Rear Diff Fluid

[MatthewAMEL]

Yeah, pretty typical but a lot of enthusiasts like to change out the fluid to to keep it nice in clean as the clutch material sludge builds up in there. It is easy to do but the fluid is pricey.

The clutches aren’t exposed to the diff fluid.

There is a procedure for servicing the eDiff clutch pack, but you have to open the diff to do it. There is no interval for the diff clutches. Just the fluid in the pumpkin itself.

 

[dribs15]

Must be made of liquid gold.

 

[raptor5244]

The clutches aren’t exposed to the diff fluid.

There is a procedure for servicing the eDiff clutch pack, but you have to open the diff to do it. There is no interval for the diff clutches. Just the fluid in the pumpkin itself.

When I changed the E-diff fluid on my ZL1 after 1500 miles this is was the magnetic drain plug looked like. I was told this silver sludge is the clutch pack material that gets picked up. Did you notice anything similar on the 4BW drain plug when you drained and replaced the fluid?

 

[Mcard23]

When I changed the E-diff fluid on my ZL1 after 1500 miles this is was the magnetic drain plug looked like. I was told this silver sludge is the clutch pack material that gets picked up. Did you notice anything similar on the 4BW drain plug when you drained and replaced the fluid?

View attachment 18980

My 1LE looked the same way, the blackwing was pretty clean all 3 times I’ve changed it.

 

[sleepys4]

lot of varying information here. In summation both the CT4 and CT5 Blackwings use the same 19418501.

This should be helpful to anyone searching.

Also my dealer told me my diff fluid was 19368514 which I knew was incorrect seeing that is the fluid for the open diffs. So if you can most of the time its better to do the work yourself. Most of these guys don't have a clue smh.

 

[Head Hunter]

When I changed the E-diff fluid on my ZL1 after 1500 miles this is was the magnetic drain plug looked like. I was told this silver sludge is the clutch pack material that gets picked up. Did you notice anything similar on the 4BW drain plug when you drained and replaced the fluid?

View attachment 18980

I replaced the stick gears on my diesel with Yukon 4.56 to accommodate for the bigger tires I was running and when I changed the diff fluid after break in, that’s about what I found. Pretty normal for new gears to lose some material during break-in

 

[thefleshrocket]

I ordered 19418501 from here: 19418501 GM 75w-85 SAF-EH Modified Low Viscosity Rear Axle Lubricant - 1 qt | GM Parts Store

$35.80 per quart, $11.53 shipping, and no tax. $83.13 total.

 

[rubberduck]

I ordered 19418501 from here: 19418501 GM 75w-85 SAF-EH Modified Low Viscosity Rear Axle Lubricant - 1 qt | GM Parts Store

$35.80 per quart, $11.53 shipping, and no tax. $83.13 total.

That's a good find. Have they actually shipped them? I kept running into minimum quantity issues with online suppliers.

 

[PrimeTime]

gmpartsdirect.com​

Took a minute to get the order sent, yes it was fulfilled. Shipping gets a chunk of it, $$$.

​

Processed items​

Item	Part #	Quantity	Amount	Status	Tracking Number	Ship Date
75w-85 SAF-EH Modified Low Viscosity Rear Axle Lubricant - 1 qt	19418501	3	$97.59	-	Jun 06, 2023

Subtotal
$97.59
Shipping (Economy)
$19.19
Total
$116.78

Communication​

 

[Head Hunter]

19418501 is the GL-5 that is referenced above. The rear ends may not be the exact same in both cars, but the main point to consider is the material that the diff clutch packs use. That material needs a very specific lubricant in order to work as designed. I had a SS sedan at one time, and everyone just assumed it used a Camaro drive train, which is mostly true. However, it used different clutch packs and those that put in the LS oil experienced basically an open differential since the friction was not right. I wouldn't go assuming on the diff fluid with these cars.

I called my local Chevy dealership which is an hour closer than the Caddy dealership and they gave me the part number for the wrong fluid (the non eLSD from the service manual @poor-sha posted above your post.). Thankfully I double checked this thread and found that post and got the right fluid.

 

[thefleshrocket]

That's a good find. Have they actually shipped them? I kept running into minimum quantity issues with online suppliers.

It took them a week or two to get it shipped, but it showed up last week.

 

[thefleshrocket]

I've got about 1600 miles on my 5BW and am going to do a track day in the next month or so. I can't find anything in the manual about differential fluid changes when tracking the car but seem to remember that it should be changed either before or after the first track day. Which is it?

Nevermind, found this very handy PDF. https://www.cadillacvnet.com/forums...-performance-supplement-unofficial-pdf.15878/ It says to change at 1500 miles prior to first track event.

 

[Carguyshu]

I've got about 1600 miles on my 5BW and am going to do a track day in the next month or so. I can't find anything in the manual about differential fluid changes when tracking the car but seem to remember that it should be changed either before or after the first track day. Which is it?

Nevermind, found this very handy PDF. https://www.cadillacvnet.com/forums...-performance-supplement-unofficial-pdf.15878/ It says to change at 1500 miles prior to first track event.

The owners manual actually says do it AFTER the first track day.

 

[Head Hunter]

The owners manual actually says do it AFTER the first track day.

Owners manual for a CT5-V Blackwing says to do it both, before and after. (after 1500mi and before first track event, then again after first racing or competitive driving event and after every 24hrs of competitive driving.)

 

[thefleshrocket]

So is anyone changing their 5BW's diff fluid both before AND after their first track day? My gut feeling is that one or the other is necessary--what does the ZL1 manual say to do?

 

[Head Hunter]

So is anyone changing their 5BW's diff fluid both before AND after their first track day? My gut feeling is that one or the other is necessary--what does the ZL1 manual say to do?

I'm absolutely changing it before - I've done new gears on my lifted truck and on my race cars of past and always did fresh fluid after 500-1000 miles, and the crap that I find coming out from the gears finding their mating point is pretty ugly. I'm not 100% sold on doing it again AFTER I get back from the track, but for $100 and 20 minutes of my time, I'll probably do it just for the sense of peace and knowledge it was done incase of any potential issues in the future.

 

[rubberduck]

I did mine at 1600 miles and the fluid looked great. I ran a magnet through it and came up with zero. Probably wasn't necessary in my case.

 

[poor-sha]

So is anyone changing their 5BW's diff fluid both before AND after their first track day? My gut feeling is that one or the other is necessary--what does the ZL1 manual say to do?

Yes, I did both. I am also the guy that didn’t do my first oil change until the oil life monitor said to. Follow the manual and no warranty issues with track use.

 

[MatthewAMEL]

So is anyone changing their 5BW's diff fluid both before AND after their first track day? My gut feeling is that one or the other is necessary--what does the ZL1 manual say to do?

Yes. I did it that way in the BW, my 1LE and the C6 before.

The Camaro manual says to change after 1,500 break-in miles, before 1st track day. Then based on hours after.

 

[MookdocOE]

Yes, I did both. I am also the guy that didn’t do my first oil change until the oil life monitor said to. Follow the manual and no warranty issues with track use.

Really? That is something I couldn't do because I know what kind of crap is in there. I just did my factory fill at 1k miles and major bearing breaking in oil glitters with lots of iron mud caked on everything.