Looking for some guidance on a problem that im not sure is fixable or not. I was pulling disc in 3rd gear when there was a loud  pop and the machine stopped moving. The shifter remained in gear but when the clutch was engaged all there was was a  whirling sound near the top of the tranny and no movement. Eventually I found that forward 1-4 would cause this to happen, but 5th woud work fine. Reverse 1-4 would work fine also. I drove home in reverse . I have taken the tranny out and have not been able to go any further yet due to having surgery restrictions . Any idea what I'm looking for when I get to work on it again? Any transmission guys/ places in Northern California that might be able to help with repair/parts?

Hi, HUNTER.
In most mechanical transmissions, reverse uses an idler gear to reverse the direction of the output shaft. Seems to me that something has 'come unglued' on the 'forward' side but the 'reverse' side still works 'coz the power is routed slightly differently. I think I'd start by looking at that part of the transmission.

Just my 0.02.

According to the serviceman's reference book the idler gear Deas is talking about is actually used for the forward gears with the exception of 5th gear which bypasses the secondary gear sets.There are three possible problems,
1) the idler gear's bearing has collapsed causing it to lose mesh with the other gears.
2) Teeth are missing from one or more gears in the forward gear train.
3) The spline is stripped on the main input shaft at the first gear which drives all the forward gears. This is the most likely outcome as I have seen it happen to my D6 which has the same style of transmission.

Hi, PhilC.
Thanks for the correction. I have never seen a serviceman's book for those transmissions and have also never been inside one. I was simply going on how the majority of geared transmissions work.

Just my 0.02.

Hello Deas
Normally you would be 100 percent correct but Cat decided to use the idler gear as a further reduction for the forward speeds hence why 1st forward is 1.4 but 1st reverse is 1.8 (MPH).

is that like the british scout cars in ww2 not designed to take on the enemy but make fast advances to the rear if you made contact.

From what both Deas and Phil say, I wanted to say reverse idler gear or close by as well, from the description Hunter provided.
Which part of Northern California? I am north of Sacramento and might be able to steer to someone that could repair it for you.
Just as a side note, I think I have a NOS transmission main shaft here if needed; also have guy that has a couple of 9U's that you might be able to buy a take out transmission . JM

I knew you guys would  have lots of info on this and you came through as ususal. I located about 60miles west of Sacramento. I would like to see/buy the service book for this, as the one I have is an after market version that is scant on details.

Hello Hunter
If you join ACMOC then you will have access to the library which has a copy in it.

I am member, but when I click on the tech library it does nothing. No spinning wheel , no error message. nothing.