Diff fluid recommendations

[MaineShark]

What fluid do y'all recommend? Additives? Since I don't know how long it's been since the fluid was last done, I figure I should change it, to be safe.

Joe

 

[Tom73]

Go to your chevy dealer and the their diff fluid along witht the posi additive.

tom...

 

[Stallion]

How do you know when you need to change the differential fluid? And is this an easy task just to do on a Sunday afternoon?

Thanks!

 

[Dave L.]

TR - Since you just purchased your car,I would definitely change the diff fluid. Here is how I change mine. I will drive the car breifly to warm up the diff oil so it flows better. I raise the rear of the car and remove the spare tire carrier. Remove the plug on the back of the diff housing,it's on the passenger side of the housing pointing back,If I remeber correctly just use the end of a 3/8" socket extension. Then,using a suction gun(refer to picture), suck out the old oil. You will need 3 bottles of GM# 1052271 and 1 additive GM# 1052358. Using the suction gun,suck the oil out of the bottles one at time and shoot the oil into the rear until it reach's the top of the fill hole. You will use almost the entire amount of oil. I always put the small bottle of additive in first,followed by the 3 larger bottles. Put your spare tire carrier back on and away you go. I change mine every 2 years.
You can purchase a suction gun at any auto parts store for about 10-15 bucks.

Dave

edit: after checking my records,You will use a small portion of the 3rd bottle not the entire amount.

 

[page62]

This is all correct, except the '79 and earlier Vettes only use 2 bottles of diff fluid and 1 bottle of additive. They changed the diff in 1980.

I did mine recently and it got rid of the clunking caused by sticking posi clutches. For once, a cheap and easy fix!

 

[MaineShark]

Thanks for the info on #'s and capacities. Guess I should wait until the weather gets better, so I can drive it to warm the fluid.

Now if that ain't a good excuse to go for a drive, I haven't heard one!

Joe

 

[Stallion]

TR - Since you just purchased your car,I would definitely change the diff fluid. Here is how I change mine. I will drive the car breifly to warm up the diff oil so it flows better. I raise the rear of the car and remove the spare tire carrier. Remove the plug on the back of the diff housing,it's on the passenger side of the housing pointing back,If I remeber correctly just use the end of a 3/8" socket extension. Then,using a suction gun(refer to picture), suck out the old oil. You will need 3 bottles of GM# 1052271 and 1 additive GM# 1052358. Using the suction gun,suck the oil out of the bottles one at time and shoot the oil into the rear until it reach's the top of the fill hole. You will use almost the entire amount of oil. I always put the small bottle of additive in first,followed by the 3 larger bottles. Put your spare tire carrier back on and away you go. I change mine every 2 years.
You can purchase a suction gun at any auto parts store for about 10-15 bucks.

Dave

edit: after checking my records,You will use a small portion of the 3rd bottle not the entire amount.

Okay, sounds like something I can do. Thanks!!

 

[born2saw]

A couple of the guys in my Corvette club recommend changing it every year, & I think that is also the GM recommendation. I will change it when I clean her up this spring. I got a 50cc syringe at work & will attach a plastic tube to it to get the fluid in and out. Total cost $0.00!!!! I'm not sure how well it will work and it may be a bit slow, but sometimes working at a hospital is really handy.

 

[78SilvAnniv]

We'll use our shopvac

Kenny has modified a bucket with a lid for sucking liquids. We first used it to change out my tranny fluid and it worked great. Granted it took several applications before I felt the fluid was mostly changed.
Torque converter fluid does not come out, it just gets diluted with the new fluid. After several treatments with the shopvac bucket sucker the fluid is mostly fresh.

You'll need:
Bucket with lid.
Cut a hole in the center of the bucket lid that snuggly fits the shopvac hose. (use duct tape if the hole has gaps)
Cut a smaller hole half way between the shopvac hole and the lid edge that snuggly fits a small diameter flexible tube.
Insert shopvac hose in its' bucket hole.
Insert flexible tube hole in its' bucket hole.
Insert free end of flexible tube into liquid.
Turn on the shopvac. (not on blow!)

Since we don't have a suction gun, I think we may just gravity feed with a flexible hose and funnel held above the rear end.
Heidi

 

[JohnZ]

A couple of the guys in my Corvette club recommend changing it every year, & I think that is also the GM recommendation.

From the Chevrolet Chassis Service Manual: "The rear axle lubricant does not require changing for the life of the vehicle. If additions are needed, or when re-filling the axle after service procedures, use lubricants described above" (GL-5 multi-purpose hypoid gear lube, or GM Positraction lubricant plus GM Positraction Additive for axles with Positraction).

 

[78SilvAnniv]

Fluid changes...

From the Chevrolet Chassis Service Manual: "The rear axle lubricant does not require changing for the life of the vehicle. If additions are needed, or when re-filling the axle after service procedures, use lubricants described above" (GL-5 multi-purpose hypoid gear lube, or GM Positraction lubricant plus GM Positraction Additive for axles with Positraction).

Is this specific to your year of vette John, or is it general for all vettes?
I'd like to know so I don't do something I don't have to. (if it ain't broke, don't fix it)
Heidi

 

[Dave L.]

John - I see those 'suggested' interval changes all the time from GM. I don't think I agree with any of them. I,personally feel that periodic changes of fluid (not to the extreme) is cheap insurance in avoiding costly repairs,especially concerning the rear axle,trans and engine oil. My 2 cents..............

Dave

 

[born2saw]

Originally posted by JohnZ
From the Chevrolet Chassis Service Manual: "The rear axle lubricant does not require changing for the life of the vehicle. If additions are needed, or when re-filling the axle after service procedures, use lubricants described above" (GL-5 multi-purpose hypoid gear lube, or GM Positraction lubricant plus GM Positraction Additive for axles with Positraction).

Per the 1975 Chevrolet service and overhaul manual supplement (that's a mouthful):

However, if vehicle is used to pull a trailer, change lubricant every 15,000 miles.

Now I don't pull a trailer, but I might consider the kind of driving I do 'severe use' (It sits a lot, then gets driven on the weekend). I have a driveline lag I thought was the U-joints, but my mechanic checked them all and says they are all tight. A club member said he had that feeling in his Vette before he changed the fluid. That said, I will change the fluid this spirng, but I may only do it every few years. As BURGLAR said, it can be cheap insurance.

BTW, the manual also says cvhange the oil every 6 months or 7500 miles, I don't think I will follow that either.

 

[MaineShark]

I'm correct in assuming that all Sharks have Positraction differencials, correct?

Joe

 

[Dave L.]

Joe... Yes

Dave

 

[JohnZ]

Posi was an option in '68 and '69, became standard in '70.