High RPM’s

[01GRANDER]

I just got a 07 m1152 and I was able to get it out of limp mode, it wasn’t getting power. The guy that bought it started cutting everything and disconnected some of the cables and snipped others.

Once I got it out of limp mode, I took it through all 4 gears but at 62mph, I was at 3300-3400 rpm’s.

Anything I should check out? I disconnected the glow plug controller, bridged A and E but I’m just getting 12 over and over so no errors.

 

[NDT]

That rpm is similar to what a 3 speed HMMWV sees at that speed. Maybe not going into overdrive (4th).

 

[01GRANDER]

That rpm is similar to what a 3 speed HMMWV sees at that speed. Maybe not going into overdrive (4th).

It feels like it. I go into 4th and then it slightly kicks down and drops 200 rpm’s. But I do feel it shift 3 times.

 

[diesel_dave]

It feels like it. I go into 4th and then it slightly kicks down and drops 200 rpm’s. But I do feel it shift 3 times.

Any chance one of the "shifts" is really the torque converter locking?

 

[01GRANDER]

Any chance one of the "shifts" is really the torque converter locking?

I guess it’s possible, I honestly don’t know much about transmissions and fixing them. I got lucky with figuring out the wiring but I figured it would throw some code if something like that was broken.

 

[Action]

I guess it’s possible, I honestly don’t know much about transmissions and fixing them. I got lucky with figuring out the wiring but I figured it would throw some code if something like that was broken.

It wont give a code if you are in the wrong gear. Could the shifter linkage be messed up?

 

[TOBASH]

What differential gears are you running. You have a late model so you certainly don’t have 2.56. If you’re running 3 or higher then you will drive more slowly at a higher ROM.

 

[Action]

I just got a 07 m1152 and I was able to get it out of limp mode, it wasn’t getting power. The guy that bought it started cutting everything and disconnected some of the cables and snipped others.

Once I got it out of limp mode, I took it through all 4 gears but at 62mph, I was at 3300-3400 rpm’s.
Anything I should check out? I disconnected the glow plug controller, bridged A and E but I’m just getting 12 over and over so no errors.

For reference, at 70 mph (on speedo), i am around 2700 rpm. Same setup as you...3.08 diffs, 6.5TD, 4l80e
Edit. That is on flat roads.

 

[01GRANDER]

For reference, at 70 mph (on speedo), i am around 2700 rpm. Same setup as you...3.08 diffs, 6.5TD, 4l80e
Edit. That is on flat roads.

Any ideas on where I’d need to start? Someone said brake switch but I’m confused how that would help top speeds, I assumed when you pressed the brake to decelerate, it would unlock but it’s not as if you press your brakes while accelerating so I would think default position(not activated) wouldn’t help lock it.

 

[01GRANDER]

What differential gears are you running. You have a late model so you certainly don’t have 2.56. If you’re running 3 or higher then you will drive more slowly at a higher ROM.

I think 3.08 but other 1152’s can do 70 on lower rpm’s.

 

[01GRANDER]

It wont give a code if you are in the wrong gear. Could the shifter linkage be messed up?

I feel it shift 3 times so I’d assume it’s going through all 4 gears. I don’t really know about the lockup, I’ve been driving a cvt vehicle for so long or a manual before that.

 

[Action]

I feel it shift 3 times so I’d assume it’s going through all 4 gears. I don’t really know about the lockup, I’ve been driving a cvt vehicle for so long or a manual before that.

I could feel “shifts” at 10, 20, 30, and 40 mph. So i guess the 40 was torque converter.
if i was cruising down the road with throttle held, and pushed slightly on brake pedal, the rpm would go up. I think this is a test of torque converter.
Have someone drive behind you and see if your brake lights are on while the high rpm is happening. It could be as simple as a brake switch adjustment. Or maybe unplug the converter half of the brake switch and test drive it?

 

[01GRANDER]

I could feel “shifts” at 10, 20, 30, and 40 mph. So i guess the 40 was torque converter.
if i was cruising down the road with throttle held, and pushed slightly on brake pedal, the rpm would go up. I think this is a test of torque converter.
Have someone drive behind you and see if your brake lights are on while the high rpm is happening. It could be as simple as a brake switch adjustment. Or maybe unplug the converter half of the brake switch and test drive it?

Excuse my ignorance but what would unplugging the converter half do or test? Sorry, just trying to learn.

 

[Action]

Excuse my ignorance but what would unplugging the converter half do or test? Sorry, just trying to learn.

I dont know if that switch is normally open or closed. If the switch is out of adjustment or bad, it would cause higher rpm with torque converter not doing what it should. It is mentioned in one of the troubleshooting manuals.

 

[98G]

Excuse my ignorance but what would unplugging the converter half do or test? Sorry, just trying to learn.

It would remove one possible cause of converter unlock.