1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Differential replacement

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Old 05-31-07, 09:42 AM
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Differential replacement

Hi, I have an '83 Rx-7, it might be the GSL (? - I bought the car without any emblems) it has 4 wheel disks but not the limited slip differential. I just blew the diff. in a freak accident - showing off and now I need to replace it. I found an '85 non-GSL (drum brakes) at a local wrecker's.
so here's my question; because the differential gears separate from the axle assembly as a unit - rather than there being a conventional diff. cover that can be removed to gain access to the internals, how can I remove the axle shafts enough to disengage the differential gears and remove the unit? (normally you'd remove the cover and then pull out the retaining pins right?)

Thanks for any help.
Mr. Showoff.
Old 05-31-07, 09:54 AM
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4 Wheels Disks means it has a Limited slip, just not working correct.

to pull the diff you have to remove the brakes and pull both axles out.

The cars had two sizes of Axles, 79 - 83 and 1/2 had Small axles and 84 -85 had large axles, so an 85 diff may not work for you.

Your choice is to find a diff that will work, repair yours, swap out the entire rear end for the Drum one.
Old 05-31-07, 09:56 AM
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Where is edmonton in CALI.
Old 05-31-07, 11:15 AM
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Old 05-31-07, 11:22 AM
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as stated above, swapping in a diff from a drum brake rear end will not solve anything. you'll need to get a disc brake diff from 81-83 as Hades12 stated. once you get the brakes off, you'll most likely need a puller to get the axles out. after that, remove the driveshaft, the yolk on the diff, drain the diff oil, and finally remove the differential itself.
Old 05-31-07, 11:32 AM
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You can just swap the 3rd member.
Old 05-31-07, 11:25 PM
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Originally Posted by wackyracer
You can just swap the 3rd member.
I realize this could be a joke (member, he he) but it sounds so simple, please clarify :P
Old 05-31-07, 11:59 PM
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Originally Posted by Hades12
4 Wheels Disks means it has a Limited slip, just not working correct.

to pull the diff you have to remove the brakes and pull both axles out.

The cars had two sizes of Axles, 79 - 83 and 1/2 had Small axles and 84 -85 had large axles, so an 85 diff may not work for you.

Your choice is to find a diff that will work, repair yours, swap out the entire rear end for the Drum one.
you say the old axles were '79 - '83-and-a-half? does that mean that mid '83 changed to the bigger axles - and that there's a chance mine could have the bigger axles already? cause that would be lucky. My car's not here right now or else I run outside and check the manufacture date.
Old 06-01-07, 12:39 AM
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Originally Posted by anotherfire
I realize this could be a joke (member, he he) but it sounds so simple, please clarify :P
Its not a joke. I've done it many times. In fact, I use 81-82 GSL 3rd members on both of my RX-3's with KIA gears.

Im not sure if you have a small or large axles. Say you have the large axles, unbolt the brake drum assembly from the axle flange. Take the axles out using (1) a puller or (2) install the spare tire but dont tighten the lug bolts - either bang on tire with a rubber mallet OR yank on it to get the axle out. No need to take the entire assembly out but just a few inches off the axle flange. Unbolt the orig diffy and install the GSL 3rd member.
Old 06-01-07, 04:20 AM
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If the driveshaft bolts to the diff flange with nuts and bolts, it's most likely a large axle diff. If it's bolts only and no nuts, small axles. Yes, it's easiest to simply swap the 'member', make whatever you want of the designation, lol.

If you tore up the ring/pinion gears, you can replace it with most any other one, iirc. If you don't know how to rebuild a diff, have it done by a pro.
Old 06-01-07, 09:46 AM
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Originally Posted by trochoid
If the driveshaft bolts to the diff flange with nuts and bolts, it's most likely a large axle diff. If it's bolts only and no nuts, small axles. Yes, it's easiest to simply swap the 'member', make whatever you want of the designation, lol.

