You're a legend and a great asset to this site.
I am guessing you don't have much time left to work on your car.
Note: most of my info at hand relates to Euro and USA spec vehicles. Will update this later.
There are two differences between the SR and GT spec gearboxs that I know of.
1. The bellhousing is different. Clutch on non exhaust side. One says "4AG" on the top, other says"3A".
2. The speedo gears are different according to the diff ratio and tyres it had.
Cars with the 4A-C mostly had the 3.909:1 diff (3A-U has 3.727:1). They have 185/70R13 tyres or 185/65R13 tyres or similar. And the speedo gears in the gearbox are 20:6.
Cars with the 4A-GE mostly had the 4.3:1 diff. Many had 185/70R13 tyres, some had 14" wheels with 185/60R14 tyres, and 195/60R14 was an option. The speedo gears are most commonly 22:6 ratio (suits 185/70R13 and 195/60R14 best), or can be 19:5 to suit slightly smaller 185/60/14 tyres.
The AE86 speedo cluster is 637 REV = 1KM
This is written on the front of the speedo, seen when you take the clear cover off.
Changing to factory spec speedo reading:
You take your speedo drive out. You have a 20 tooth gear and want a 22 tooth one (or 19). Some KE70s have what you need. Otherwise you can just order the gear and shaft from Toyota.
If you want the 19:5 ratio, take the shifter housing off the gearbox. Replace the metal speedo drive ring from a 6 tooth to a 5 tooth. Its a worm gear, when the shaft spins once the plastic gear turns 5 teeth. Im not sure how common the 5 tooth worm is, but its only found on some AE86 gearboxes. You may have to order it.
Plastic gear on shaft
33403-19135 N=19
33403-19155 N=20
33403-19165 N=21 (not specificly a AE86 part)
33403-19175 N=22
Metal worm gear on output shaft
33481-12030 N=5
33481-14040 N=6
Mix and match
The parts listed are all the same diameters. You can mix and match ratios, you don't have to use a matched set. You can use the plastic gear and shaft from a KE70, but you can't use the metal worm gear from a KE70. You can also find a plastic 22 gear in most KE30s, but may have to press in onto your shaft. The speedo gears from a TA22 and 1979 TE72 will not fit as the output shaft is smaller and the gears are different diameters. From about 1980 onwards (bigger output shaft), the T-18 will have compatable speedo gears, although are probably 20:6 same as AE86 anyway. With the early gearbox. the worm gear slips on and is located with a ball. With the late gearbox (all AE86) the worm gear has its own spline.
You're a legend and a great asset to this site.
I am guessing you don't have much time left to work on your car.
Yeah thanks. I'm hoping to get a job as engineer for Toyota oneday, because I'll put ae86drivingclub.com on my resume.Maybe the whole engineering degree thing would work better. Should get to that.
But better to put the right info up first time. Those new guys need something to search for when they're told to search.
Hopefully I have managed to order the 5 tooth gear today. Need to wait and see if it is available ex japan. The 22 tooth gear on shaft is available and is $49. I will have a look at some KE70's first.
Will update when Toyota get back to me regarding the 5 tooth.
I just had to redo some calculations and lookiing up of parts. I think I mislead you sorry.
If you have a 4.3:1 diff, the speedo ratio you want is 22:6 or 19:5.
22:6 is probably the common one, and easier to get. 19:5 is better for smaller diameter tyres like 185/60/14 and was used in Europe with those tyres and on GTV.
Calculate your own speedo gear ratio:
diff = 4.3 or 4.1 or 3.9 etc
D = diameter of your tyre in metres (will be around 0.580)
pie = 3.14
(1000 x diff)/(pie x D x 637) = speedo gear ratio
Find the closest ratio to choose your gears:
3.167 = 19:6
3.33 = 20:6 (3.909:1 diff)
3.5 = 21:6
3.6 = 22:6 (4.3:1 diff)
3.8 = 19:5 (4.3:1 diff, 185/60R14 tyres)
4 = 20:5
4.2 = 21:5
4.4 = 22:5
No that's fine. I will be running mine with 185/60/14's so all should be good. The guy rang yesterday and thinks they will be able to get it. Will need to find a 19 gear though
In a previous thread "JDM ADM T 50" it was said...
So to correct speedo if now running 4.3:1 (195/50/15) all I need to change is the 20 for a 22 plastic gear, or change from 6 to 5 also?
so true thanks johnny this one just solved one for me
This is a great article! Can i just confirm something though?
I have a ke70 with 4age & JDM t-50. THe ke70 came with a 3.9 diff, and it now has a t-18 diff in it (4.1?). Using the formula below, it gives me 3.5 (based on a 4.1 diff now), which would indicate that i need a 21:6 ratio gear? Is this right!
Thanks in advance! :2thumbs:
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