6-71 Detroit Question

[DWest]

My farm grain truck has a 6-71 Detroit that gave me some trouble Friday with the throttle. Where the linkage is tide to the pump there is another cable that goes to the back of the Allison transmission that froze up. I disconnected that cable to see if it would work and the only change I could find was that the PTO wouldn't engage unless I shut the truck off. Is that all the cable is for? DWest

 

[abrankod]

What transmission is on the truck?

If it is an electronic Allison transmission, there is a throttle position sensor that runs to the throttle control lever linkage on the governor. It is used to sense kickdown, adjust shift points for throttle percentage and to sense 0 throttle for the shift inhibitor on the PTO switch.

The cable and throttle position switch costs approximately $250 at DDA however unless you have a NEXIQ ProLink with the Allison card, or the Allison DOC laptop program/cable, you will not be able to reset the throttle position sensor readings and you'll need to go pay for an hour at your local DDA to get them to push the 4 buttons on the stupid computer to reset the throttle learn.

If you can give some more info on the truck's transmission setup, I can probably get you some more help on your issue.


-Dan
The Truck & Bus Stop Inc.

 

[DWest]

1972 Gmc

The truck is a 1972 GMC tandom that I put a 500 bushel box on, so it's an not electronic controlled transmission. The cable has been sticky for years and made the throttle slow to repond, this made me look a little harder. DW

 

[abrankod]

On a mechanical trans, it STILL could be the kickdown/idle cable depending on the transmission. Theres just so darn many ways that companies have set up their transmission/engines that its hard to really decipher exactly what everything does unless you're there.

On a related note: If you do decide that you want a cable, your local DDA dealer should be able to set you up with one of these cables or you can even make your own pull cable to manually put the trans in a "pto enable" mode

-Dan

 

[DennyDay]

Are you sure it isn't the emergency shut down control? On a '72 its probably rusted thru, but was origionally sent up thru the floor near the shift lever as a pull out to shut off the engine.



GOD I'M GETTING OLD!



Denny

 

[chuckwilson]

NO, its the kick down cable, if you fix it, the truck will drive & shift better!!!!!!

 

[AndrewGray]

I agree. It is the kick down cable. We run a lot of those allisons. Tough buggers! You have the 543 or the 653 transmission. Replace the cable either new or from another truck and it will go. The actually will where out bad and than cause grief . Better to get a new one but in the mean time you can get by with another working one from another truck. Then just set up the length for the kick down.

 

[DWest]

I'm sure you guys are right as the truck has never really shifted like an auto should. It lugs way down before it shifts and if you've ever driven a 2 stroke detroit you know they don't lug. Will see if I can locate a new one. Also how hard would it be to turbo this motor and is there enough capacity in the injector pump to add more fuel? Thanks! DW

 

[abrankod]

Adding a turbo to a non-turbo detroit 2 cycle requires a few changes.

First off, the detroit 2 cycle doesnt actually have an "injection pump" the injectors themselves are the pump (called unitized pump. ) You'll need to get changed to higher volume ones. This should cost around $200 for a reman set of 6 injectors. I'll find out from a friend which part number you need if you wanna do this project. The gear powered fuel pump on the side of the motor is just basically to keep fuel flowing to the injectors.

Second, the throttle rise time buffer has to be adjusted to allow for turbo spool time before increasing fueling at the rack to keep it from smoking like a ******* whenever you hit the throttle. Also the governor may need to be slightly adjusted to keep the rack from hunting.

Finally, depending on your desire, you may want to intercool the turbo air prior to the blower, and aftercool the blower air prior to entering the air gallery. The 6-71T generally had neither charge air cooler on the stock configuration. It simply has the turbo feeding the blower directly.

All in all, its not a huge project, the turbo will be the most expensive part unless you can find a junkyard donor somewhere.


-Daniel

 

[DennyDay]

Well so much for that - - - sorry-I missed the Allison part of the post! Yep the few that were out there had frequent kick down cable breaks.



Denny