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1987 Toyota Supra
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That's a heck of a deal.
 

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It does not matter. The pinion flange is square, 60x60mm pattern.
Side shafts are not clocked either to a specific orientation.
Just make sure you torque all bolts to the correct ft/lbs as in the TSRM.

If you separate the 2 part driveshaft, that is the critical part to put back together the same way again.
The diff, does not matter.
Usually there is a rust shadow of oxidation on the companion flange. Put your driveshaft on so it matches the orientation. I think the torque is 54 foot-pounds. I usually do it in 2 steps. I've been having good luck with Castrol limited slip differential oil 80W-90. It's already got the additive, so one less thing to buy. You can confirm your differential ratio by using tape on a side gear flange and hand rotating the companion flange until the tape mark on the side gear has made 1 revolution. I'm not sure where Toyota made the adjustment on the speedometer whether it's in the gauge cluster or at the transmission's plastic replaceable gear. Seems like I had a leak there and I replaced that gear without removing the transmission. You would have to compare W58 versus R154 parts and it would be the 89 to 92 part for a 3.73 final ratio. When you're on the highway look at your GPS speed versus the speedometer.
 

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Discussion Starter · #23 ·
Usually there is a rust shadow of oxidation on the companion flange. Put your driveshaft on so it matches the orientation. I think the torque is 54 foot-pounds. I usually do it in 2 steps. I've been having good luck with Castrol limited slip differential oil 80W-90. It's already got the additive, so one less thing to buy. You can confirm your differential ratio by using tape on a side gear flange and hand rotating the companion flange until the tape mark on the side gear has made 1 revolution. I'm not sure where Toyota made the adjustment on the speedometer whether it's in the gauge cluster or at the transmission's plastic replaceable gear. Seems like I had a leak there and I replaced that gear without removing the transmission. You would have to compare W58 versus R154 parts and it would be the 89 to 92 part for a 3.73 final ratio. When you're on the highway look at your GPS speed versus the speedometer.
Actually, that's what I did when I matched the driveshaft flange to diff flange (the rust shadow was very visible). 54 ft lbs per TSRM; and used Royal Purple 75W-90 gear oil - already has the friction modifier as well.
Test drive went really well. Driveline was smooth all the way up to freeway speeds. I was pleasantly surprised when the small clunk that I hear when on/off throttle at slow speeds went away.
For determining speed, I downloaded a chart showing MPH based on gearing, RPM and tire size.
I'll look into the plastic gears to see if those can correct my speedometer, thanks for the info.

260176
 

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Keep in mind that you'll be losing some acceleration and showing slower than actual speed with the gearing change from a 4.30:1 (MK3 NA) to a 3.73:1 (89-92 Turbo).

The old school way to fix this was with a speedo 'bug' that would step up or step down the gearing accordingly so the speedo cable would spin the right speed, but I suspect that's a lost art these days. You'll have to do the math and mentally adjust to know true MPH vs indicated MPH. This will also affect your odometer.
Can you still get replacement speedometer drive gears for the transmission output housing? I remember that was a thing, back when I had a stock cluster.

Also, this is what it sounds like if you run it to 8000 rpm, in fifth, with a 4.10 diff, for the sake of science. Yeah, science:

 
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