engine braking

[TedO]

My M1008 engine brakes in 3rd gear until it hits 35 mph, then it breaks loose and free rolls until stopped. In second gear, I dont get any engine braking. In first gear, it engine brakes all the way until stopped. Anybody know what is going on? I would expect to always have it engine brake/downshift until stopped.

 

[Gripy]

Im pretty sure it would be your transmission failing

 

[TedO]

other than that, its seems to be running fine. I already put 3000 miles on it and nothing has changed. Its not slipping and it pulls OK.

 

[cliffyp]

From the ATSG service manual:

Looks like you've got some internal problems

 

[Skinny]

IIRC, you will get engine braking in 2nd gear when the gear selector is in the 2 position. You WILL NOT get engine braking in 2nd gear when the selector is in D range. The difference is a one-way sprag brake is freewheeling in one direction versus an actual hydraulic brake holding the gear. I'm not that familiar with a TH400 but it is pretty common operation for any Simpson 3 speed plantary gearset which is really 99% of non-overdrive and most overdrive auto transmissions.

Does this feel different in operation than the way the truck drove before? It may just feel like the torque converter is staying "coupled" together at a higher vehicle and engine speed and then it becomes a little more loose at lower speeds.

 

[TedO]

when my selector is in 2nd, I get no engine braking. When in drive, at 35mph, tach drops suddenly to idle as it free-rolls. Always at 35 mph. In 1, I get engine braking all the way to a stop. It doesnt feel like the torque converter being a little loose. When it breaks free, it is a very sharp transition.