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I have come into possession of a complete Corvette rear differential/suspension. I was told it was from an early C4 but I'd like to confirm. I've found a site that cross references diff numbers to years and types, but I can't find a comparable 6-digit number on my diff. Where should I be looking?
Unfortunately, that is the web site I had found that provides the number cross references. But it doesn't say where to find the number on the diff. That's what I need now. ... But thanks for trying.
I have come into possession of a complete Corvette rear differential/suspension. I was told it was from an early C4 but I'd like to confirm. I've found a site that cross references diff numbers to years and types, but I can't find a comparable 6-digit number on my diff. Where should I be looking?
What is all of the information you have?
The information if it's on the differential would be on the bottom of the housing itself. There would be likely a line with a six digit number, a GM assembly number, a production date and a line with the ratio.
It is NOT on all rears.
There's either 3 bolts or 2bolts across the top of the rear cover attaching it to the rear differential, that will do some basic identifying and it's likely the more important information for the moment.
You should be able to tell if it's got a caliper actuated disc e-brake or if it's got a cable into a backing plate which would indicate a shoe in rotor e-brake. Shoe in rotor is '87 or earlier, caliper actuated disc is '88 or newer.
You can remove the cover and there will be enough information on the ring gear to identify everything that you should be interested in.
If you can turn the half-shafts do one complete turn of the half-shaft and count the rotations of the pinion flange. You can approximate quite accurately the ratio from that count.
One turn of the half-shaft should produce 2 1/2 turns, 2 3/4 turns, 3+ very little, 3 1/3, 3 and less than 1/2 or 3 1/2+ very little.
I found the number 42861 stamped into the diff, and the number NYU003424 is on the spring. Turning the wheel I determined it is likely at 3.07 gear ratio. That's about it. I could post a photo if that would be definitive.
I found the number 42861 stamped into the diff, and the number NYU003424 is on the spring. Turning the wheel I determined it is likely at 3.07 gear ratio. That's about it. I could post a photo if that would be definitive.
3 bolts across the top or 2? Which e-brake? Post the snapshots that you might have.
The bottom of the housing is the one spot I could not clearly see (because its resting on a jack). I'll look again later and check out the other indicators you mentioned.
The bottom of the housing is the one spot I could not clearly see (because its resting on a jack). I'll look again later and check out the other indicators you mentioned.
NYU doesn't help - that spring code is used with both style of rears. If you have a box end wrench that fits the pinion nut - what size is that wrench?
OK, here's what it looks like from the back side of the diff:
There are two numbers cast into the batwing: 14105119 and 43164. There are no markings on the bottom of the diff case.
You've got a D36 rear and you mention the 3.07 from axle/pinion rotation and the NYU confirms it's NOT from an '84 or an '85 so if the information isn't on the underside of the housing you need to confirm the e-brake to ID the rear as it sits. Is there a blue paint stripe on the cover bushings?
The casting information on the cover "hints" at an '88+ cover and the e-brake should be caliper actuated by cable pad to rotor.
Here's a photo of the caliper mount. The number on the mount indicates it is from an 88-96 model. No blue paint.
I also obtained front suspension pieces from the same source, although they may or may not have been from the same car. I've identified them as coming from an 88-90 model. So based on all we have so far, I think its reasonable to conclude this rear end came from an 88-90 model.
Thanks for your help in this.
Last edited by kellsdad; Apr 30, 2015 at 11:47 AM.
How to identify a C4 differential