If you tore up the ring/pinion gears, you can replace it with most any other one, iirc. If you don't know how to rebuild a diff, have it done by a pro.


Okay, I'm pretty sure I have the small axles then. I'm going to try to pull the car apart today and see exactly what I broke.

Everybody's input has been super helpful. this is going to be an awesome parking lot job.
Old 06-01-07, 10:49 AM
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I've had several 83's ranging from early 83 to late 83 and I'm 99.999% positive there is no such thing as a "83 1/2" all the rears in my cars have small axles but the large driveshaft flange. 83 is the mutt year on many things, this being one of them. Basically you can only replace a 83 3rd member with a 83 3rd member unless you want to start swapping other parts around...
Old 06-01-07, 11:05 AM
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Originally Posted by 82transam
. Basically you can only replace a 83 3rd member with a 83 3rd member unless you want to start swapping other parts around...

I disagree:

If you have a small axle, you can swap it with any GSL 3rd member with small axles and that goes for larger axles also. Diffy housing/bolt pattern on GSL and Non-GSL are all the same.
Old 06-01-07, 08:59 PM
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Originally Posted by wackyracer
I disagree:

If you have a small axle, you can swap it with any GSL 3rd member with small axles and that goes for larger axles also. Diffy housing/bolt pattern on GSL and Non-GSL are all the same.
Well, I spent ALL day working on this diffy thing. after some head scratching I did eventually get the thing apart and the 3rd member off. It turns out that I most definatley blew the ring and pinion gears.

There are not too many of these cars at the wrecker's here I almost lucked-out, I found a GSL diff. Although it was an '85 the drive shaft and housing/bolt pattern both match, also the teeth on the ring and pinion gears are WAY deeper in the new diff (I liked the look of those) but after bringing it back to the car I found that I did have the small axles after all.

So now my plan is to swap the carrier with the drive axle splines from the old diff and use the new ring / pinion gears and housing. I talked to a guy at a transmission shop, and he said I would need to heat the ring gear to install it on the new carrier because it's a tight press fit. I'm not so looking forward to that... but that's tomorrow's job. if all goes well I'll be back on the road by lunch-time
Old 06-02-07, 12:01 AM
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Why not go back and grab the entire rearend and save all the touble of setting up the gearset?
Old 06-02-07, 12:13 AM
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setting the gear set is not hard if you use the spacers from the oldpinion you almost never have to set the pinion depth. you only have to do this when you have a ring and pinion that are new or are from a different set. and make sure you clean the everliving crap out of that diff housing or you will be sorry. and you dont have to heat the ring it just bolts right on but becarful of the screws you need and impact screw driver i have done like 6 of these they are cake walk i can have one done in like 4 hours flat you will be sucessful dont worry.
eric
Old 06-02-07, 04:03 PM
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It's done!

I took the planetary carrier with it's smaller drive axle splines from the original differential, swapped the ring gears and installed it into the new diff housing. I didn't touch the pinion gear.

setting the ring gear and bearing pre-load was a little intimidating but I eventually got it to where I liked it - no tight spots, but virtually no play in the ring/pinion gears, and no play in the axle bearings but as little pre-load as possible.

It all went together pretty nicely - thanks to 'thegoatc' for the encouragement, I did not need to heat anything, the ring gears just slid off - and slid on.

Finally, I cleaned the housing flanges and used Loctite's 515 gasket sealer. After reassembling the brakes and tossing the wheels back on I started it it up for a gentle test ride. I put it in gear and very gently apply the clutch and begin to roll forward, and I feel something binding >.<

It turns out that I was running into the 2 by 4 I put in front of the wheels :P

Another job well done by:
Mr. Showoff.

thanks guys!
Old 06-04-07, 03:25 PM
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Originally Posted by anotherfire
and I feel something binding >.<

It turns out that I was running into the 2 by 4 I put in front of the wheels :P

LOL!


Glad it all worked out in the end.
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