Member
hello all
Wanted to post an issue that im currently having with my E36 rear differential. to bring everyone up to speed I have swapped a Chevrolet V8 into my Volkswagen Passat wagon, and incorporated an E36 rear differential because my VW rear end has reverse cut gearing.
This past weekend we had our first test ride and these are the symptoms im running into currently. At first takeoff the car shifted into second gear, when doing so the car seemed to slow quickly as if the ebrake was pulled or my foot was on the brake.. that slowly went away and I didn't notice it again. then, under a semi hard take off (maybe 30% throttle) the car came completely out of gear. while sitting still and the car in gear, the driveshaft was spinning, but the car wasn't moving. I could visually see the driveshaft spinning the pinion shaft into the rear end, but the axles were not moving. after towing the car back into the garage I jacked up one side of the vehicle at a time, got it on the stands, and miraculously the car seemed to be normal again, wheels were locked in, turning when the driveshaft was turning. weird. went back on the street and took off, and boom car just rolled to a stop like it was in neutral again.
my question is, are the ring and pinion separated and not making contact? could I have possibly chewed the pinion gear teeth off? and if I did, how did it temporarily fix itself? I'll get the diff torn out and open the cover to inspect here in the next 48 hours but I just thought that was really bizarre. specs on the diff below.
E36 small case diff
open differential
welded spider gears
everything appeared to be alright before installation, cleaned and changed the fluid etc etc. anyone encountered this problem? it has to be something to do with the pinion bearing not making contact with the ring gear, however it made no horrendous noises, chewing of any gears while driving.
I am under the assumption this rear diff is good for about 250-300hp, and im running well over that, but I ended up purchasing this diff locally to keep fabrication processes moving forward, then id go back and purchase the correct diff that can handle the power etc etc.
any help or input would be greatly appreciated.
Member
no one?
I'm lost
I would imagine something is worn/broken to the point where it'll work under no load (wheels in the air), but breaks free while under load.
Member
yeah that's what is so bizarre.. literally after I put it in the air it started working fine.. I took the jack stands out and put it back down on the ground, and literally did a burnout right in the garage.. i'll get the diff down and out tonight so there will be hopefully a definitive "oh wow" moment when I drain the fluid, but I just thought it was so weird that the problem temporarily fixed itself. a driveline shop said I could have stripped the teeth off the pinion gear, and when I dragged it home in reverse it sort of " re teethed" the gear temporarily, also sounds bizarre to me. oh well. i'll update tonight once I get it opened up.
Member
axle shortage.jpg
diff flanges.jpg
found my problem. when doing the rear end swap on my car I was measuring the length for the custom shafts when the suspension was all the way down. I got mixed up thinking that I need the suspension down because that's going to be the longest point of travel with the shafts. well that was correct, but unfortunately when I got the car jacked up on stands, and then jacked up the tires in order to get actual ride height, the axles pulled away from the rear diff, thus pulling the flanges past the circlip and eventually slipping the flange spline out of the spider gear. dang, but at least I know whats going on now.
Member
Can you easily get another set of axle drive cups? Are you just planning on swapping in a whole new diff? I have some spare cups from a small case E36 diff here that I don't want a ton of cash for, but I know shipping to Aus will be dear.
Member
ive actually moved home since the last time ive posted on this forum. I live in Grand Rapids, MI.Originally Posted by jakermac
I'm not exactly sure what I'm going to do just yet. obviously I need to get the correct axle shafts made which isn't a problem. Only reason I have a small case diff in the car right now is because I needed to keep this project moving forward and it was local. my plans are to eventually get that out once I've put 200 or so miles on the car for the initial break in, and swap in an LSD Medium case diff.
currently I can get the cups back into place and locked in with the circlips, so I might lengthen the axles first, go for test ride number 2, and see where im at from there.
I'm lost
Welcome back to Michigan!
Member
Thanks!
Member
Well if you decide to try another pair of cups, I'll send you some for $40 shipped.
Member
thanks man ill definitely keep that in mind. from what I believe ive read, you can interchange the smaller cups into the M3 rear end? are their any differences? I have found a 3.23 M3 medium diff from a 98' locally for 350 bucks, but the custom shafts we made for initial mockup are the smaller diameter flange pattern. so my question is, will the small case diff flanges just slide right into the medium case LSD diff?
thanks guys.
Member
Pretty sure the answer is yes, but I can confirm when I get home tonight (if I don't forget). I have both on the shelf. But the diff housing/case is wider so the custom shafts might be too long.
Member
Though the diameter and splines are the same, there are some significant differences in the stubs. The surface for the oil seal is a smaller diameter on the 6cyl (medium case diff) stubs and the seal guards/shields are very different.
Member
thank you for the heads up on that I appreciate it! was a glorious day yesterday, we removed the axle shafts, lengthened them to the dimension we needed to get things to start working again, went out for some test drives and we are back in business! super happy about getting on the road for some test and tuning. sounds like I will need to upgrade the shafts once again when I get into a medium case diff, which isn't too big of a deal. thanks again for all your help and info!
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a couple videos for viewing pleasure.
https://youtu.be/Z0OPs0P5Jag
https://youtu.be/-R9K7WRxNpo
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