Terex 72-31B Weak Transmission

My grandpa has an old Terex 72-31B with an Allison transmission that was just rebuilt this last winter. It doesn’t have enough power to spin the tires in sand. When the transmission worked good before it went out it had lots of power. We probably only have an hour on the rebuild and are wondering if there’s anything that needs to “break in” for it to work good or if anyone has any ideas. We will probably have to have the guy who rebuilt it look into it but I’d just like to get some different peoples ideas and opinions. I know there are specific procedures for checking pressures and etc. Also we are running sae 30 oil in it so we should be good there. Please let me know what you guys think, there’s probably not many people around that run these old terex loaders, thanks.

There is no break in period on any power shift transmission that I am aware of. For some reason I seem to remember those using some kind of automatic transmission fluid or tractor hydraulic fluid. Hopefully someone will come in a correct me if I'm wrong.

He had put tractor hydraulic fluid in but then we drained it and put sae 30 in to see if it made a difference. It helped but not enough. I’m starting to wonder if the transmission cooler is plugged with debris or something

If the original trans came apart inside somewhere, as in made pieces of itself, you should have definitely flushed the trans cooler. The risk of sending shrapnel through your newly rebuild trans is high.

John C. said: There is no break in period on any power shift transmission that I am aware of. For some reason I seem to remember those using some kind of automatic transmission fluid or tractor hydraulic fluid. Hopefully someone will come in a correct me if I'm wrong. Click to expand... They used to John but now they have gone with 30wt., at least on the rear dumps anyway

Both the cooler and pump should have been part of the rebuild process. If there was metal circulating in the system then the pump could have internal damage just as easily as the cooler could be plugged, or even the cooler bypass valve if there is one.

Ok, I’m not sure why the mechanic didn’t take the cooler off as well, but that’s probably the issue. Hopefully the rebuilt trans is not screwed up from metal. There was definitely a lot of metal in the system when it went out because a bearing in the torque converter went out and chewed everything up.

Were any pressure measurements done after the transmission was reinstalled.? Was the pump ever inspected.?

Nige said: Were any pressure measurements done after the transmission was reinstalled.? Was the pump ever inspected.? Click to expand... He did put a new pump on before the trans was reinstalled. Haven’t done any pressure checks after but there is a gauge in the cab for the “Torque converter pressure” which has been reading above the normal maximum pressure.

Was the torque converter itself replaced or rebuilt as part of this job? Given that's where the original bearing failure happened, it's worth confirming it was properly addressed, too.

DustAndRay said: Was the torque converter itself replaced or rebuilt as part of this job? Given that's where the original bearing failure happened, it's worth confirming it was properly addressed, too. Click to expand... Yes he rebuilt the torque converter

CrusherRatN14 said: My grandpa has an old Terex 72-31B with an Allison transmission that was just rebuilt this last winter. It doesn’t have enough power to spin the tires in sand. When the trans Please let me know what you guys think, there’s probably not many people around that run these old terex loaders, thanks. Click to expand... Allison runs on Dex!n11 or better

Nige said: Were any pressure measurements done after the transmission was reinstalled.? Was the pump ever inspected.? Click to expand... In correct oil Nige too heavy