JD440 "big" versus "little" transmission

[Gil]

A little knowledge is a dangerous thing. I was going along just fine in my repair job until I read an old message board post today from Lavoy. About this time a year ago, a member was asking about substituting a M4256T transmission for the diesel T11396 transmission. Lavoy commented, “I commonly refer to them as ‘big’ or ‘little’ transmissions. All diesels, and gas crawlers built after the diesels came out had big transmissions, all prior gassers had the little transmission. The two transmissions will NOT interchange without an extensive amount of work.”

I have spent the last month and not an insignificant amount of money rebuilding a ‘little’ transmission and I intended to put it in my JD440 ICD this week. Everything seemed to be coming together fine. It mated up with the direction reverser and I have installed the steering clutch housings and they appear to fit as well. What am I missing?
I realize that the lighter transmission housing might be more prone to breakage with the diesel’s power, which is why they changed it in the first place. But will I run into any problems mechanically? I am hoping Lavoy that your concerns were in swapping around parts inside the transmission housings rather than swapping out the transmissions in total. Anyway I would rather have the bad news now, instead of when I have the rear end swinging from a chain hoist and find that I cannot force it to slide into place.

[CELSESSER]

Gill,

If I remember correctly the term Big and Little refer to mainly the larger ring and pinion gears in the "Big" tranny. Possibly the other gears are heavier also. I believe the case dimmensions are the same and in fact they had to machine more of the case out to fit the bigger ring gear, consequently the approx. 3 x 5 inch rectangular cover plate under the seat that covers the spot they had to machine out. Also the big transmission has the dipstick in the front left corner.
So the small transmission should fit and work, but the ring gear is not as strong, thats why they changed.
I'll trade you my track pads (out of a limestone quarry = 1/2 inch grousers). They are my drive train stress relif mechanisms.

Chuck

[Howard Yoder]

If it bolted up to the reverser I would say you had the little tranny to begin with but Lavoy will know for sure.

[Lavoy]

It is not just a function of case strength, it is the entire transmission. The case is heavier, the R & P is bigger, all shafts and gears are stronger, heavier, bigger. My guess is that the Detroit will eat a small transmision in relatively short order if worked hard. I think once you try to hang the engine, you will start to find that bolt holes do not line up and things like that, I am pretty sure that the case is about an inch longer on the big transmission.
Lavoy

[Gil]

I measured the transmission cases and the 'big' transmission is in fact nearly an inch longer than the 'little' one. I wonder where they made up for the length difference. Was the new direction reverser shorter? Were the frame side rails longer? Or did the difference just hang out the rear of the tractor?

[Lavoy]

The frame rails are different to compensate for the extra length.
Lavoy

[Gil]

OK thanks for all the good advice so far. This is how things stand. I now have completely rebuilt a ‘little’ transmission and matching reverser. Howard, you were right about not bolting up to the ‘big’ reverser. I did not mention that I changed that too.

Scenario #1: Lavoy, I am not too concerned about tearing up the transmission with the diesel’s power. I use it sparingly, and when I need to use lots of power it is usually for the hydraulics for lifting not for pushing with the tracks. I do have an extra shorter set of side frame rails that I could bolt on the 440ICD to accommodate the shorter ‘little’ transmission. It looks like I would need to slide the whole loader forward to fit the new frame rail mounting locations but it looks like it would work. Is there anything else I am missing? I would save my investment in a fully restored ‘little’ transmission and direction reverser.

Scenario #2: Since my ‘big’ transmission case is cracked and welded, and the ring and pinion are not good, I would need to buy a different case, and a different ring and pinion, or ideally a fully functional transmission. Is such a creature even available and at what a cost? Then for the direction reverser I would need to either replace it completely or can I make my ‘little’ one to fit?

The second scenario gives me the best end product, but the components may not even be available or would be very expensive. Scenario 1 is a lot cheaper, but is a lot of work, results in a less desirable configuration, and I do not know if I will run into other technical impossibilities trying to implement it. Anyone have any thoughts (or perhaps a cheap transmission)?

[Lavoy]

You will have to drill different mounting holes for engine mounts and such I believe, not sure what other differences there are in the short frame rails.
Lavoy

[Gil]

I verified that the engine mounting holes are the same. This is because the engine is in the same relationship to the front of the crawler. It is only when you get back to the cross bar that things change because with the 'big' transmission the whole loader and track system had to slide back one inch in order to bolt up to the final drive housing. With the shorter frame rails it "looks" like I can "just" reposition these one inch farther forward.

I have to chuckle when typing the word "just" as if it will only take an hour or so. I have to remove the grill and hydraulic tank, remove the engine, remove the skid plate, swap the frame rails, move the track system and the loader.