929 diff and alxe swap into a 91
Thread Starter
Junior Member
Joined: Aug 2010
Posts: 5
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From: spokane wa
929 diff and alxe swap into a 91
hi, guys ive been trying to find some info on this swap, ive been searching the site but i havnt found much. my car doesnt have a rear end, i need something strong and its cheaper than a TII diff and alxes.
Rotary Enthusiast
Joined: Oct 2002
Posts: 1,165
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From: California, Bay Area
I've considered doing this for more readily available gear ratios.
You still need a T2 rear housing and you'll need to fab up a front mount(probably weld some new mounting points to the sub-frame, shouldn't be too hard, the 929 diff has mount holes on both sides that should land nearly on top of the sub-frame.)
The problem I ran into and why I never per sued it was that the FD/RX8 pinions have 40mm bearing journals and the 929 has 35mm, so in order to use the 4.77 rx8 ratio I wanted I would either have to lathe down the pinion or find some custom bearing with a smaller ID but the same dimensions to fit the 929 housing. So unless custom work is done you're stuck with the stock 929 ratio which I believe is ~ 3.7, horrible for a rotary.
Also, since you are concerned with strength, the actual 929 diff is no stronger than the T2 diff, both are 8 inch units, and since the 929 shaft uses slightly smaller bearing journals it might actually be slightly weaker. The part people usually nab off 929's are the half shafts, which are 30mm instead of the t2's 26mm. You need two shafts from the drivers side of the 929 since it uses unequal lengths and only one Length is correct for the FC.
TL : DR
-Require custom front mount
-can't use TT/Rx8 gears without mods
-diff isn't stronger
-half shafts are stronger but require two from the drivers side of the 929
So, unless you like a lot of fab you're better off just sourcing a T2 diff and grabbing a set of drivers side 929 axles if you can find them.
Pics are a miata diff compared to a 929/t2 combo, they aren't mine I found them on a forum somewhere.
You still need a T2 rear housing and you'll need to fab up a front mount(probably weld some new mounting points to the sub-frame, shouldn't be too hard, the 929 diff has mount holes on both sides that should land nearly on top of the sub-frame.)
The problem I ran into and why I never per sued it was that the FD/RX8 pinions have 40mm bearing journals and the 929 has 35mm, so in order to use the 4.77 rx8 ratio I wanted I would either have to lathe down the pinion or find some custom bearing with a smaller ID but the same dimensions to fit the 929 housing. So unless custom work is done you're stuck with the stock 929 ratio which I believe is ~ 3.7, horrible for a rotary.
Also, since you are concerned with strength, the actual 929 diff is no stronger than the T2 diff, both are 8 inch units, and since the 929 shaft uses slightly smaller bearing journals it might actually be slightly weaker. The part people usually nab off 929's are the half shafts, which are 30mm instead of the t2's 26mm. You need two shafts from the drivers side of the 929 since it uses unequal lengths and only one Length is correct for the FC.
TL : DR
-Require custom front mount
-can't use TT/Rx8 gears without mods
-diff isn't stronger
-half shafts are stronger but require two from the drivers side of the 929
So, unless you like a lot of fab you're better off just sourcing a T2 diff and grabbing a set of drivers side 929 axles if you can find them.
Pics are a miata diff compared to a 929/t2 combo, they aren't mine I found them on a forum somewhere.
Thread Starter
Junior Member
Joined: Aug 2010
Posts: 5
Likes: 0
From: spokane wa
im not worried about the fab work, i know many people that do very good work for beer. and i can get beer cheap. my main problem is the the axles i have are 31 spline. and dont fit into my hubs. i read people get there hubs broached?
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Jeff20B
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