: Save the diffs!



GEndo
06-30-04, 10:41 PM
After reading about some of the troubles with the rear differential, I got my V on the lift today to change the fluid. 4600 miles on it with no signs of leakage. Removal of the drain plug revealed some very black gear lube and a significant amount of thick, metallic paste around the plug magnet. The amount of the build-up seemed to be excessive compared to other vehicles I've worked on. Refilled with 1 1/2 quarts of Mobil1 75W90, did the figure 8 driving pattern eight times, sounded fine.

Based on what I saw, I'd recommend changing the fluid alot sooner than the 25k point listed in the owner's manual.

Dreamin
07-01-04, 04:42 AM
Thanks for the info...

I assume you used synthetic, and I thought I read somewhere that Mobil 1 does not meet GM's spec for diff oil (9986115), and I thought the diff was a "life-time" fill... not that you shouldn't change it often, I just didn't think it was recommended at 25K? maybe i'm just going senile :bonkers:

StealthV
07-01-04, 07:01 AM
The factory rear end lube is $27 per quart. :suspect:

Dreamin
07-01-04, 02:06 PM
Yes it is... costs me ~$60 for factory diff fluids alone for my Z06... there's an additive that you have to get for that car also. Luckily I've only done it twice, every other time it's been time to change the fluid, the diff develops a leak and the dealer changes the fluid for me. :rolleyes2

I believe Pennzoil meets the GM spec.

GNSCOTT
07-01-04, 04:39 PM
The GM additive keeps the rear from chattering. It is the foulest smelling of all the automotive fluids.

Dreamin
07-01-04, 04:52 PM
Yes, good stuff that additive...
http://zeemr.home.comcast.net/Additive.jpg

But looking at the CTS owners manual, they dont mention the need for an additive... I believe the V diff is different from the C5 diff.

StealthV
07-01-04, 06:07 PM
When I picked up my car, I had the dealer gather everything I needed for the rear axle lube change. They gave me -

Three quarts of #12378261 GM Synthetic Axle Lube SAE 75W-90

One 4 oz. bottle of #1052358 Limited Slip Axle Lubricant Additive (shown in the pic above)

When the V hits 1,500 miles after this upcoming holiday weekend, I'll take some pics and do up a little how-to on changing the rear lube.

WhiteLightning
07-02-04, 07:06 PM
My parts guy disagreed with me...

He said its regular fluid and the additive or if you have the synthetic then no additive.

What's the scoop. I intend to change tranny and rear diff this weekend while I have her in the air for the BMR "anti-hop" kit.

WL

Dreamin
07-03-04, 03:34 AM
That makes no sense... the additive and the "synthetic" part of the diff oil are doing different things... the additive is specifically for the Limited Slip clutch plates (lubricates them and prevents chatter), while the synthetic oil is for the whole diff, and has all the advantages (or disadvantages) that synthetic oils have over dino oils. They are definitely not incompatible. (Though there are a few synthetic diff oils that include their version of the additive, i.e. Amsol.)

The CTS owner's manual clearly says use synthetic diff oil... it does not list the additive as a requirement.
For comparison, the vette manual says the additive must be used:
http://zeemr.home.comcast.net/diff.jpg

With that said, the additive certainly will not hurt the diff... it can only help. I'd use it.

StealthV
07-03-04, 09:47 AM
Does a base CTS have a limited-slip diff?

Cal
07-03-04, 10:28 AM
I think I chewed mine last night. At 115 or so the thing didn't want to go into 5th, really weird. Heard a bit of a whine coming home later.

Ah well, off to the dealer.

globed70
07-03-04, 01:24 PM
I think I chewed mine last night. At 115 or so the thing didn't want to go into 5th, really weird. Heard a bit of a whine coming home later.

Ah well, off to the dealer.

Funny Cal, mine has had a bit of trouble getting into 5th at speeds of 110+

And this has been from new. Let me know if you find anything. Thanks.

DgtalPimp
07-03-04, 03:51 PM
I think I chewed mine last night. At 115 or so the thing didn't want to go into 5th, really weird. Heard a bit of a whine coming home later.

Ah well, off to the dealer.
Did you mean 1:15 ? hahaha
(whos Cal?)

Dgtal (dgtalpimp@pimppdaddy.com)

6104696
07-03-04, 06:09 PM
Maybe it is a special fuel saving feature in the computer which uses the CAGS to force you right into 6th at that speed :crying2:


dhg

Cal
07-03-04, 07:45 PM
It sure wanted to go into R of all things.

Dreamin
07-03-04, 11:42 PM
who's cal?

too funny :D :D will never forget that line from the other post... :banghead:

2004ctsv
07-04-04, 03:42 PM
It sure wanted to go into R of all things.
Isn't there a selenoid that prevents shifting into R instead of 5th? Everytime I upshift into 5th, I think about it and probably hestitate the shift.

Cal
07-04-04, 06:47 PM
I think some people have noted that at high speeds it doesn't block you, I vaguely recall a post about that.

It sure wanted to go into R and did actually get there for a split second where I heard some unhappy noises (I never let fully off the clutch thank god).

I haven't driven the car since, heard that whine and am taking it into the dealer, I don't want to be dropping my ass end on the highway after the stories on here. Just a pain in the butt whether they fix it or not, and forget about getting a tow during the holiday weekend.