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -7. The time now is 11:18 PM.


Powered by vBulletin® Version 3.8.2
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Copyright 1996-2017 by TheDieselPage.com - All Rights Reserved