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Are the rear diff mounts oil filled? Time for an update!
I’m assuming you’re joking about the mounts being filled with oil lol
Its funny you posted, I was literally going to post updates yesterday and I forgot.
Ok, buckle up, we’re going for a ride!
So in my last post, I got the diff out of the car, and had a drivetrain sound I couldn’t figure out. I then pulled the trans and torque tube and (leaving the bell housing and clutch in the car) and started the engine and the sound was gone. Ok, great, we’re getting somewhere. So I put the torque tube back in the car along with the X-pipe and started the engine again, still no sound. Great, this is getting better! I put the trans back in the car and started it up, sound returned but was much more faint. So I figure, well maybe something was misaligned. Oh well, it should be good now. So I decided fo focus on the diff rebuild at this point since that was the next logical step.
With the diff out, I opened the side of the case up and took out the carrier. Upon removal, I found that the inner carrier bearing race was totally destroyed!!! This is nuts because it wasn’t making any crazy sounds!
So, I had to replace the bearing. But wait, it gets better! The bearing is not available from GM. You read that right! Unavailable. Just like the spider gears when we tried to get those in the past. Then, as I was taking the diff carrier apart to install my new 4 pinion setup, I found that one of MY spider gears was already cracked.
So at this point I’m going to have to buy ANOTHER diff for parts, on top of the diff carrier and misc parts I already bought for the four pinion setup already.
Enter Dave01GT. Dave cut me a great deal on a spare diff he had. (Thanks Dave!)
so after the part diff arrived I started disassembly. That did was from an A8 and I have an M7 so I couldn’t just swap my diff completely. I also had to swap the bearings over from that case to mine since my shims were already pretty close and my pinion was already set correctly. So I worked with a friend of mine who drives a super fast turbo mustang, (and we won’t give him crap about it being a mustang since he helped me out a lot) and we got the bearing race swapped over and the bearings off the carrier swapped to the new custom drilled carrier assembly. Be forewarned, in order to get the inner bearing race out we had to heat the surrounding area to 250* and then still had a fun time with a hammer and chisel to get it out. Theres actually a small secret hole on the other side of the case that you can use to drive the race out with a proper punch. After that I removed the pinion assembly and cleaned my case out real good since my bearing had failed there were small pieces everywhere.
Ok so I hosed out the case with water and then brake cleaner to get it all nice and pretty. We got the new bearing race installed, and I then started on building the carrier. I figured that since my car had 55K miles on it I was best suited to replace the clutch packs in the diff so I used the ones from my parts diff which were about 0.002” thicker for each of them giving me a much newer set. Yay! Also got my new RPM Transmission’s 300m treated stub shafts installed!
I worked to then get everything for the carrier assembly fully assembled properly, and torqued properly. When it came to the ring gear bolts those need red loctite and had to he torqued to 107 FT LB. Good luck holding that thing in a vice and torquing it to that spec without damaging something! So I decided for this I was going to use the air impact, along with some torque limiting extensions I had and torqued them to 110 LB FT. (It’ll be just fine )
And theres a couple pics where you can see the custom pin and second set of holes that had to be drilled in the carrier. Thanks to Albert (Rflow) for his help with that!
got everything installed, and checked ring gear backlash, and everything looks good!
More coming in a sec, don’t wanna lose all this writing lol
Heres a couple before and after of the stock axles vs my new DSS axles:
And so I got the diff back in, filled it with fluid, and reinstalled the rear cradle and started her back up. Guess what! The clank sound came back!! I reached out to Mantic about it as I believed it to be related to the clutch and they advised that since the flywheel is lighter and my car was idling soo low it was the lash between the trans gears I was hearing slopping around. They recommended I get the idle fixed and the sound should minimalize, but ultimately is normal due to the lighter flywheel that does not dampen the engine oscillation in conjunction with the transmission.
So, I took her for a spin to get some gas, even though shes running a little rough.
Current status is that I am working with fellow CF friend Higgs Boson to get my base tune done and he’s been such a help throughout all of my builds whenever I need him. (Thanks again man!)
I’ve been driving the car to work and back for a couple days now logging data and we are tweaking the tune to get it more stable so I can srive the car to Texas for LMR to tune the car on spring break. Speaking of which I need to call them and setup an appointment
So, VERY soon I will have dyno numbers and videos to share!!
Let me know when you go to LMR as I plan to stop by there and Vararam in in that area too. Would be fun to meet up and see your slow car. lol
I wasn't excessively sober when I tried to make a joke about making sure you filled your diff mounts with oil but I guess you kinda got it anyway. lol Glad you have it back on the road. Do you have confidence that your clutch noise will subside with a tune?
Let me know when you go to LMR as I plan to stop by there and Vararam in in that area too. Would be fun to meet up and see your slow car. lol
I wasn't excessively sober when I tried to make a joke about making sure you filled your diff mounts with oil but I guess you kinda got it anyway. lol Glad you have it back on the road. Do you have confidence that your clutch noise will subside with a tune?
probably will be Wednesday 3/6. I’m not sure on the sound 100%, but the car is running ok it seems. 250 miles on the new motor breaking it in currently.
I’ve been driving it to work for the last week just trying to put some break in miles on her. The last thing I want is to break down on my way to Texas! So far I’ve made it to 560 miles on the engine. Last night I drained the oil and things look excellent.
Below is a pic of two paper towels, the left being what I wiped off my magnetic drain plug, and the right being some of the actual oil. The great news is there was overall very little that came off the magnet which is good news and means the engine is breaking in and nothing appears wrong at this point. The oil was still fairly golden and transparent as you can see on the right paper towel.
Last night I also started putting the blower on. This was intentionally left off because I didn’t want the break in oil and any possible particles making their way theough the blower. So last night I got the intercooler installed, all piping, the head unit and all oil lines, and the BOV.
I still need to fill the engine oil, put on the blower belt and clamp down the charge pipe to the throttle body, check everything for leaks, and put on the filter/intake tube. I also installed my new 8 rib 3.00” griptech upper pulley on the headunit last night (I’m running 8.25” lower) as well as my new DSX IAT and Baro breakout cable.
02-19-2019, 08:29 PM
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