Rear diff fluid change - ZR-1 Net Registry Forums

Aurora40 · 11-21-2005

It seems like the only way to drain this is to take the casing apart. I'm not sure I'm up for that. So what I'm thinking is to suction out as much fluid as I can with some plastic hose through the fill hole.

I was then planning on filling up with the 4 oz GM rear diff additive, and then Mobil 1 75w-90 gear oil.

Is this an ok thing to do? Is there a better way? Am I making another classic ZR-1 blunder? Thanks!

Patton · 11-21-2005

There should be a 13mm drain plug in the back. Just unscrew and get a coffee.

I dont know how accurate this is because I dont have a shop manual. However I just checked my Chilton repair manual and it says to use the 4floz. of GM limited slip additive part no. 1052358 and (doesnt say how much) SAE 80W-90 GL-5 gear lubircant. Sounds like that Mobil1 stuff would do just fine. BUT WAIT UNTILL SOMEBODY WITH A SHOP MANUAL CONFIRMS ALL OF THIS.

Hope this is some help! Good luck!

Aurora40 · 11-21-2005

I've a shop manual. I think the drain plug was only certain years? My manual doesn't show one in the schematic. Also, the capacity is like the tranny, you pour it in until it comes out the fill plug. So you can't overfill it.

I'll take a closer look, I'm not in a rush to do it, and see if there's a drain plug. But it doesn't seem like there is from the manual. Thanks!

blackjack · 11-21-2005

i use amsoil severe duty gear oil,75w90...amsoil says you dont need
the diff additive...my gm service manager says that most new cars
dont need the additive anymore,with the synt lube...they only brought it back by popular demand...cant say if it is true or not
blackjack
91 ,1735

Patton · 11-22-2005

Well, hell. It looks like you know what you are doing.
Go on now,... Git Er DUNN

ZR1 MK · 11-22-2005

No factory drain plug. You could install an aftermarket unit for easy fluid changes. I change my fluids more often because of track usage, so this mod is far more important to me than the average owner.

Tom · 11-22-2005

The 90 does not have a drain plug on the differential, but there is one on the transmission. I went to Autozone and bought a suction gun that looks similar to a grease gun. It can be used to suction out the old oil and then used to put in the new oil. I used the additive and Redline gear oil in the differential. The suction gun can also be used to refill the transmission and makes it a very easy job to refill the differential or the transmission.

Aurora40 · 11-22-2005

Hey Tom, I've got a suction gun just like you are talking about. The only problem with it is fluid will drip out the weep hole on the back. But other than that it's great. I am always skeptical of using it to fill stuff up, though, because I use it to suck out disgusto stuff. I guess I worry about it contaminating the new stuff. Hopefully the tall narrow bottles that gear oil comes in will be narrow enough to pour right in the diff. But if not, I'll do what I did with the tranny and use a long length of hose that runs out to the side of the car, and pour it into the hose.

Thanks for all the replies! Glad I wasn't over or underthinking this one!

Tom · 11-22-2005

I've never had a problem with mine dripping out the back, I guess mine just seals better around the plunger. It has been a while since I have used mine so I don't remember if it comes apart easily like a grease gun so you can disassemble it and clean it out, but you could flush and clean it using clean oil or a solvent that evaporates readily.

11-27-2005

I have had great success to use this hand pump from MityVac:

http://www.northerntool.com/webapp/w...74&R=200008074

I think I bought mine from Sears, but they sell them at a lot of the auto parts stores. It is very reliable and easy to clean out. I use it to drain the differential and replace the gear lube with the opposite flow.

Craig

11-21-2005	#1
Aurora40 Join Date: May 2005 Location: Leesburg, VA Posts: 2,704	Rear diff fluid change It seems like the only way to drain this is to take the casing apart. I'm not sure I'm up for that. So what I'm thinking is to suction out as much fluid as I can with some plastic hose through the fill hole. I was then planning on filling up with the 4 oz GM rear diff additive, and then Mobil 1 75w-90 gear oil. Is this an ok thing to do? Is there a better way? Am I making another classic ZR-1 blunder? Thanks!

