CAT 420D barely crawls up the hills

New to CAT and this forum. Recently purchased '06 CAT 420D (4200 hrs, 4WD, FNR shifter, 4 speed) that has strong and very responsive hoe and bucket hydraulics, but slows to a crawl when climbing even a very modest incline at full power. RPMs hold steady under load, but will only climb an incline in 1st gear; 2nd gear will bring it practically to a stop. Speeds and responsiveness seem normal on level ground, with AWD engaging as it should. Transmission fluid (TDTO-30) and filter were changed, with screen cleaned, but fluid looked/smelled good with no filings on magnets. I sure hope this isn't normal for a CAT backhoe, but don't believe it is. I'm not sure where to start looking to diagnose/fix the problem. Suggestions very much appreciated.

sounds like torque convertor is going out clean strainer on shuttle and see if it helps

Dave Neubert said: sounds like torque convertor is going out clean strainer on shuttle and see if it helps Click to expand... The screen at the bottom of the transmission pan was essentially clean, with very little sediment and no apparent debris from internal parts. Is that the screen you're referencing?

I believe I would check clutch pressure

koenigs53 said: The screen at the bottom of the transmission pan was essentially clean, with very little sediment and no apparent debris from internal parts. Is that the screen you're referencing? Click to expand... yes

Dave Neubert said: yes Click to expand... OK. Thanks!

How good did the fluid look? Could be previous owner was having issues and pulled pan and screen was full of clutch material and cleaned and refilled. Then sold.

HarleyHappy said: How good did the fluid look? Could be previous owner was having issues and pulled pan and screen was full of clutch material and cleaned and refilled. Then sold. Click to expand... Is the oil light or dark in colour.? Does it smell burned..?

HarleyHappy said: How good did the fluid look? Could be previous owner was having issues and pulled pan and screen was full of clutch material and cleaned and refilled. Then sold. Click to expand... I've wondered the same thing. It did look to be in good shape, with no burnt smell to the oil, and the filter had clearly not been changed in a long time. So, it appeared somebody changed the oil, but not the filter.

Nige said: Is the oil light or dark in colour.? Does it smell burned..? Click to expand... The oil seemed to be in good condition, with no burned smell. Filter looked like it had been on there for quite a while, so it's possible they just changed oil and not filter.

pittsburgh cat man said: I believe I would check clutch pressure Click to expand... I had a local repairman tell me that it might be due to a dirty fuel filter, not allowing sufficient fuel flow when needed. I intend to change it tomorrow. If that doesn't help, I'll move on to clutch pressure. Thanks.

What does the air filter look like? Do you have any exhaust leaks before the turbo?

How much time on a backhoe?

Did you check for leaks? if the transmission sucks in air you have the same effect. after replacing leaking seals on the transmission you lift the axles in up and let the wheel spin slowly in all gears and forward and reverse to bleed the air out of the system. As you don't know what happened to the machine before the chance that this is the solution is not too likely , but it is much cheaper than a rebuild

It seems very unclear if you have a engine problem or a transmosson problem. Is the engine lugging down or is the machine just slowing and the engine rpm holds steady

Tyler d4c said: It seems very unclear if you have a engine problem or a transmosson problem. Is the engine lugging down or is the machine just slowing and the engine rpm holds steady Click to expand... he said rpms hold steady under load

Deere500a said: How much time on a backhoe? Click to expand... 4200 hrs

pittsburgh cat man said: What does the air filter look like? Do you have any exhaust leaks before the turbo? Click to expand... Air filter is good; haven't checked for exhaust leaks, but will do so today. Thanks.

Dave Neubert said: he said rpms hold steady under load Click to expand... I seen but hes also got advice to change the fuel filters

To all, I replaced the fuel filter today and it made a huge difference. I'm not certain that I've resolved all of the problem associated with lack of power under load, but it went a long way toward bringing the ground speed back up to about what i believe should be normal. Thanks to all. P.S. It solved one problem, but raised another, which I might start in a new thread if i can't figure it out. Thanks, again. This forum feedback has been quite helpful.