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Hi, have a question regarding fluids draining, I saw a video on YouTube where some guy was swapping his manual gearbox from C7 Z51 to automatic from Z06 . He claimed that there is a specific procedure/tools to purge air from edif/elsd module, I mean if I've removed diff and trans and disconnected all the lines, I cannot just connect them back in the same way I have disconnected them when I will assemble it back? Do I really need to purge air from somewhere?
Thanks
Hi again and f**k me , I hoped to hear another answer , what do you suggest to do now? How to do it correctly ? To purge air from the modules or from the lines ? To purge air after I connect everything or before? Hopefully you can advise or maybe have some links to the manual
Hi again and f**k me , I hoped to hear another answer , what do you suggest to do now? How to do it correctly ? To purge air from the modules or from the lines ? To purge air after I connect everything or before? Hopefully you can advise or maybe have some links to the manual
Here are the relevant pages from the Factory Service Manual:
You will need the special tool pipe connector that maybe you could make yourself. However, you will also need a scan tool that is equivalent to the GM MDI2 dealer service scanner that can provide the proper commands to perform the bleeding process.
Here are the relevant pages from the Factory Service Manual:
You will need the special tool pipe connector that maybe you could make yourself. However, you will also need a scan tool that is equivalent to the GM MDI2 dealer service scanner that can provide the proper commands to perform the bleeding process.
Hope these pages help.
Bill
Thanks Bill , I have found similar info in the forum right here , but still have some questions , for example
1. how to fill elsd with hydraulic fluid .
2. "Attach the DT-51381 pipe to the high pressure line" (this tool should be connected to the end of the line that comes from the diff?)
3. Fluid wont come out without that tool ?
4. Scan tool, do you have any idea if "foxwell 510elite" will work for this purpose ?
5. Do you think it will be safe to connect everything as is to drive the car to the nearest dealership to do it properly ? (the closest one unfortunately is about 500km away )
If I understand the procedure correct I need to :
> Raise the car
> connect everything except the line the hydraulic line that going from the diff to the elsd
> attach DT-51381 to the end of the line that coming from the diff
> NOW do I need to start the car ? or should I run the whole process with car turned off but the ignition ON in order to turn ON the bleed process from scan tool ?
> Once complete I need to remove DT-51381 and attache the line back to elsd ?
Question : What about the hydraulic fluid that was spilled and will be missing in the system some amount , how do I refill it and how much
Last edited by KirillG88; Sep 13, 2023 at 01:19 PM.
Thanks Bill , I have found similar info in the forum right here , but still have some questions , for example
1. how to fill elsd with hydraulic fluid .
2. "Attach the DT-51381 pipe to the high pressure line" (this tool should be connected to the end of the line that comes from the diff?)
3. Fluid wont come out without that tool ?
4. Scan tool, do you have any idea if "foxwell 510elite" will work for this purpose ?
5. Do you think it will be safe to connect everything as is to drive the car to the nearest dealership to do it properly ? (the closest one unfortunately is about 500km away )
If I understand the procedure correct I need to :
> Raise the car
> connect everything except the line the hydraulic line that going from the diff to the elsd
> attach DT-51381 to the end of the line that coming from the diff
> NOW do I need to start the car ? or should I run the whole process with car turned off but the ignition ON in order to turn ON the bleed process from scan tool ?
> Once complete I need to remove DT-51381 and attache the line back to elsd ?
Question : What about the hydraulic fluid that was spilled and will be missing in the system some amount , how do I refill it and how much
It's in the pages Bill has posted up above. It uses Dextron VI
So the tool is just the end of the high pressure hose with its hose barb to attatch to a drain hose?
Those tools are unobtainium.
Do you really need the tool or can you just fill the reservoir and do the bleed? Looks like the tool is just to verify ATF is pumping out. Would'nt the ATF just return to the reservoir if hose is not disconnected and bubbles will get removed?
I just found two of the complete hydraulic pressure hoses used on ebay for $105. It has two ends that if I cut off the hose it should be the same thing. New hoses are not available from GM and are over $400.
In Bill’s post #4, the second page 7-150, step #12 says “From the scan tool menu, select Rear Differential Clutch Control Module, then select Control Functions, then Rear Differential Hydraulic Line Fill”.
Is there a scan tool under $1,000, other than GDS2, which will do this function of turning on the pump? Maybe a certain model of Autel?
In Bill’s post #4, the second page 7-150, step #12 says “From the scan tool menu, select Rear Differential Clutch Control Module, then select Control Functions, then Rear Differential Hydraulic Line Fill”.
Is there a scan tool under $1,000, other than GDS2, which will do this function of turning on the pump? Maybe a certain model of Autel?
Dan
I just bought this. https://www.obdii.shop/goods.php?id=24
I had emailed them to ask if this tool will do the eLSD Bleed. An engineer responded say yes it supports that function but I would need to know how to correctly do it.
I just bought this. https://www.obdii.shop/goods.php?id=24
I had emailed them to ask if this tool will do the eLSD Bleed. An engineer responded say yes it supports that function but I would need to know how to correctly do it.
Shoot, that's not too bad of a price to have such a tool.
In Bill’s post #4, the second page 7-150, step #12 says “From the scan tool menu, select Rear Differential Clutch Control Module, then select Control Functions, then Rear Differential Hydraulic Line Fill”.
Is there a scan tool under $1,000, other than GDS2, which will do this function of turning on the pump? Maybe a certain model of Autel?
Dan
VCX Nano….about $150. It’s the hacked version of the GM tool. Been around for years.
It’s not the easiest thing in the world to get loaded onto a laptop, but it does work and does everything the GM tool does. Some menu shots from mine….
Looking at the one for a bit under $400, that’s a really good deal. If I’m reading it right, it comes with the needed laptop loaded with the software. Sure it’s low end but you have a dedicated machine you don’t have to worry about a Windows update or other software update screwing it up. Not to mention you don’t have the hassle of trying to load hacked software yourself
It's in the pages Bill has posted up above. It uses Dextron VI
Late to the party here, but I believe Dexron VI is for the clutch part of the eLSD not the Differential Oil part that you have referenced. I don't mean to nitpick, I just want to make sure whoever might visit these instructions at a later point (I just found them today) didn't put the wrong stuff in the wrong hole! I can imagine that might get expensive.
Last edited by lllest; Sep 9, 2025 at 02:13 PM.
Reason: Dexron IV -> Dexron VI mistype
Late to the party here, but I believe Dexron VI is for the clutch part of the eLSD not the Differential Oil part that you have referenced. I don't mean to nitpick, I just want to make sure whoever might visit these instructions at a later point (I just found them today) didn't put the wrong stuff in the wrong hole! I can imagine that might get expensive.
Look at the picture. What's it showing? It's showing the eLSD fill port right next to the where the drivers side axle goes into the diff. That's what the post I was responding to was asking about.
The other section of the document that I did not highlight is for the diff fluid....ie the 75W90 that drains and is filled from the back of the diff.
Fluids draining / elsd module air bleed question
and f**k me , I hoped to hear another answer 
, what do you suggest to do now? How to do it correctly ? To purge air from the modules or from the lines ? To purge air after I connect everything or before? Hopefully you can advise 
)
