Hello. I'm new here. Have always loved heavy machinery and hoping to purchase my own crawler loader soon. I'm a pretty decent shade tree mechanic so I'm not afraid to tackle maintenance and repairs. Found a 1966 Caterpillar 933g for sale at a good price but owner says it won't stay in reverse under load / pops out. Any thoughts on what may be the cause and how difficult or $$ it may be to fix? Also my reading on the 933 indicates that it may share drivetrain design/components with the D4. Has anyone heard this too? I plan to use the machine for cleaning out a pond, clearing some land, improving/building farm roads and a hobby. Thanks. I value your wisdom and advice

Sounds like it could be something with the inner lock causing it. It,s been many years since I been around one but should be a 42A serial number machine first built in 1965 and I believe there was some changes to it from the earlier 933F 42A loader.The G went in production at 42A6164.I,m sure someone else on here has more of the info that you need.

The "G" model uses the rather obscure D320T engine that may be somewhat difficult to find parts for and yes they made use of D4 size undercarriage components.

I dismantled one 933 with d320 motor and the motor is sold now but am still have many parts and he had a d4 chaine and roller on.

Thanks SJ, Old Magnet, and Gemdozer. Yes it in fact is a 933 42a. Good to know there's people out there like Gemdozer who may still have extra parts for an older dozer like the 933. Also encouragaging to think D4 undercarriage parts may fit. I appreciate your responses.

Gman,

I saw that Cat, too. Told him if he didn't sell it to let me come see it. Has the wrong drivetrain for me. But I love a challenge.

I'm in St. Louis. Where are you?

David

Here is a sumation of the 933 lineup as posted by OzDozer:

The 933C was released in Feb 1956 based on the D2 drivetrain, and using D2 undercarriage.

It came with oil master clutch as standard, and the engine of the 933C was called a "special arrangement" of the D311. It produced 50HP.

The 933C transmission was identical to the D2, but the steering clutches were heavier (wider) with 12 discs. The final drive gears were the same as the D2, but the housing was 2" wider to accommodate the larger steering clutches, and the sprocket shaft was redesigned and made heavier.

The undercarriage consisted of a fixed trackframe (non-oscillating) that was 13" longer than the D2, and the tracks were basically D2, but were 37 link and used 5 rollers.

In mid-1957, at S/N 11A2163, the 933 was upgraded to D4 undercarriage, along with many other improvements.
The undercarriage overall, was seriously increased in size, with heavier track roller frames, and 2 tie bars were installed between the drawbar and traxcavator frame, to enable drawbar loading to be spread over a greater area of the frame.
This redesign was renamed the 933E (some sources say S/N 11A2251 was the 933E introduction).

In mid-1959, a major redesign resulted in an all-new 933 final drive assembly, and the 933E traxcavator became the 933F, with a new S/N prefix of 42A.
This new 933F final drive had a heavier housing, heavier bull gear hub, wider, coarse pitch gears, a bigger pinion bearing, and a heat-treated sprocket nut with a new style lock.

This final drive had no interchangeable parts with the earlier final drive, but the early final drive, could be replaced with the new style, as a complete unit.

The 933F was also released with lube-for-life track rollers and idlers, and optional, machine-specific, 3 shank rippers. In 1961, a FWD/REV lever was added, to speed up production. A Hyster towing winch was available at this time for the 933F.

The 933F was replaced by the turbocharged, D320-engine-powered, 933G in 1965, with 60HP, as compared to the previous 50HP. The 933G was built until 1968 when it was dropped from the product line.

I have rebuilt those D320s and I can,t remember for sure but seems they were the D311 that were turbo-charged and had the 4" bore engine like the D311

The 933G should have the fwd/rev on a seperate lever the trans a 4 speed possibly a bearing or twisted shaft/splines will walk it out of gear. All parts come out the top so its not a real nightmare to work on as compared to any final or ring gear work on them. I have a 933f tore down for broken ring&pinion and have threequarters of the tractor apart.Its possible cat may still have some trans parts available if not many used parts are probably out there.good list on the BB for parts check it out. good luck ,Scotty

The most common thing that caused the 42A's to jump out of forward or reverse was the F/R idler gear wearing the corners off the teeth, I have repaired a lot of them gearboxes and I would not say they are easy but the greatest SOB of all the Cats to do esp if the machine has a cab,its probably over thirty years since I done the last one and as I remember to change the idler gear the layshaft had to come out first which came out the back leaving the gears behind in the box,often the shaft splines would be twisted and would not slide through the gears and that called for the hot axe and to be able to use the torch the counter shaft had to be taken out,so I would say the greatest B of a job one would come across on any machine.
AJ