69 Jeep T18 changing gears.

I have a T18B (i.e. like the T18A but with only the 4:1 1st gear instead of 6:1. It's in a modified Jeepster with the V-6 and mated to a dana 20.

I have opportunity to get the gears from a T18A (i.e. with the 6:1 ratio), but I am concerned about not being able to use them -- all the threads about variety of input and output shafts concern me. (I don't have mine a part, so I don't have the length of the shafts).

Does anyone know if the input or output shafts are different with the 6:1 gears? i.e. can I keep my original input / output shafts and simply change the other gears and be OK. (big concern is if the driving gear on the cluster changes -- if so the input shaft and gear would be different too).

thanks, Mike N.

 

Mike, there's no practical way to change it by swapping gears.

The 4.02: 1st transmission is the close-ratio (CR) T-18. The 6.32:1 1st transmission is the wide ratio (WR) T-18. All the ratios except top gear are different between them, not just 1st gear. This means that none of the gears from the CR transmission mesh with gears from the WR transmission. Only one WR transmission has the same input shaft length as the CR transmission, and it was used in Jeep Wagons and pickups with the T-18 and 258 engine only, from 1971 to 1979.

If you found one of those J-truck 258 transmissions, you could swap all the gears onto your mainshaft and into your case, but then why bother? Just swap in the whole transmisison. But this only works with that specific T-18, not with any other of the more widely available T-18s.

 

Basically what Timgr said.
Your input gear with the 4.02-1 first gear has 23 teeth. The 6.32-1 input has 17 teeth. You can re-use your output shaft. No change there. The first gear slider and reverse idler gear iirc are the same. Possibly the 3rd speed gear is the same, I can't remember for sure on that. Everything else is different. I've done this swap before and it was easy to do, not easy to locate the right input gear because of locating the correct length/spline count.

 

Another question, what is the T-18a out of and do the parts come with the input gear? If it's Ford then you could put all the Ford guts in your case and do away with the adapters I'm assuming you have on the front. You may have to modify the transmission case, bellhousing, and use and modify the Ford front bearing retainer but it's do-able. Also remember if you do away with the adapters you may need to do some driveline work.

 

It's out of a CJ6 (don't know what engine). It would include the input shaft, but that doesn't do me much good since I don't know what size the input shaft I have now is. The PO did the present conversion to the T18.

the input shaft was my main concern. I was hoping that the WR came from changing the 'other gears on the cluster' - not the one that is driven by the input shaft.

I don't really need to do this, but the price was right and I figured if I ever have the transmission apart, I could swap them in. So because of the input shaft it is a risk that it wouldn't work for me.