my neighbours 426 cat just landed over here for some cosmetic work but has been going steadily downhill. first of all the 4wd stopped working ,but before i could even begin to look at it forward went out. it was working fine in fwd and rev. , then appeared to have trouble sticking in rev ,then no fwd. any advice or place to start is appreciated sam
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Help, 426 cat tranny problem
- Thread starter samk
- Start date
willie59
Administrator
Hi samk, I added some details to your thread title hoping it will catch the eye of Cat techs and maybe get some answers for you. 
Lee-online
Senior Member
Is this a manual or powershift? I guess its a C model. How does the oil look?
Conn
Member
I can't help with the fwd - rev problem, but here's the scoop on the 4wd. This is for a 426 from the late 80's. There is a solenoid on the lower left side of the trans that lets fluid get to a clutch pack inside. The solenoid should read about 7 ohms. This is the same solenoid used on the trans neutralizer feature. My solenoid was bad, and Cat wanted $200, so I swapped it with the neutralizer solenoid located on the top right of the trans. With 12 volts on the solenoid, there should be 209 PSI for the clutch pack. There's a fitting to check this pressure by the solenoid.
You kinda skipped over Lee's question/suggestion. Which model is it? Series I & II have mechanical FWD and REV. From the B model on the power shuttle operates via solenoid controlled valves. The same goes for the 4WD from B model on.
I have problem with 4wd on my CAT 432 D.When I turn on 4wd mode, and put "reverse shift" in forward mode, I feel hard kick in the front and rear axles. I have changed the transmission Oil, measured the transmission pressure (217 psi) and check the solenoid on the transmission. What else I need to check? Thanks. The transmission is manual on my CAT. What can you say about it? Thanks.
it has a manual transmission with power shuttle. spoke to the owner about it and he now tells me that over the past couple of months that to get it to move forward he would go into reverse and back around the yard and then it would go forward . fluid level is up but does appear a bit dirty sam
well i finally got over a dose of the flu and got back to it. I changed the fluid and filter and it really did not make much difference. I stand corrected when i said that it was an electrically operated fwd/rev. I finally got the floorboards up and saw that it is a mechanical lingage hooked to the tranny. i do now find that rev. has now just started requiring alot more rpm, to get it moving sam
Lee-online
Senior Member
How does the oil look after you run it? Any foam or bubble in the oil.
When you changed the oil, what kind of debris was in the oil. did you cut open the filter?
Checking the pressures will tell you exactly whats going on inside the trans but you could remove and clean the spools in the control valve, especially the neutralizer, If this was stuck slightly open you would not move. Unplug the solenoid on it first to make sure it isn't energized.
When you changed the oil, what kind of debris was in the oil. did you cut open the filter?
Checking the pressures will tell you exactly whats going on inside the trans but you could remove and clean the spools in the control valve, especially the neutralizer, If this was stuck slightly open you would not move. Unplug the solenoid on it first to make sure it isn't energized.
nukeoperator
New Member
Does the 4wd still work? Is your only problem hard shifting when in 4wd? Which pressure did you check? Which solenoid did you check and how did you check it? Side question, I am considering downloading a Cat service manual from a company in the Ukraine called Marine Technics. They have every Cat manual as far as I can tell and several other manufacturers. I can get a pdf version for $70 USD which is cheap compared to the $500 USD that I am finding elsewhere. Any info on this company? Kind of scared dealing with an out of country company. Thanks
well, back at it. the problem with th 4wd turned out to be a messed up connector, fixed it and it at least is now working. drained the oil out and it really did not look bad, cut open the filter and really not too bad also. pulled off the oval plate to access the screen and there was a bit of crud , [very little] and the screen was not clogged . am waiting for new fluid to come in and then i will try it again and hope for the best. i will keep you posted as to outcome sam
well, finally got around to putting in the new fluid and filter and unfortunately no change[strong in reverse and sometimes strong in forward it always kicks in but no power or very little to wheels]. it does appear that the fwd/reverse leaver beside steering wheel is just connected to a leaver on top of the tranny and i am assuming moves some internal valve . I am going to do a pressure check next and understand that there is a port somewhere near the filter but am really not sure where.also should i be taking the top of the fwd /rev lever and also what should i be looking for. i now have acquired a parts book and may require a repair manual but my god they are expensive thanks to all for your help sam
i finally got around to pulling it out and tore it down. the discs were toast, a seal on one of the pistons was mangled, aND THE REAR cone bearing on the clutch pack was showing some wear. i have sent the converter out to be checked over .my concern now is how to determine the number of shims that i require to set the proper clearance for the rear clutch pack cone bearing, as stated the hoe is a 426 and the serial # starts with 7BC thanks sam