I help my neighbors with basic maintenance on their van, a 2003 GMC Safari 4.3L. The diff has never been serviced at 120,000 miles but I don't want any liability issues/angry neighbors if doing the diff service this late can cause problems. It isn't making any noises and seems to run fine, and they are planning to keep this van forever. Although they depend on this van for all their transportation, they know they are neglecting this diff service and don't seem to care. Thoughts? Maybe check the condition of the fluid and go from there? Maybe just keep my mouth shut and let them deal with the consequences? Thanks
2003 GMC Safari 120k miles, too late for diff service?
- Thread starter DGXR
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I don't see any issues as long as it doesn't require a special additive for the limited slip (if equipped).
MolaKule
Staff member
I would replace the gear lube with a 75W110, such as Amsoil's SVG 75W110.
Unless the OEM requires a differential service on the maintenance schedule, I personally think differential service is overrated on vehicles that do not see towing.
120k mi is nothing, it's never too late. Also there are tons of pickup trucks and vans that have gone near 500k on the original diff fluid before letting it out on the bed. It's still fine at 120k. If you're not loading it up or towing a 90 would be okay but I'd still use a 110. If you're gonna make that 4.3 suffer use 140.
You need to be careful about this because even the G80 does not use limited slip additive, many people get very confused about this and it is a huge debate all over the internet.
What GM supposedly recommends now for G80's according to a guy I know at the dealer is 75w-90 and no longer the 80w-90, use GM 88900401 without any use of additive.
Yes this differential requires LS additive, which I have.
G80?
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I would service the diff for sure, not only does it lube the diff, but the hub bearings aswell. I would use any synthetic gear lube no less than 75w90. Be sure to clean the magnet at the bottom of the pumpkin, and be a swell guy and use a gasket instead of RTV like an animal.
The '03 Safari maintenance schedule only calls for checking the rear (and front) axle lube every 3k miles. No replacement interval. There's also no mention of an LS additive.
I first serviced the G80 differential on the '03 Safari at 115k. That was 13 years/60k mile ago. I refilled with Red Line 75w-90. This lube contains LS friction modifiers. I don't think there's any harm in having LS friction modifier in there.
I first serviced the G80 differential on the '03 Safari at 115k. That was 13 years/60k mile ago. I refilled with Red Line 75w-90. This lube contains LS friction modifiers. I don't think there's any harm in having LS friction modifier in there.
Maybe I was wrong about the axle requiring LS additive. LS additive won't hurt a differential that doesn't need it, but we already have the additive anyway... so unless we find out for sure it's not needed, it will go in. For terminology, it appears that "positraction" is a brand name for GM's limited-slip mechanism. I have the VIN for the neighbor's van but it doesn't have enough info for the axle spec, so I'll look for the RPO codes next.
GM RPO CODES - AXLES
Thanks for all the replies, will chime in later if we find anything interesting or useful.
GM RPO CODES - AXLES
Thanks for all the replies, will chime in later if we find anything interesting or useful.
The reason why it is controversial and a huge debate in regards to if it is a G80 is because the G80 has clutches in it of which additives may or may not cause issues with.
The RPO codes are located in the glove box, also you can contact GM through their social media email and request a build sheet and they will email it to you with the RPO codes and everything already broken down in a list for you.
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Is there another type of LSD that does not have clutches? I thought axles were either open, LSD, or lockers.
Not including the modern LSD systems that have an open differential and the computer applies braking power to the spinning wheel to transfer power to the gripping wheel.
Not including the modern LSD systems that have an open differential and the computer applies braking power to the spinning wheel to transfer power to the gripping wheel.
The G80 does have clutches. I don't know why LS additive isn't mentioned in recommended fluids in either the owner or service manuals.
I'm thinking it has something to do with the locking mechanics between a typical LSD and the G80 Gov-Lock.
I'm thinking it has something to do with the locking mechanics between a typical LSD and the G80 Gov-Lock.
If they don't seem to care, the best route may be to check the fluid level and inspect for leaks during regular service.
GM full-size trucks with the G80 option from at least that era on up used an Eaton Gov-Lok locker. It has clutches, but they don't do the same thing as LS clutches. A governor in the rearend senses slip and then locks the axles, unlike the traditional limited-slip that has preloaded clutches that "slip" during turns. The trucks took a different fluid than cars that had the traditional limited-slip.
I'm still confused after all these years of reading online posts and trying to decipher GM's spec numbers. But I do know that IF this van has the Gov-Lok, then no extra LS additive is needed. People seem to get by with fluid that already has it mixed in, but some actually seek out fluid with no additive.
Maybe someone with more knowledge of this model can give a definitive answer, but a quick check on Rock Auto suggests that it has the smaller 7.625" rear and the G80 is a Gov-Lok.
GM full-size trucks with the G80 option from at least that era on up used an Eaton Gov-Lok locker. It has clutches, but they don't do the same thing as LS clutches. A governor in the rearend senses slip and then locks the axles, unlike the traditional limited-slip that has preloaded clutches that "slip" during turns. The trucks took a different fluid than cars that had the traditional limited-slip.
I'm still confused after all these years of reading online posts and trying to decipher GM's spec numbers. But I do know that IF this van has the Gov-Lok, then no extra LS additive is needed. People seem to get by with fluid that already has it mixed in, but some actually seek out fluid with no additive.
Maybe someone with more knowledge of this model can give a definitive answer, but a quick check on Rock Auto suggests that it has the smaller 7.625" rear and the G80 is a Gov-Lok.
I know a guy at a dealership he looked it up in their system, GM no longer recommends the use of 80w-90 and instead recommends the use of 75w-90 and to not use limited slip additive.
He told me to use GM 88900401
Call your local dealership and confirm it through them is my recommendation.
Torsen LSD (it's used in the center diff for my GX460 for instance). I also installed one into a Tacoma rear diff, they are clutchless and use gears instead.
The owner's manual calls for GM 12378261 in both the front and rear axles.
GM 12378261 has been superseded by GM 88900401.
GL-5 75W-90 Synthetic Axle Lubricant - 1 qt 88900401 | GMPartsDirect.com
88900401 - GL-5 75W-90 Synthetic Axle Lubricant - 1 qt
www.gmpartsdirect.com
That's the part number specified for my 2001 Silverado 1500, as well as the 2003 Safari according to the manual I just looked up. Neither manual mentions anything special for G80.
The owner's manual calls for GM 12378261 in both the front and rear axles.
GM 12378261 has been superseded by GM 88900401.
GL-5 75W-90 Synthetic Axle Lubricant - 1 qt 88900401 | GMPartsDirect.com
88900401 - GL-5 75W-90 Synthetic Axle Lubricant - 1 qt
If you follow the link and expand a photo, you'll notice "New Grape Scent." I recall the stuff being something like $24 or more when I was looking to change. The factory fluid did have a lovely grape scent when I drained it.
