TH400 speedo gear for bigger rims?

[g356gear]

I have switched to 18" rims and a 35 series tires and was curious for opinions on what tooth number gear I should switch out to for my speedometer to be more accurate because it seems to be waaay off. I am running 3.37's and a Turbo 400.

[Jake's Performance]

What is your actual tire size. I need a complete tire size or the actual diameter and I can figure what speedo gears you need.

[g356gear]

What is your actual tire size. I need a complete tire size or the actual diameter and I can figure what speedo gears you need.

25.58" overall tire diameter with 3.37 rear gears

[Jake's Performance]

You need a 15/40 combo.

The 40 tooth is no longer available from the dealer.

So you could go with the 15/39 or 15/41 15/39 is slightly closer.

[g356gear]

You need a 15/40 combo.

The 40 tooth is no longer available from the dealer.

So you could go with the 15/39 or 15/41 15/39 is slightly closer.

Is this a fairly easy swap out? I have never really had to change speedo gears before. Usually on e-bay they just have single gears, how do I find a combo?

[Jake's Performance]

Yes,
It's pretty easy to swap. You may be able to save yourself some hassle by looking at the existing drive gear on the output shaft. If it is plastic it is colored and from the color we can tell the tooth count.

We also need to know which sleeve you have, the housing that holds the driven gear.
There are two different sleeves, one for up to 39 teeth and another for 40-up.
Those are somewhat expensive. The gears are relatively cheap.

You also would want new seals, etc while you are there.

[g356gear]

Anyone have a service manual PDf on how to do the swap?