11-21-2005	#2
Patton Join Date: Dec 2003 Location: Sacramento, CA Posts: 220	Re: Rear diff fluid change There should be a 13mm drain plug in the back. Just unscrew and get a coffee. I dont know how accurate this is because I dont have a shop manual. However I just checked my Chilton repair manual and it says to use the 4floz. of GM limited slip additive part no. 1052358 and (doesnt say how much) SAE 80W-90 GL-5 gear lubircant. Sounds like that Mobil1 stuff would do just fine. BUT WAIT UNTILL SOMEBODY WITH A SHOP MANUAL CONFIRMS ALL OF THIS. Hope this is some help! Good luck! Last edited by Patton; 11-21-2005 at 07:12 PM.

11-21-2005	#3
Aurora40 Join Date: May 2005 Location: Leesburg, VA Posts: 2,704	Re: Rear diff fluid change I've a shop manual. I think the drain plug was only certain years? My manual doesn't show one in the schematic. Also, the capacity is like the tranny, you pour it in until it comes out the fill plug. So you can't overfill it. I'll take a closer look, I'm not in a rush to do it, and see if there's a drain plug. But it doesn't seem like there is from the manual. Thanks!

11-21-2005	#4
blackjack Join Date: Aug 2005 Location: north of montreal Posts: 510	Re: Rear diff fluid change i use amsoil severe duty gear oil,75w90...amsoil says you dont need the diff additive...my gm service manager says that most new cars dont need the additive anymore,with the synt lube...they only brought it back by popular demand...cant say if it is true or not blackjack 91 ,1735

11-22-2005	#5
Patton Join Date: Dec 2003 Location: Sacramento, CA Posts: 220	Re: Rear diff fluid change Well, hell. It looks like you know what you are doing. Go on now,... Git Er DUNN

11-22-2005	#6
ZR1 MK Join Date: Aug 2005 Location: NY Posts: 142	Re: Rear diff fluid change No factory drain plug. You could install an aftermarket unit for easy fluid changes. I change my fluids more often because of track usage, so this mod is far more important to me than the average owner.

11-22-2005	#7
Tom Join Date: Jan 2004 Location: Southern CA Posts: 108	Re: Rear diff fluid change The 90 does not have a drain plug on the differential, but there is one on the transmission. I went to Autozone and bought a suction gun that looks similar to a grease gun. It can be used to suction out the old oil and then used to put in the new oil. I used the additive and Redline gear oil in the differential. The suction gun can also be used to refill the transmission and makes it a very easy job to refill the differential or the transmission.

11-22-2005	#8
Aurora40 Join Date: May 2005 Location: Leesburg, VA Posts: 2,704	Re: Rear diff fluid change Hey Tom, I've got a suction gun just like you are talking about. The only problem with it is fluid will drip out the weep hole on the back. But other than that it's great. I am always skeptical of using it to fill stuff up, though, because I use it to suck out disgusto stuff. I guess I worry about it contaminating the new stuff. Hopefully the tall narrow bottles that gear oil comes in will be narrow enough to pour right in the diff. But if not, I'll do what I did with the tranny and use a long length of hose that runs out to the side of the car, and pour it into the hose. Thanks for all the replies! Glad I wasn't over or underthinking this one!

11-22-2005	#9
Tom Join Date: Jan 2004 Location: Southern CA Posts: 108	Re: Rear diff fluid change I've never had a problem with mine dripping out the back, I guess mine just seals better around the plunger. It has been a while since I have used mine so I don't remember if it comes apart easily like a grease gun so you can disassemble it and clean it out, but you could flush and clean it using clean oil or a solvent that evaporates readily.

11-27-2005	#10
HAWAIIZR-1 Guest Posts: n/a	Re: Rear diff fluid change I have had great success to use this hand pump from MityVac: http://www.northerntool.com/webapp/w...74&R=200008074 I think I bought mine from Sears, but they sell them at a lot of the auto parts stores. It is very reliable and easy to clean out. I use it to drain the differential and replace the gear lube with the opposite flow. Craig