Hey all, I want to change the gear oil in my Diff. I remember a few of you guys were discussing this some time ago. I need to know which synthetic oil you used and the Posi-trac additive? Also how many litres does the rearend take? The guy at Partsource said he believes that it takes about 4 litres. I am a little skeptical about that. And, what is the part number for the gasket. Again, the guy at Partsource had no listing for a gasket, he figured that it would only need a silicone sealant.Somehow I doubt that .Any info would be great, ie. brands, part numbers, torque specs, helpful tips...etc.

 

I bought two of the synthetic bottles at Crappy Tire and I still had left over. And as far as the gasket goes, pick one up at the dealer. It will be a little more pricey than aftermarket, but really how often do you have to replace these things. And use the gasket, along with some RTV sealant. The RTV alone will not make a good seal.

 

What about the Posi additive for our cars? Did you have to go through the dealer for that too? What did everything cost approximately?

 

Don't put any Posi-additive in. It doesn't work well, it makes your posi slip. I'm not kidding. We're draining Paul's(Acceldz) rear end soon cause he put posi additive in and he's one wheelen peelin all over, we have to drain it wipe out all the old oil and posi additive and put in fresh stuff.

I've changed my rear end oil over about 6 times in the last 3 years, I like the synthetic stuff from Crappy tire. It takes less than two litres and go with the 80w90, thicker the better for rear diff's.

I have the 9 bolt rear and had a hard time sealing it without a gasket, I also had a warped cover so i had to get one of those too.

Get this the cover was less than the gasket.

Friggin GM...

Dave

 

Hmmm.... I dunno about NOT using the additive, It has to be there for some reason. Maybe it reduces wear on the posi-trac?

 

Well, I used to have the posi additive, as soon as I put it in it would slip, so i drained it, took it all out poured in fresh gear oil only, pound her and she locks both of them up every time. And I've heard of this happening to others, so I recommend going with out it. Posi additive is just a gimmic like
"B&M Trick Shift" does nothing but ruin the way it should work.

Thats my opinion, try the posi additive and let me know how she works ina couple months

Dave

 

Will do... Never heard of it not working.. maybe the synthetic oil screws up the posi additive?

 

I don't know why it would affect it. But Paul's is acting up now too, he says it has something to do with the way the 9 bolt rear gears are, cone shaped or something, but he's heard of it happening to 9 bolts alot too.

Additive works fine in my old man's 12 bolt, I don't know what it is.

Dave

 

I got the additive from the dealer when I picked up the gasket. I've been using the additive with no problems that I know of. I just figured they recommend it for a reason...nobody has ever really provided a good answer on this topic and it's come up many times in the other forums. I figured why chance it, both GM and the Haynes manual and the Chilton manual all recommend it.

 

YOU ARE NOT SUPPOSED TO USE ADDITIVES IF YOU HAVE THE BW 9 BOLT REAR END Do a search on the drivetrain board or ask for the latest TSBs at your local GM dealer. My posi worked when I got the car......... I changed the fluid using the additive..........My posi stopped working properly.

 

Hmmm... interesting.. I am gonna look into that

 

Nathan, post any good links that you find. I've had the additive in with the BW posi since last year and she still works fine.

 

I just got home from work, so I had stopped off to get the additive and gasket. I think they gave me the wrong gasket as it has ten bolt holes. Can I still use it? Also when I asked the parts guy about the additive, he said that they sell alot of it and that people swear by it. I asked him how much the synthetic oil was and he said that it was $23.00 a bottle and that I would need between 3-4 litres.(I know that PartSource sells it for $11.95 a litre.) He also said that with the additive, I don't need to use the synthetic.
What do you think, guys?

 

If it doesn't have the correct number of bolt holes than they must have given you the wrong one...or the rear end has been swapped out of your car in the past?!?

Based on what Acceld is saying, you should be okay with just the synthetic and no additive, but it really is your choice. I would say the additive is a replacement for sythetic though. And definately don't buy the synth from the dealer! Waaay too much!

 

The additive is GM part# 992694 it's about $8
The gasket for my BW was $12 at GM
The CDN Tire synthetic gear oil is only about $10 for 1L

 

You need to make sure to get the 7.75" gasket for the BW.
There were 3 different rearends used in thirdgens.
Most of the parts counter people don't know, so ask them to count the number of holes on the pic, on their computer. The BW is the only one with 9 holes. It is $13.85 including tax.
Most synthetic lubes have posi additive already in them. It should say on the bottle. 2 liters is lots.
If you use the synthetic, make sure to use a gasket and very lightly silicone both sides of it. It's much thinner then 80-90w gear oil and needs to be sealed.

 

Hey guys, I know this is old, but do you guys think I will be fine running 80W-90 Valvoline (non-synthetic) in my BW 9 bolt w/out the additive? My mechanic said no to the additive, and so do many people here. I just want to make sure it is safe with conventional gear oil not using the additive.--?? If there is something wrong in there, I will be able to hear it and take care of it before it's too late, right? So I really don't have anything to worry about? -89IRO

 

use amsoil 100% synthetic series 2000 gear lube 75w90 . you wont need an additive with this stuff. its got in it already. if you dont believe me, ask five7kid, hes an amsoil dealer.

