I got the rusty GSL rearend with the cables and brackets still attached. It has the rear disks and the LSD. The donor had 178,000 miles on it.

I'll pressure wash, then wire brush until it's ready for oxide primer and black epoxy enamel, but then...

The local Mazda dealer won't touch it. "There's nobody here familiar with those old cars". But, this is not a rotary part. It's a frickin rear end, for Chrissakes !!!

But, they do have the bearings and seals and such available. I hope I can leave the chunk alone... maybe just inspect it and clean it and refill with LSD gear lube.

My questions:

Should I leave the chunk alone and hope it's in good shape ? or should I get a shop to freshen it up ?

I have the stock 3.9 pinion gear, so maybe change out the ring and pinion to a 4.8 since I have taller tires than stock ???

Anybody got a ring and pinion in great shape for a reasonable price that's taller than 4.11 ???

Is this a DIY job to rebuild everything except the third member ( chunk ) ? or should I get all the parts and let a local performance shop do it ?

I would appreciate any insight and/or experiences to help me muddle through my own decision making process.

 

PITA to re-build and realy not cost effective. Rearends go for around $100 here, parts to make a 3:90 into a 4:076 or 4:11 is around $700. Take the 3rd member out and inspect the teeth for wear and blueing. If there is any blueing it has been run low of fluid, or run out of fluid. Check for play, turn it and see the teeth mesh well. Then re-seal, providing it is good, let set then fill.

 

You might need a machine shop to press the bearings on the axle shafts, but aside from that, unless the Donor whined, you should be good.

If you're replacing the ring and pinion, you will need a little spacer that goes on the pinion... It's available in 4 of 5 thicknesses each varying by about a quarter of a millimeter... I'm not sure how to determine the correct thickness you need.

There's several ring and pinions available, some from your local junkyard.

Being that Miatas have compatible gear sets, reuse this list:
http://members.aol.com/solomiata/Drivetrain.html

If you have an 84/85 rear end, you can also use the Torsen Differential from a Miata. If not, just the gearset.

 

Brian,

You need to change your avatar ... so I can read your post from beginning to end without stopping.

 

LMAO! I change it once a week, but I don't think that the one I have for next week will help you any.

 

So I start a thread on rearends and your avatar shows up !!!

If I start a thread on headlights, I guess Dinner will post there, too. You guys need to stop all that !

 

I just took my se rear out and replaced it with one that had about 90thousand miles. The only issue it has is some bearing noise that is coming from the outer axle bearings. My old rear end made all kinds of noises even though I had put about 40 thousand miles on it with synthetic gear lube in it. Btw that rear end had about 175k on it. The easiest way to tell the condition of the third member is to try to spin the imput yoke (the one that driveshaft attaches to) while holding one of the axles. First of all, you should not be able to turn the yoke while holding one of the axles. If you can, that is a good indication that the LSD is going out. Second, there should not be more than a quarter inch of play at the yoke when holding an axle from moving. If there is, that is a pretty good indication that the ring and pinion has an unacceptable amount of lash in it. This would necessitate a new ring and pinion and therefore a complete rebuild. If none of these issues are present, I would remove the third member and of course axles, thoroughly clean the axle housing and reinstall everything with new gaskets and fresh gear lube.