M917-7155 tranny woes.

[Abrant23]

Morning everyone!

I have a bit of a problem with the transmission in our 917. Yes, I’m going to study up on the TM’s, but I figured I might as well start a thread to document my plight. Also would like any guidance you all could offer along this journey I fear I’m about to take!

Well, here it goes. Boss man calls me yesterday afternoon and tells me the 917 “quit going”. Claims he downshifted to take a 90 degree corner, and the transmission disengaged. He coasted to a stop (in the middle of a back road in the national forest) while trying to figure out what was going on. I drove out to meet him and find that the transmission will not engage in any of the forward or reverse gears. Also the pto, when engaged, is not turning the hydraulic pump. When you shift thru each of the gears, you can feel it start to engage, for a split second, then nothing. We hooked the truck up to the back of a dually and drug it out of the middle of the road, where it spent the night.

This morning I came out and swapped the ratio selector out with another one we have. This didn’t change anything.

According to the quick browsing of the TM’s as I sit and wait for a tow truck, it looks like I’m not getting engagement from the input clutch pack? Has anyone had this issue? It looks as if testing the input clutch is a “remove the transmission” ordeal. Other than testing the oil pump pressure, is there any other recommended steps to take before jerking it out from under the truck?

Any insight would be greatly appreciated!

 

[NDT]

Couple things. When you push in the transmission pressure charge button are you getting the usual kerthunk? Assume you have at least 90 psi air to the transmission? Did you try injecting some oil in the air line feeding the transmission? Issues with the 7155 are usually in the valve body, which can be replaced without removing the transmission. The valve body, however, is a nightmare to rebuild. Try to find a replacement if you decide that is the issue.

 

[Abrant23]

Couple things. When you push in the transmission pressure charge button are you getting the usual kerthunk? Assume you have at least 90 psi air to the transmission? Did you try injecting some oil in the air line feeding the transmission? Issues with the 7155 are usually in the valve body, which can be replaced without removing the transmission. The valve body, however, is a nightmare to rebuild. Try to find a replacement if you decide that is the issue.

Yes, to all of the above. It kerthunk kerthunks through all the gears, including reverse. We keep it oiled as well. It slightly lunges in each gear, but it won’t engage completely.

I’m going to start going thru the steps in the TM for troubleshooting this weekend.

 

[Abrant23]

Well, here’s a fun one. Looks as if I’ve had a major oil pump failure. Seems as tho whatever caused it had been going on for a while before it finally gave up.

I guess it’s going to be a total tear down and rebuild on the non-air side of things. Wish me luck!