: diff additive



First Class Motoring
05-29-07, 01:54 PM
hey guys,just got my car back from the dealer from installing a new diff.they did not put the additive in said it had a synthetic gear lube.should i put the additve in or is it ok with synthetic lube?thanks

ronr
05-29-07, 03:12 PM
hey guys,just got my car back from the dealer from installing a new diff.they did not put the additive in said it had a synthetic gear lube.should i put the additve in or is it ok with synthetic lube?thanks

You do need the additive (even with GM synthetic lube)
________________
Ron,

I am the service engineer for the CTS/CTS-V rear drive modules (RDM). I consulted with Sumie Thaker, the design engineer for CTS/CTS-V rear drive
modules to make sure that I provided the correct information to you.
Both the CTS and the CTS-V use synthetic fluid (GM p/n 12378261). All '04 - '07 CTS-Vs are equipped with limited slip RDMs so they all require the additive (GM p/n 1052358) in the required amount specified in the service information.
There is no external identifier for a limited slip RDM. The RPO for limited slip is "G80" and can be found on the SPID (Service Parts Identification) label. Since all Vs are equipped with limited slip, your vehicle requires the synthetic fluid and the proper amount of limited slip additive.
I pasted the service information document "Lubrication Specifications" for the '04 - '06 CTS/CTS-V at the bottom of this e-mail for your reference.

Please give me a call if you have any questions

Steve Underwood
Service Engineer - Driveline/Axle - Sigma, Kappa, Theta/Epsilon & Midsize Truck
MC: 480-210-1B2
VEC-Podium - Cube 1M12-23
30001 Van Dyke, Warren, MI 48090
Ph. (586) 575-4564
Fax. (586) 575-4000
e-mail - steve.underwood@gm.com

First Class Motoring
05-29-07, 03:18 PM
thanks.:thumbsup:

austin
05-29-07, 04:25 PM
>hey guys,just got my car back from the dealer from installing a new diff.they did not put the additive in said it had a synthetic gear lube.should i put the additve in or is it ok with synthetic lube?thanks


Hooooold on a minute... I just asked this very same question a week ago as well. The dealer said the same thing to me about the additive not needed due to synthetic fluid. Now i'm not too sure what is going on... Why would different dealers be telling the exact same story.. This needs further investigating.. Maybe the newer diffs are shipping with just the additive in them already??? Or GM's fluid now contains friction modifiers like other diff. fluid from other company's... And now the additive is not needed.

Here is the part number for the fluid they used; #89021677

dvandentop
05-29-07, 04:35 PM
unless they put royal purple in which alreayd has the diff additive in but i doubt they did

rand49er
05-29-07, 04:39 PM
Austin, that's the same lube they put in mine last July PLUS they put the above mentioned additive (PN 1052358) in. I have what I consider to be a superior dealer. Don't trust yours.

You NEED that additive!

First Class Motoring
05-29-07, 04:39 PM
does royal purple rilly have the additive in it?

dvandentop
05-29-07, 04:45 PM
i had it in my z06 for many miles and never had issues after i swapped to royal purple

ronr
05-29-07, 05:53 PM
89021677 replaced 12378261 and it DOES require the additive just like the other.

The root cause of the confusion at the dealers is (or should be) whether your car has a limited slip differential.

The other part of the email I received contained the following:
______________
Sumie,

The following e-mail has a couple of questions concerning '04 - '06 CTS-V RDM lubricant. To summarize the questions:
1. Do all CTS-Vs have limited slip RDMs, and if so, do they have the G80 RPO or is the limited slip RDM included in a CTS-V specific RPO? (I'm looking for an easy way to tell the dealer to find out if the RDM is an open or limited slip) - All '04 - '07 CTS-V (GMX-320 V) have LSD. G80 is the RPO for LSD.

2. It looks like both the open and the limited slip RDMs use synthetic lubricant, is that correct? - Both open and LSD uses synthetic Lubricant.
3. Does the limited slip RDM require an additive? - Yes. We add additive to synthetic lube for LSD applications.

4. Is there an external identifier for the limited slip RDM? - There is no external identifier for LSD. From VIN they can identify if axle has G80 - LSD.


