: Rear End Additive



Dave's V
04-10-05, 01:22 AM
I had to have my rear end replaced at around 1700 miles because it was doing the usual howl. Well they replaced it on Friday.

The invoice said the part number for the carrier was 10368780. They also had the fluid listed, pn 89021677.

Yes the additive was not listed. Fearing destruction of the new rear end, I asked the service manager. She asked the parts counter and a couple mechanics. They said the new fluid, (has a grape scent) doesn't require the additive.

I asked another sales manager today and he checked instructions for replacing the rear end. It lists all required parts, including the fluid, except the additive was NOT listed.

I checked the Redline site and found that their synthetic gear fluid that meets GL-5 standards doesn't require an additive. Is the grape scented stuff GL-5 standards?

Well I drove it for 300 miles so far breaking it in according to Cadillac instructions. I tried a few slow sharp turns in forward and reverse, accelerating on a slick surface, going over bumps, etc and the rear end performed flawlessly.

It was extremely quiet. It was nice to hear exhaust noise again. No whine/howl/grinding sounds.

I'm going to try to contact Cadillac and ask them if it requires additive. My dealer sells GMCs and Pontiacs so limited slip difs are nothing new to them. They use to charge an additional $7 for the additive.

Well, the car has 98,000 miles left on the regular/extended warranty so if they screwed up, I'll probably know about it.

The next question would be IF they are right (a BIG IF), would the additive cause any harm?

louiefl99
04-10-05, 04:49 PM
http://www.cadillacforums.com/forums/showthread.php?t=36329&page=3 scroll down to my post #56, there is a long explanation. Bottom line, I think your lube has the additive included.

If there is no additive the rear will scrub and howl at low speeds (less than 5 mph) with the front wheels turned hard lock. It will be worse in reverse.

Dave's V
04-10-05, 05:33 PM
http://www.cadillacforums.com/forums/showthread.php?t=36329&page=3 scroll down to my post #56, there is a long explanation. Bottom line, I think your lube has the additive included.

If there is no additive the rear will scrub and howl at low speeds (less than 5 mph) with the front wheels turned hard lock. It will be worse in reverse.

It sounds like some regular CTS may have a LS rear end. I would be pissed if my CTS didn't and the Europeans had one. I can't find the V on their site.

We need to slap a 50% import tax on everything Norway sends us though, just like they do to our CTS. I know the Germans like to put a 25% tax on imports. They can actually buy a MB or BMW cheaper here (same options) than in their own country.

louiefl99
04-11-05, 01:40 PM
gmpartsdirect.com shows 12378261 as synthetic axle lube and a note to "SEE NEW PART NUMBER 89021677". Now I'm a bit puzzled, did the new number replace the old evenly, or did the addition of a lS additive create the new number?

Either way, I do not have a definite answer.