Differential Ratios and Options

[drjonez]

MKIII Diff Offerings

'86.5 - '90 GA70s w/the 1G-GE have a 4.56, clutch-pack or Torsen LSD 7.5" differential, NOT compatible with any of the other A70 diff setups.

All 1G-GTE equipped GA70s have a 4.56, clutch-pack or Torsen LSD differential.

'86.5-'92 MA70 N/A MKIIIs without Sport Package have a 4.30, open differential.

'86.5-'92 MA70 N/A MKIIIs with Sport Package (TEMS & headlight washers on '86.5 - '88 : TEMS & PPS on '89-'92) have a 4.30, clutch-pack LSD differential.

'87 - '88 MA70 turbo MKIIIs have a 3.91 clutch-pack LSD differential.

'89+ MA70 turbo MKIIIs have a 3.73 clutch-pack LSD differential.

'90 - '92 JZA70 Limited and R MKIIIs manual trans cars have a 4.10 Torsen LSD differential and auto trans cars have a 3.91 Torsen LSD differential.

Note that a LSD was an option- so you could get a NA base model w/a LSD.

[drjonez]

Its a little known fact that the '80s toyota truck diffs use the same 8" (actually 7.8") ring gear. This opens a world of possibilites as far as diff ratio. Richmond Gear and others offer aftermarket ring/pinion sets for the truck diffs.

I am not sure about actual diff unit compatibility (splines, etc). I'd venture to guess the form factor is the same, but the output spline pattern may be different...

EDIT 12/20/04: it looks like the V6, 4 pinion, "large hub bearing (50mm dia)" diff units should be directly compatible w/the A70 diff casing.

[drjonez]

more truck info:

http://www.4x4wire.com/toyota/tech/supra_lsd/

http://www.precisiongear.com/diffs.htm

http://home.4x4wire.com/erik/diffs/

http://home.4x4wire.com/erik/toyota_info.htm#TADs

http://www.off-road.com/toyota/tech/other/4_axles.html

[drjonez]

http://www.reiderracing.com/differentials.htm

http://www.drivetrainsuperstores.com...2.asp?axle=135

[drjonez]

looks like the MKII guys use the 7.5" truck diffs:

http://www.celicasupra.com/phpBB2/viewtopic.php?t=12739

[drjonez]

pretty sure these diff units should be compatible:

Tractech Detroit Locker 187SL61B
Tractech Detroit Truetrac 913A321
Tractech E-Z Locker 813A028

[drjonez]

whelp, i have a 913A321 truetrac in my possession and it's NOT a drop in affair. problems w/the MA70 clutch pack diff casing:

-the MA70 stub axles are too short
-the MA70 stub axles are too large in dia to fit into the truetrac

i'll be checking the JZA70 torsen stub axles in the future...

[drjonez]

good old limey on SF came up w/this:

http://www.supraforums.com/forum/sho...d.php?t=311249

compatible ring/pinion guide (right click, save as)

[drjonez]

http://trdparts.jp/english/parts_lsd_mechanical.html

http://trdparts.jp/english/parts_lsd_selective.html

[drjonez]

well, i've given up on the truetrac:

truetrac does not have grooves for the retaining clips on the stub axles.

truetrac and a clutchpack, notice output height differences:


stub axle not fitting into truetrac:


offset of the ring gear flange: