Community Forums

Cummins8.3 · 03-27-2011, 07:33 PM

Mike: It wasn't running the high rpms before. I'm not sure that the RPMS were at 60mph but sure they werent so high. The engine is screaming.....

Gear Head: my kickdown cable is in the picture. I can rotate the unit with my hand. I also posted where it connects to. You can see a cable thats disconnected in the 3rd picture, I am pretty sure its my cruise control.

gear-head · 03-27-2011, 07:48 PM

in the pic i attach see the yellow circles can you move this cable freely

Cummins8.3 · 03-27-2011, 08:23 PM

Gear Head: It pushes freely when I push on the end where the arrow is. I can also hear it moving on the side of the transmission.

Thanks.....

Cummins8.3 · 03-27-2011, 08:29 PM

Just a thought:

is there anything else that can cause the Engine to have High Rpms but the Output to the Transmission be low?

If so maybe the transmission is ok but the engine has an issue.

My thought is: if the RPMS are high then the Flywheel must be turning faster.

But; if there was something that can cause high rpms and a slow flywheel then the engine would be my issue.

I am running out of options and this scenario came to mind.

Mike Canter · 03-28-2011, 07:35 AM

The answer to your previous post is NO but having said that everything sure points to the converter being bad. Maybe just failing to lockup. If not locked up then it also has a high percent slip. My using that software I pointed to it shows that it cannot be just stuck in third gear. The only way it could be stuck in third gear and not compute is the unknow slippage in the torque converter. I believe you said that you can feel it shift three times from a standstill and see the tach swing with the shift, is that correct?

Cummins8.3 · 03-28-2011, 10:24 AM

Yes, I can feel it shift 3 times. But when I hit 3rd gear the tach drop twice, once when its shifts and the next time must be the torque converter lock.

Then it shifts to 4th gear, but the tach only drops once, I dont get the second drop in RPMs like I do in 3rd gear.

The RPMs seem high right from 1st gear.

Mike Canter · 03-28-2011, 10:54 AM

Think it is time to take it into a certified Allison repair shop.

hometool · 03-28-2011, 11:02 AM

hi jmho i would very closly ck the operation of the kick down linkage i own an older car that when it sits idle the kick down sticks in wot position resulting in much higher revs befor up shifts and very late if any converter lockup. lee

Mike Canter · 03-28-2011, 09:18 PM

I don't think it can be the kickdown cable if it is shifts three times under normal acceleration and shifts into fourth. I don't see how if it shifts into fourth gear how the kickdown cable sticking will make the revs high. If the kickdown cable was stuck then it would wind out each gear to the max when starting from a standstill but would still shift into fourth when the rpm got high enough and the rpm would then drop. Then if you slowed down a little the tranny would suddenly downshift to third until you increased rpms again then it would go back into fourth.

Cummins8.3 · 03-30-2011, 09:09 PM

sorry, I didnt have e-mail reply turned on and didn't know I had replies to message.

The rpms are very high right from the Get Go. I am going to take it out tomorrow to feel for it shifting all 4 gears and also how it downshifts based on what you are saying the kickdown cable could cause.

It did sit for a couple of year besides pulling it from the front yard to backyard.

Cummins8.3 · 03-31-2011, 06:58 PM

Hey guys, I think this is good news. I tested the RPMs with my handhled Digital Tach with the Peddle to the Floor ( govened RPMs ). The Dash Tach reads 3000. The handheld is reading 2550.........So the higher the RPMs the more the dashboard tach is inaccurate. At Idle (800rpms), 1200, & 1500 rpms, the dashboard tach matches the Laser tach. Not sure why it's so far off at higher rpms unless alternator has an issue?

I have 2 diesel leaks I thought the High RPMs caused. Apparently it's a coincidence, I hope anyway. I will post pics of leaks in a new post under the correct topic.

allisontec · 04-05-2011, 07:27 PM

Cracked lock up pistons were very common in these models.

Perry White · 04-06-2011, 02:07 PM

2550 RPM from Crankshaft. Cam shaft runs at half that speed but you can't get to it.

Forty1974 · 04-06-2011, 02:12 PM

I have a 1992 coachman sportscoach with cummins 5.9 190 hp at 60 I'm at 2500 Rpm I just recently purchase it so I thought that was normal for the Allison four speed trans. am I over revving the engine thanks in advance