How do you tell if it has the auxilary transmission? This one has only one lever that looks like a shift lever, on the right side of the transmission.
Would it be possible to install an auxilary trans, since my primary use is dozer work?
If it has an aux, there will be two sticks. The OEM option pacakge that Oliver sold was made by Trasco. Here are some photos. The Trasco package used a modified Ford Model A trans and a special made clutch housing. Some of it, the way it was done, does not make sense to me. They modified the Ford A trans with a special input shaft so the original Cletac clutch disk would fit. Why bother? Leave the A trans original and use the original Ford Model A disk which is the same diameter. Also, the Trasco setup did not allow removal of the driveshaft for repairs without an awful lot of work. You either had to cut the driveshaft off, or unbolt the transaxle and move it backwards out of the way.
I designed what I regard as a better setup. Specs to my setup have been posted for years at Cletrac.org. And, some guy came to my home, got some specs, took photos, did his own improvements and published something that's probably better written than mine.
No matter how you do it, the key is getting a Ford three-speed trans from a Model A. I've bought many for $50 or less. I've also found many laying in farm fields that I got free. The issue is - the OEM Clark transaxle in the HG and OC3 has an odd-ball shaft and spline size at 1 3/16". The only things on the planet that matches - that I know of - is the output shaft of the Ford Model A trans. Matches perfectly so the driveshaft parts fit fine.
I've built several, and all I've done - I used the original clutch housing and adapted a mounting plate to it so the Ford trans fits on. I also modified the driveshaft so it comes part and out easily.
With the Ford Model A 3 speed transmission installed as an auxillary unit, ground speeds at full throttle are as follows:
Original: 1st - 2.01 m.p.h., 2nd - 3.19 m.p.h., 3rd - 5.24 m.p.h., Rev. - 2.33 m.p.h.
Range 1: 1st - .64 m.p.h., 2nd - 1.02 m.p.h., 3rd - 1.68 m.p.h., Rev. - .74 m.p.h.
1st - 1.08 m.p.h., 2nd - 1.72 m.p.h., 3rd - 2.83 m.p.h., Rev. - 1.26 m.p.h.
Range 3: 1st - 2.01 m.p.h., 2nd - 3.19 m.p.h., 3rd - 5.24 m.p.h., Rev. - 2.33 m.p.h.
Range Rev.: 1st - .53 rev. m.p.h., 2nd - .85 rev. m.p.h., 3rd - 1.4 rev. m.p.h., Rev. - .62
Actual reduction is 2.6 in 1st, 1.6 in 2nd. and 2.2 in reverse.
Compared to a John Deere 420 crawler:
1st - 7/8, 2nd - 2 1/4, 3rd - 3, 4th - 5 1/4
OC-4 (with hi/lo in high range) 1st - 1.5 m.p.h. 2nd - 2.4 m.p.h. 3rd - 3.3 m.p.h. 4th - 5.2
m.p.h. rev. 1.8 m.p.h.
OC-4(with hi/lo in low range) 1st - .8 m.p.h. 2nd - 1.2 m.p.h. 3rd - 1.7 m.p.h. 4th - 2.7
m.p.h. rev.-.9 m.p.h.
The picture with the yellow trans and housing is the original Trasco kit Oliver sold. They often sell for over $1000 when available.