I did exactly the same a few months ago. Same oil and additive. Very happy with the results.

 

Hey MoFex, did you check from what you collected to see if it was a low fill from the factory? Just curious if others are experiencing the same thing. i am not sure if a half quart makes much of a difference, but it was a little disconcerting.

 

I did not measure the factory fill, but i think the level was OK.

 

I have an 08' AWD with approx 43,000 miles. Your comments have caused me to go ahead and do the fluid change on my rear dif. as well. My question as far as the additional additive goes, how do you know if the car has the limited slip dif or not ? I assume with mine not having the performance package, I will not have it ?

 

I believe if you have the FE2 suspension with AWD you have the limited slip

 

Look in the trunk, on the underside of the spare wheel well cover and look for the option code G80 on the service parts identification label.

G80 - Limited Slip Differential

ps - I have about 15,000+ miles on the AMSOIL Severe Gear 75W-90 in my CTS4, went in approximated 5,000 miles. Don't know if was low, I paid someone else to do change out both axles.

 

No G80 on my RPO code list.

Noob question alert.

So the CTS4 will have a front and rear differential?

Are the drain/fill specs the same for both the front and rear?

 

there's one question I never see answered in these threads;

where you lifting the vehicle from the rear only or were you using an acutal lift and/or had the car up on 4 stands on a level surface?


using the latter method is how you're supposed to do it. Raising only the rear will overfill the diff and will not remove all of the oil which might make it appear to be underfilled.

 

I had the car up on four stands ... but given that the differential drains from the bottom center, I don't imagine there's much oil held back if you lift from the rear.

 

1/2 a quart isn't a lot of fluid is it?

 

Plan to do the same on my 08 at 30k miles with AMSOIL SG. Love that stuff.

 

if the Dexron LS weren't $40-50 for 2 quarts, I'd use the OEM stuff. Just changing it for regular driving is the critical part in this case really, the added bonus being that the 'better' fluid is also < half the price

 

Good question. When it only holds 1.5 quarts is it seems like a lot to me ... but as far as if being low nearly half a quart is a problem in terms of how the differential operates, wear and tear, I don't know. All I know is that if the recommended capacity is 1.5 then I expect it to come from the factory with 1.5 ...

 

Does any of this information apply to a RWD differential (of course no Lim Slp)? It must have a meatball but is it the same fluid amount and (75W-90) viscosity? Bottom drain and side fill plug?

 

same drain and fill, same viscosity, capacity and whether you need to add some LSD additive may apply however.

 

 

What size hex did you use and also what did you use to pump it in?also how much of the 4oz slip lock did you put in? Thank you so much I hope your caddy it's driving great after the fluid change!

 

hopefully you get an answer...he hasn't been here since 2016

Bill

 

I did mine (front and rear) at about 60k and used Mobil1 synthetic differential fluid with the LSD additive in it already.
My car was shuddering when making a hard turn at a light and has been quiet ever since.
The back was easy to drain and fill. The front fill plug was a little hard to find and is located on the side facing the front of the car. I also did the transfer case fluid which I got from the dealer.
I know a mechanic friend with a lift at home who did them for me. To get at the fill bolt on the transfer case, you have to unbolt and lower the tail of the transmission enough to get at it because it's high up in the transmission tunnel. The drain bolt is removed easily.

 

There are a couple different write-ups, that explain ways to drain the transfer case without loosening or unbolting anything. I used a 120XP Gearset ratchet wrench and slit the floor pan insulation around the fill plug and was able to drain and fill the transfer case fluid. At 56K miles, the fluid was mostly black and needed changing. I also added some Lubeguard anti-shudder additive for transmissions, and it cured my front end scrubbing (binding) on tight turns.

 

Your car must have had more room. There was no way, even with the insulation pulled back, that I was getting a tool in there. But all I had to do is, while having the car on jackstands, keep the transmission held up with a jack, unbolt the 2 bolts on the transmission crossmember on one end and really loosen them on the other, then I was able to lower the transmission down like 2 inches which gave me all sorts of room to get my tool in there. I left the 2 bolts really loose just so it wouldn't be a pain to get them back in. It was very simple to do so no one should waste much time trying to get a tool to fit in there. I used a serpentine belt tool that is designed for tight spaces.

 

Perhaps the difference between the coupe and the sedan?

 

My "lift" was 4 12 ton jack stands holding the car 6" off the ground... lol
Did front, rear differentials and the TC all at same time. Was easy peasy. I removed the inner fender on the passenger side to get easier access to the fill tube on the front diff though. Would have been unnecissary on a lift.