934A2 dies when shifted into forward gear, but not reverse.

We unloaded a 934A2 this week, started it up and backed it off of the trailer. It runs good and sounds good.....

The air tank drains were left open and do not seal, so the truck does not build air pressure. The brakes are caged however, so it rolls freely. When we backed it off of the trailer, it pulls itself fine, when dropped into any of the forward gears, it dies immediately. Put it in neutral and it will fire right up.

Do these trucks have an air safety built in now? Kind of odd... Glen

Glen...my M923A2 suffers from that as well.....still trying to work thru it...several threads here on M939 SERIES allison problems....I feel like they are all similar is the problem...stalls or VERYslow off the line til it gets rolling. Once we find the issue i feel like we will solve several members problems. Stay tuned.


SEMPER FI!!


keith

Mine was doing this the other day. Turned out it was outta fuel. Would run real strong on N but soon as you put it in drive or reverse it would die

Just bought a truck and could not drive it home because of this exact same issue... Would love to know how to fix this problem so I can get it home!

Wonder if it could be a torque converter issue?

Mine must be different than the rest of yours as it will back up easily on three flat tires, drive though, shuts it off immediately. The engine dies as if the fuel was turned off. I guess I should watch the shut down solenoid.

Mine acts the same way but I did not try reverse?

Try putting the transfer case in low range then first to see if it will go forward.

quickfarms said:

Try putting the transfer case in low range then first to see if it will go forward.

Click to expand...

It will back up in low range, but will not go forward, the engine dies as soon as we shift. It does not sound like it does any fluid drive at all, no U joint movement, no lugging, no idle drop, nothing, just like you turned the fuel off.

My M931 A2 did this the other day. I must have bumped the transfer case lever with my boot. After cycling the transfer case up and down several times (with the truck off), it cured the issue.

Any news on what folks having issues have done? I'm wondering if the torque converter is locked up if that wouldn't cause the truck to lurch and stall when put into gear. I have a similar problem with my M936. It didn't start until I crossed some train tracks that jarred the dookie out of me and it. After that it developed issues but since I parked it, it just stalls after I start it and put it in any gear. My knowledge is limited and I have been trying to research and gather as much info as possible. I also wonder if it might be the 5th gear lock in solenoid. I was just checking to see what others have tried or figured out.

I am going to try and get my truck tomorrow which is having the same issues... I have recruited the help of a diesel mech who's been with UPS for 17 years... He has a few ideas of what could be wrong... I will advise if we get it straight!

It sounds like the torque converter is locked up. This can either be a mechanical issue or electrical issue. The first step would be to check the operation of the switch, be sure to remove if and make sure it is moving and not stuck. If this does not solve the problem it is probably a bad torque converter or lock up piston. For either one the transmission will have to be removed.

I have had the same issue. All it was on the transfer case shifter the button was stuck in. Try to pull it out gently with pliers.

I have checked the transfer case button....have engaged and disengaged the transfer case in the low/high range and my truck still is slow to move when pedal is depressed EXCEPT in reverse. It has instant throttle response in reverse. Seems to be a common problem. I'm working thru the process of trouble shooting...will advise if (when) i come up with anything.


SEMPER FI !!


keith

It's a shot in the dark but just maybe ... Did you check the Emergency Shutoff Valve? It is activated on the dashboard by pulling the Emergency Shutoff knob on the lower right side, BUT it has to be reset under the hood.

That was something another SS member posted as something to put on the checklist for picking up an newly acquired truck. I have gone through all the TMs I could find (and there are a bunch thanks to SS, and I do mean thanks) and the only thing they say is that if it is pulled, the driver/operator must have it reset by maintenance personell.

To reset it, follow the cable down to its end behind the injector and make sure that it is all the way forward.

You guys having trouble like this scares me 'cause I'm about to bring my M923A1 home after sitting in my daughter's backyard in Texas since Thanksgiving, 2012.

KaiserM109 said:

It's a shot in the dark but just maybe ... Did you check the Emergency Shutoff Valve? It is activated on the dashboard by pulling the Emergency Shutoff knob on the lower right side, BUT it has to be reset under the hood.

That was something another SS member posted as something to put on the checklist for picking up an newly acquired truck. I have gone through all the TMs I could find (and there are a bunch thanks to SS, and I do mean thanks) and the only thing they say is that if it is pulled, the driver/operator must have it reset by maintenance personell.

To reset it, follow the cable down to its end behind the injector and make sure that it is all the way forward.

Click to expand...

I was going to say the exact same thing. The truck will go backward but will either stall or go forward with no power. Just make sure that lever on the injection pump is manually pushed back forward all the way. It's worth a try.

I posted that shut off valve several times, it is not hooked to the shutdown cable at all. These 8.3 engines look like they adapted the shutdown from the 250 and all of the cables look bent.

I have checked the shut down cable/ reset.....i have removed the solenoid as it was NOT resetting which resulted in hard to no starting. Problem is only when the truck is moving FORWARD from a dead stop. Once rolling it shifts fine up and down the range. But depressing the pedal from a dead stop produces nothing and then a very slow rolling start. Fuel filters changed with no improvment. And the quest continues.



SEMPER FI!!


keith

So, the engine keeps on running, but your truck is slow to start rolling?