I've attached a copy of the service information for lubricant specifications for '04 - '06 CTS (including V). Please take a look at it to make sure it is correct.

Please give me a call or send me a note back and I will respond to the e-mail.

Thanks,

Steve
__________
In the service documentation that was sent to me it clearly states that LSD's need the additive. The argument I got into with my dealer was that the mechanic couldn't confirm the car had an LSD (I'm thinking he was on LSD!) This is why the answer to my question contained the RPO code information.

Lindsay Cadillac
05-29-07, 06:15 PM
Here's the information from the service manual... It needs the additive...

Unfortunately you can't use the G80 option code to determine if the V has a limited slip differential, it's not on the SPID label. The problem arises when a dealer can't get their head out of their but to see that the car has a limited slip even though it doesn't have the G80 code...

Lindsay Cadillac
05-29-07, 06:21 PM
Here's the actual fluid change procedure from the service manual... It specifically mentions using the additive with a limited slip differential...



I can't believe this still comes up... :banghead:

ronr
05-29-07, 06:25 PM
Here's the information from the service manual... It needs the additive...

Unfortunately you can't use the G80 option code to determine if the V has a limited slip differential, it's not on the SPID label. The problem arises when a dealer can't get their head out of their but to see that the car has a limited slip even though it doesn't have the G80 code...

You're right on. I too found the G80 wasn't there but I thought they got that fixed with the '06 and beyond cars. The mechanic at my dealership was on a mission to prove me wrong about this. He already had egg on his face since he first filled my new diff with non-synthetic :want: so I had one up on him re: the synthetic and he was bound and determined to even the score on the additive. Good thing my service writer was in my corner and just insisted on the mechanic adding the additive.

First Class Motoring
05-29-07, 06:52 PM
so,does anyone know if royal purple has the additive in it?

Flyboy
05-29-07, 07:12 PM
Yes....I use RP......and it HAS the additive blended in already. (I spoke with one of the techs there)......very nice people BTW.

First Class Motoring
05-29-07, 07:17 PM
thanks.

rand49er
05-29-07, 09:09 PM
Yes....I use RP......and it HAS the additive blended in already. (I spoke with one of the techs there)......very nice people BTW.Jimmy, I know you recently posted this, but exactly what/which RP again is it? :hide:

Thanks. I may just do this in the near future.

thebigjimsho
05-29-07, 09:57 PM
so,does anyone know if royal purple has the additive in it?Yes, as does the Red Line gear fluids...

dvandentop
05-29-07, 10:44 PM
royal purple gear lube

First Class Motoring
05-29-07, 10:45 PM
thanks agian guys :worship:

austin
05-29-07, 10:49 PM
This is a big PITA!! Should i wait the 500-miles... or just drain it now, and add the additive and Mobile-1 synthetic gear oil. I hope the no additive doesn't lead to pre-mature whinning, or clutch damage. If i decide to go with Royal Purple i don't add the additive... right? :(

thebigjimsho
05-29-07, 11:24 PM
This is a big PITA!! Should i wait the 500-miles... or just drain it now, and add the additive and Mobile-1 synthetic gear oil. I hope the no additive doesn't lead to pre-mature whinning, or clutch damage. If i decide to go with Royal Purple i don't add the additive... right? :(If you are still under warranty, take the V to an independent shop and have them add the additive or refill it with RP or Red Line. Again, no additive needed with those 2fluids. Then take the bill to Cadillac and make them pay for it since they failed to perform proper maintenance. That's exactly what I would do if I were you right now.

ewill3rd
05-30-07, 06:45 AM
I believe the G80 issue is related to "packaging".
The V package and other options are lumped together so the G80 isn't added since it is already part of another options package.
Therefore it doesn't show on the SPID label like it would on a base car that had G80 installed.

On a base CTS you'd find the G80 RPO code but you won't on the V.
GM doesn't consider it "broken" so they are not going to "fix" it.
;)

I can't speak to those other brands, but the GM stuff doesn't have the additive and it does require it.
James posted the relevant documents.
I am not sure why some techs don't know how to utilize the information in the service manual, but it is right there anytime they care to read it.