 

Sorry, but my mechanic put in the valvoline today for me. Too bad for me it's not synthetic. I just got new bearings and seals installed along with a new gaskets. He told me no to the synthetic and to the additive. So the way I see it, if I have a problem (a noise coming from the rear) during like cornering or slowing down, that will tell me that I need the additive right? And I can always just throw a tube of the additive in myself if I have that problem. I just put it in the fill hole of the rear right? I know you are all going to ask me why my mechanic said no to synthetic, he just didn't want me to waste my money; and he's been in business for thirty years so he knows what he's talking about. So the conventional valvoline is in for now, and there's nothing I can do about it (or am going to do about it). Sorry about all that, but I just need to protect myself from all you synthetic crazy men. J/K! Anyways, so let me know about this additive. Thanks. -89IRO

 

I ended up using the non-synthetic gear oil 85W-140 and I also used the additive. The car is chirping with both wheels, so far. That was last June that I changed the oil, so it must be working fine with the additive. Hope this helps.

 

I cannot speak for the Borg-Warner rear- but ALL other GM posi's (i.e. Eaton, Auburn, Dana) need the additive to function properly- if it's not put in- the clutch plates will "grab" on-off when turning corners and make funky noises and wear the posi out at twice the normal rate. It is a "slip" additive to allow the clutches to only hold only as required- and not get "grabby" under light load conditions. I can only assume that the BW units use either a conical-type posi unit or different clutch materials.

 

I put 2 bottles of GM additive in this spring with the 75w90 synthetic (Orange goo) because I was having problems with some one wheel peel last year. SO i decided to go with 2 bottles of additive and things works like a top now.

 

i agree Eric. however, after talking with five7kid and reading some amsoil literature i have, their series 2000 gear oil already contains the additive. thats what i am using when i swap gears and put in a posi in the next couple of weeks.

heres a quote for the amsoil factory catalogue..."The Series 2000 Gear Lubes supply limited slip performance without aftermarket limited slip additives"

 

Yes- some of the aftermarket "performance" lubricants contain the additive already- I think Royal Purple may as well...

 

i have heard royal purple is makes good stuff too...but i dont know anything about it.

from what i have been reading and researching...amsoil appears to be the best of the synthetic lubricants. plus it is readily available to me at an excellent price.

 

 

I have a nine bolt BW posi-rear,been using synthetic Castrol 75W140 WITH the GM additive,altough the castrol bottle says the additive is already in....
Works fine for me!

 

Glad to see a fellow dutchman on the board finally.. hahahaha

 

 

I have the posi 9 bolt... here is my testamonial...

Before draining rear diff... one wheel wonder... drivers side would smoke, pass. side would not.. never ever...

Drained rear end, cleaned it out a bit and added the CT Synthetic Oil (I think it was 75W90), also added a bottle of the GM Posi Additive... figured "Why not, if the posi is shot then it's shot...it can only make it better or worse!!"

Buttoned it all back up and took her for a spin..... came to a nice light colored piece of pavement away from the main traffic... held the brake, held my breath and walked on it... tires broke loose, smoked poured out and I was off sideways :hail:

Took a run back around and was delighted to see two nice black stripes on the pavement...drivers side was slightly darker than the passenger side but a 10000000% improvement..

End of "my" story... maybe other stories won't turn out that way so don't blame me if ya put one of the most debated products on Thirdgen.org in yer rear diff and yer rear end gernades!!

 

.

 

Well ..... here is my break down


230'000 km's ( hard ones at that )

redline aditive ..... in my 10 bolt
1 blown motor
1 broken tranny
posi .......still rippin 40 footers .....for a kick

bottom line ... hehehe ..... I wish my motor and tranny had that frigging redline in it

 

80w90, no gasket...

we DO TONS of diff stuff at work, we dont use any gasket, just load the ultra copper on..NEVER leaks..

 

The debate was over additive use in the 9 bolts. If you don't use additive in a 10 bolt you are going to have problems.

 

Does John know that?

 

yes,90% of the time we dont use gasket..its fine, they dont leak...

 

the gear lube we have has posi additive already in it..some stuff made by kendall

 

opps ....got lost in all the hooopla LOL

 

Kill it! This dam thread won't die!!!

 

ok so what would I use in my posi rear diff. its from a 95 firebird formula?

 

This is a good thread...

One question: I have a 91 gta, my posi rips the ground evenly on both wheels, BUT i have NO idea when the last time the diff fluid was changed or IF EVER, I have the car almost 3 years and have not changed it... Do you guys think I should? Or just leave well enough alone?

 

If you don't know. Then I would definately change it. Whenever I buy a used vehicle, that is one of the things I do along with a complete tuneup etc.

 

Really.. ok I better do it this weekend then, thank for the help Kaz.

 

Not a problem at all, glad to have helped some.

 

Since it's a 10 bolt you should use additive. Buy some gear without any additive pre-added and then get some of the GM posi additive. It's only about $5-6 for a bottle. I'm pretty sure GM specs a synthetic diff fluid and posi additive for all 4rthgens now.