transmission determination - how to determine final drive ratio?
 

Sometimes, with an older reworked Geo, there may be some confusion as to what transmission is actually in the car. I want a simple test to determine what transmission is in a Geo, and I need help. If we pull the plugs, place in 5th gear, and push the geo one full rotation of the wheels, how much crankshaft rotation would there be for a regular geo transmission, an xfi transmission and a suzuki swift transmission?

gwahir -

Don't know how to help, but I do know that on Saturn S-Series, there is a serial number on the tranny that is matched to a serial number on the engine block. If the tranny or engine is swapped, the serial numbers will no longer match.

Are there any serial numbers on the Geo tranny?

CarloSW2

I'll see what I can dig up tomorrow and post back.

The gear ratios are all the same for these cars - only the final drive is different.

5th is 0.757

Final drives:

4.39 - 1.0L garden variety (1995 and up), 13 inch wheels
4.105 - 1.0L garden variety (1989-1994), 12 inch wheels
3.79 - 1.0L XFi (1989-1994), w/12 inch wheels
3.523 - 1.3L SOHC (1989-1994), w/13 inch wheels

So multiply 0.757 by each of those final drive numbers, and that's how many times the crankshaft will rotate for one full revolution of the wheel.

EG. 4.39 * 0.757 = 3.323 crank revolutions per wheel rev.

Thanks. To me, very useful information.

Good luck - let us know what you find out.

Checking final drive -- please help me troubleshoot
 

So I read this thread on final drive ratios, wanting to confirm that the transmission in my Geo that I pulled from a Suzuki is indeed a 3.52 final drive. I duly lined up my timing mark, raised the RH wheel (LH on ground), chalked the wheel, set the car in 5th gear, and turned the crank one full 360. The RH wheel made approx . 75% (maybe 77%) turn. This doesn't correspond the potential results this thread as I understand it -- what am I missing?

Your input is appreciated!

A bit bassackwards! Remove plugs, place in 5th gear, push the geo for timing mark to tdc, mark the wheel, then push the geo for one rotation of the wheel and observe the rotation of the crank shaft. Life is better here if your timing cover is history! According to the notes on this thread, you should get 2.66 turns on the on the crankshaft for one turn of your wheel using the suzuki transmission. That would be 1.33 turns on the camshaft; easier to see!

With only one wheel turning, the differential is skewing the results. Both wheels need to turn together.