Differential gear fitment issues

[theunz]

It seems that everything I’ve ever read about swapping ring and pinion’s has just gone out the window! Time and time again I have read that the 4:37, 4:62, and 5:12 ratios require a 4mm spacer while the rest do not. I just came back from the shop that is swapping my 4:62 to my NOS 4:11s. My 4:62’s did not have the spacer and fit just fine with only a few thousandths of shims. The 4:11s with no spacer (which it’s not suppose to need) is a few thousandths too wide to even fit in the carrier. He says it’s so close that he probably could tap it on in but it would just bind up and not turn. He says he needs about 25 thousandths more clearance to be able to properly shim it to set backlash. So, I wondering if everything goes out the window when you install the LSD in place of the open differential? By the way it is the factory LSD. Looks like the only solution is to machine the case for more clearance.

[david premo]

So Mike,
That’s what is what has happened to me recently with a customer diff, it has to do with the housing, gears and spools that are at or past the limit of range. I have been trying to do the same thing for someone else I’m now seeing if the third differential will work, third time is a charm I hope. I also know someone else who has had the exact same problem, they took a brand new set of 4:11 gears to a shop and they can not get a good pattern. The second differential I worked was actually too worn to get a confident pattern so I stopped and picked up the third one that I am about to give a go.
Dave

[theunz]

They say misery loves company, sorry it has to be you Dave. It is interesting however to find out I’m not alone in this debacle. What’s most baffling is the fact that my 4:62 gears work without the spacer! I too tried another case, but it was within a couple of thousandths of the first one. Hopefully I can get the case machined next week and report back on the results.

[spyder]

There is a posi center section which has the 4mm built into it so the 4.375, 4.625, 5.125 ratios don't need the spacer. Sounds like your 4.62 is one and will only fit these ratios. It's the one on the right.



For the record, my installed posi is a 3.70 that was originally a non posi. Changed it last year from a 4.88 posi that also was installed into a non posi pumpkin. 4.88 was fun but I got tired of 4k rpm at 65mph

It's been posted before, to lazy to search...
https://web.archive.org/web/20050209204 ... 0/lsd5.asp

[theunz]

Thank you Spyder! I had previously looked at the chart that you linked to and interpreted it to mean two different housings for the 3rd member not a different cap for the LSD. I think this is exactly my issue as it looks like my cap is the thicker one. I don’t have the unit with me but here is a picture that sure looks like the thicker one you posted. You are a true asset to the community