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Jonny Rochester
29th April 2007, 12:42 PM
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.

parrot
29th April 2007, 06:48 PM
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.

Jonny Rochester
29th April 2007, 11:18 PM
Yeah thanks. I'm hoping to get a job as engineer for Toyota oneday, because I'll put ae86drivingclub.com on my resume. http://www.ae86drivingclub.com.au/forums/emoticons/dry.gif 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.

parrot
5th May 2007, 12:12 AM
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.

Jonny Rochester
10th May 2007, 12:16 AM
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.

Jonny Rochester
10th May 2007, 12:21 AM
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

parrot
11th May 2007, 11:34 PM
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.[/b]


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

ghetto ke
18th September 2007, 10:27 AM
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.[/b]


In a previous thread "JDM ADM T 50" it was said...


Just looked into this, will do a full post in tech articles.

Our SR spec cars with 3.909:1 diff have speedo gears 20:6

GT spec with 4.3:1 diff and slightly different tyres needs 22:5 gears. The big ring on the output is N=5. The plastic gear is N=22, and you can order the seperate gear on the shaft, and is same as a KE70 part. The 5 tooth ring will only be found in a 4AG gearbox so will try and order it.[/b]

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?

orido
18th September 2007, 11:09 AM
You're a legend and a great asset to this site[/b]


so true thanks johnny this one just solved one for me

turbo_rolla
6th October 2007, 03:24 PM
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:

Konakid
11th October 2007, 12:21 AM
Also want to know if this is right! I want my speedo to be accurate dammit!

Just checked, yep turbo rolla, thats correct.

Konakid
11th October 2007, 12:33 AM
how can we identify which parts we need specifically, or actually, how expensive are these parts new from toyota?

turbo_rolla
11th October 2007, 08:34 AM
Okay, so a 21.6 gear will do it then you reckon? I rang a while ago about a new speedo drive and the "full" price was about $50, but i could get it for about $40. Will make some more enquiries though. But im also keen to work out exactly what you need to ask for (ie is it as simple as asking for a 21.6 ratio gear?).

parrot
11th October 2007, 01:47 PM
No, there are two parts.

There is a metal gear inside the box, the 5 or 6 tooth. This is $60.85 for a 5 tooth. 33481-12030

Then there is the plastic speedo drive that mates with this and is sold complete with the shaft and drives your cable This is about $49. Not sure if cost varies depending on number of teeth. The 22 tooth was easily available, may be harder to get others such as a 19 tooth, which I need at some stage. Possibly needs to come from Japan.

turbo_rolla
11th October 2007, 06:56 PM
Then there is the plastic speedo drive that mates with this and is sold complete with the shaft and drives your cable This is about $49.[/b]This is the part i initially got the pricing on (a 22 spline speedo drive). So am i correct in assuming that a 22:6 would refer to a 22 spline speedo drive with a 6 tooth metal gear for example? That much closer to getting it sorted out! Thanks!

Konakid
11th October 2007, 09:42 PM
Yes thats right! haha, Anyone know how easy it is to replace these, are the 21 splines common? cheers.

parrot
11th October 2007, 09:54 PM
Well the plastic gear on the spline is easy to replace. Essentially undo one bolt and take off the retaining tag then pull it out.

The 5 or 6 tooth is inside the gearbox, not sure how involved it is to change that but presume you need to split the case. I have not looked into that yet however.

turbo_rolla
11th October 2007, 10:27 PM
Well the plastic gear on the spline is easy to replace. Essentially undo one bolt and take off the retaining tag then pull it out.

The 5 or 6 tooth is inside the gearbox, not sure how involved it is to change that but presume you need to split the case. I have not looked into that yet however.[/b]
Had a look in the AE86 Manual (online version), and found the following:

This is the speedometer driven gear, and like parrot said, looks like a simple matter to remove as its basically where the speedo hooks up to the gear box.
Page MT-21
http://img528.imageshack.us/img528/6813/71135731hf4.jpg

This is the speedometer drive gear (different to above, as this is what drives it). From the looks of the picture (exploded version), it apepars it may be on the inside of the case, as parrot guessed:
Page MT-6
http://img528.imageshack.us/img528/7702/34191982ru2.jpg

Look forward to someone confirming this though! :2thumbs:

parrot
12th October 2007, 11:16 AM
Although note the first diagram shows the reverse light switch.

parrot
8th February 2008, 01:01 AM
I know this is old, but for completeness, I can confirm a late T18 (TE72) T50 has a 19 tooth plastic gear.

redsprinter
8th February 2008, 11:47 AM
what would i use for a w58 gear box with a 3.9 diff with 195/50/r15

Jonny Rochester
8th February 2008, 11:28 PM
You will want the gear ratio of your speedo gears to be similar to what your T50 originaly had in it, since you also have a similar diff ratio.

If your interested, you should first see what speedo gears you have in your gearbox.

riojin
28th February 2008, 12:34 PM
I'm a little confused. i have a 3.9:1 ratio diff and am using a adm cluster. i want to use a jdm cluster.

is the speedo drive gear inside the cluster?

Jonny Rochester
29th February 2008, 10:50 PM
You should not have to change anything. Both clusters are the same as far as I remember, unless I said otherwise elsewhere.

The speedo drive gears we are talking about is at the back of the gearbox.

Konakid
28th March 2008, 06:31 PM
So does anyone know how to replace the internal worm gear? Pull out the outer one and its in perfect nick, and the speedo cable isnt broken but the speedo just still isn't working.

parrot
28th March 2008, 08:54 PM
It wont be the internal gear, it is made of steel. Whereas the other gear is plastic. Possibly the cable isn't clipped into the back of the cluster properly. Try driving the car with the cluster out and check the cable turns.

The shaft isn't broken on the end of the worm drive from the gearbox?

Konakid
29th March 2008, 02:22 AM
Ill check both, cheers!