Mixing in the rear end - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Luvlegs · 10-04-2006, 12:16 PM

My mistake - while at parts counter, asked what rear gear lube to put in differential - he gave me one bottle - I asked if that was enough for a complete fill - he ran and grabbed another off the shelf. AFTER I put all of one and almost all the second in, I noticed he had given me one bottle of Mobile 80W-90 and one of 80W-140 - I never thought to check the two. All of the 140 went in and darned near all the 90.
Do I empty and start over or go with it for a while and then change out?

On the positive side, I also found that after a few taps with a hammer to loosen, the plug came out nicely using the end of a short 3/8" extension (I didn't have any square drives).

It's starting to look pretty so heres a quick pic too.

**Green Machine** · 10-04-2006, 01:16 PM

I don't think that is going to hurt anything, just a little thicker than you wanted - like a 80w-110. It might be a little stiff if you drive in cold weather. here in Iowa I like to run synthetic in the rear diffs, gets pretty cold here-guess I would run it for a while and change to synthetic, no big hurry. If the previous oil had been in there a long time this will clean it up before the next change. If you complain, the might give you some free lube for the next change ?

Luvlegs · 10-04-2006, 01:19 PM

just needed to hear the same thing I was thinking from someone else - at least no fire alarms were pulled! Thanks.

timcos · 10-04-2006, 01:35 PM

Just to jump in and not hijack the thread...

Just to make myself feel better...I have a 4wd...can I just remove the covers, replace the gasket and fill it with new synthetic? I ask because the fluid has not been touched for two years (as the truck sat still) and who knows how long before then it was changed? I am noticing no adverse condition right now.

Is it that straightforward...or am I missing something?

Thanks,

Tim

Luvlegs · 10-04-2006, 01:50 PM

There's really nothing else to it that I know of - I took off the old cover, caught the old fluid, let it drain all out - cleaned mating surface for the new gasket, I put on a little gasket sealer, bolted on the new cover, added fluid until it was at level of fill hole. Simple actually.

*wolfthing2000* · 10-04-2006, 02:05 PM

BE CAREFUL. If the truck sat for years, the inner axle seals may have dried out ( on some models) and the new synthetic could leak out. I would be darned sure there aren't any leaks for sure.

10-04-2006, 12:16 PM	#1
Luvlegs Registered User Join Date: Sep 2005 Location: Smith Mountain Lake Virginia Posts: 1,537	Mixing in the rear end My mistake - while at parts counter, asked what rear gear lube to put in differential - he gave me one bottle - I asked if that was enough for a complete fill - he ran and grabbed another off the shelf. AFTER I put all of one and almost all the second in, I noticed he had given me one bottle of Mobile 80W-90 and one of 80W-140 - I never thought to check the two. All of the 140 went in and darned near all the 90. Do I empty and start over or go with it for a while and then change out? On the positive side, I also found that after a few taps with a hammer to loosen, the plug came out nicely using the end of a short 3/8" extension (I didn't have any square drives). It's starting to look pretty so heres a quick pic too. Attached Images __________________ "A cat will almost always blink when hit between the eyes with a ball peen hammer" (you don't always have to state the obvious) Wear your PPE! You can eat with false teeth but you can't see with a false eye. 1959 Studebaker Silverhawk 350/400 1972 C10 L6 3OTT 2005 F350 - Built - whew!

10-04-2006, 01:16 PM	#2
Green Machine Senior Member Join Date: Jul 2004 Location: Estherville, Iowa Posts: 3,371	Re: Mixing in the rear end I don't think that is going to hurt anything, just a little thicker than you wanted - like a 80w-110. It might be a little stiff if you drive in cold weather. here in Iowa I like to run synthetic in the rear diffs, gets pretty cold here-guess I would run it for a while and change to synthetic, no big hurry. If the previous oil had been in there a long time this will clean it up before the next change. If you complain, the might give you some free lube for the next change ? __________________ 1968 C10 307 3spd Long Fleet ------ http://67-72chevytrucks.com/vboard/s...d.php?t=201103 1970 C10 305 Super T10 Long Fleet --- http://67-72chevytrucks.com/vboard/s...d.php?t=202285 1971 C20 383 TH350 Dana Posi ----- http://67-72chevytrucks.com/vboard/s...d.php?t=206894 2001 GMC Sierra 1500 C3 6.0

10-04-2006, 01:19 PM	#3
Luvlegs Registered User Join Date: Sep 2005 Location: Smith Mountain Lake Virginia Posts: 1,537	Re: Mixing in the rear end just needed to hear the same thing I was thinking from someone else - at least no fire alarms were pulled! Thanks. __________________ "A cat will almost always blink when hit between the eyes with a ball peen hammer" (you don't always have to state the obvious) Wear your PPE! You can eat with false teeth but you can't see with a false eye. 1959 Studebaker Silverhawk 350/400 1972 C10 L6 3OTT 2005 F350 - Built - whew!

10-04-2006, 01:35 PM	#4
timcos Chief Honcho In Charge Join Date: Aug 2006 Location: Bentonville AR Posts: 970	Re: Mixing in the rear end Just to jump in and not hijack the thread... Just to make myself feel better...I have a 4wd...can I just remove the covers, replace the gasket and fill it with new synthetic? I ask because the fluid has not been touched for two years (as the truck sat still) and who knows how long before then it was changed? I am noticing no adverse condition right now. Is it that straightforward...or am I missing something? Thanks, Tim __________________ 1992 1500 4x4 Shortbed 1984 Ford F250 Supercab Longbed 6.9L Diesel 1972 K10 Cheyenne Super Fleetside Short Bed - 350 - A/C 1971 VW SuperBeetle 1960 Wife 1984 Son 1986 Son 1989 Son Previous Trucks 1967 C10 SWB (1980-1981) 1971 C10 LWB (1998-2004)

10-04-2006, 01:50 PM	#5
Luvlegs Registered User Join Date: Sep 2005 Location: Smith Mountain Lake Virginia Posts: 1,537	Re: Mixing in the rear end There's really nothing else to it that I know of - I took off the old cover, caught the old fluid, let it drain all out - cleaned mating surface for the new gasket, I put on a little gasket sealer, bolted on the new cover, added fluid until it was at level of fill hole. Simple actually. __________________ "A cat will almost always blink when hit between the eyes with a ball peen hammer" (you don't always have to state the obvious) Wear your PPE! You can eat with false teeth but you can't see with a false eye. 1959 Studebaker Silverhawk 350/400 1972 C10 L6 3OTT 2005 F350 - Built - whew!

10-04-2006, 02:05 PM	#6
wolfthing2000 Account Suspended Join Date: Oct 2004 Posts: 1,276	Re: Mixing in the rear end BE CAREFUL. If the truck sat for years, the inner axle seals may have dried out ( on some models) and the new synthetic could leak out. I would be darned sure there aren't any leaks for sure.



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