allison transmission question

[dzlnut]

Hey guys,


I am looking at a buying a dump truck that has an allison 750drd automatic
The truck would be used locally in the mountains with freeway (100-150 miles each way) and offroad use.

I am having a hard time finding the specs on this transmission.

How many gears does it have?

How does well would this transmission perform?

thanks

 

[markshr151]

Automatics have a bad rap because we all have cursed our autos in our one-ton trucks but what if your skid steer had to be shifted five times to pick up or Carry a load. Many years ago I replaced a 5x4 ( witch I knew how to shift ) with a 5 speed Allison the result was like adding 100 hp. On top of that in the sand my little tandem dump truck with 18 yds was now passing the Mack's in forward and reverse. I also got good service and economy. When I sold the truck I told the new owner/not driver that the trans was fool proof but not jerk/idiot proof, he proved me right when the driver returning to the pit down shifted into first at 60 mph and broke more stuff then the truck was worth. P.S. I live in flat country.

 

[dzlnut]

thanks Mark for the info.

Does anyone have mountain experience with driving a similar rig?

It has a big cam cummins 400

How well would the jake brake work with this transmission?

 

[markshr151]

I think they work better because they spend less time between gears and I have driven both. P.S. I live in flat country.

 

[koldsteele]

Not real sure about your particuliar application but my experience Allison PTO 's are a differnt animal then a manual trans. ...

I mounted a feed wagon on truck with an Allison in it and when loaded the PTO would not turn at idle you had give the motor rpms to get it turn ...Basicily you stall the converter ...Just something to think about in a dump application ..They are a little different to get along with when putting a PTO on one ..

 

[CM1995]

Not real sure about your particuliar application but my experience Allison PTO 's are a differnt animal then a manual trans. ...

I mounted a feed wagon on truck with an Allison in it and when loaded the PTO would not turn at idle you had give the motor rpms to get it turn ...Basicily you stall the converter ...Just something to think about in a dump application ..They are a little different to get along with when putting a PTO on one ..

I have had a couple in dump and roll-off applications (400HP, 4500RDS 6sp, Jake) and the PTO performed well for both types of trucks.

However, Koldsteele I know what you mean with using an auto for different PTO applications. Rented an auto F750 2,000 gal water truck and sent it back the first day for the same reasons - the truck wouldn't spray any distance at idle and had to keep it rev'd up. Swapped it for a F750 with a 7sp.

On the topic of Jakes and autos - if the truck already has one then you will know how the Jake integrates with the auto. If you are planning on adding a Jake just keep in mind that you will probably have to integrate it (best word I could think of) with the Allison.

 

[dzlnut]

It has a jake brake already in it but was disconnected
when the original auto trans was replaced with the current one

how do you integrate the jake with trans?

 

[CM1995]

how do you integrate the jake with trans?

That's a question beyond my pay-grade..:cool2

My first Allison was in an '04 International 7600 with a C13, it didn't have a "jake brake", so part of the purchase was that the dealer sent it to Cat to have an exhaust brake put on it. Had to send the truck back a few times to the Allison shop to calibrate (probably a better term) the Allison shift pattern to the exhaust brake. The "Jake" would kick in and the Allison would downshift abruptly.

I'm not a mechanic, so I don't know the inner workings of it, but after a couple of visits we got it where we wanted it to be. I know it's not a good explanation, maybe someone with more knowledgable of the inner workings can explain it better.

 

[dzlnut]

it sounds like they adjusted the valve body of the tranny to change the shift pattern...

the truck is still for sale I am thinking about buying it but it concerns me that the jakes are disconnected.

Also can this tranny take the abuse of 80K lb gross weight in the mountains?

I will be driving back & forth from 1000ft to 7500ft elevation

 

[M_T_Noggin]

I used to own a KW with a 3406, HT 750 DRD, 4 sp Spicer Aux, 58000 Lb rear ends. Transmission performed very well. Truck was used off highway 90%. It had a built in retarder. With retarder it needs a very large engine cooling system as it cools the transmission oil which gets very warm with the retarder. With the DRD reduction and Aux you could start on any grade with any load. Fuel consumption was terrible compared to conventional trans. 80000 lbs was a light load and I used it moving logging equipment in steep terain. A D8 was a very easy load. Trans had a lockup switch to keep it out of converter.

 

[dzlnut]

thanks M_T_Noggin for the info

how was the fuel consumption on the hwy?

Ill have to find out if this truck has a transmission retarder

The truck I am looking at is a 1986 Western Star with a Big Cam 400 cummins what kind of MPG can I expect?

 

[M_T_Noggin]

I never did any kind of MPG figures as most of the hauling was off road. When it was on the highway, being low geared it was wound up most of the time. I remember moving Cat and Hitachi Excavators (Roadbuilder versions), and you could just about watch the fuel guage drop. I don't know how much they weighed, but with all the quarding and buckets they were a slow grind up the mountain. The Allison had six speeds, you had to be stopped to put it in first as it was a huge difference from 2. You could put the control in 6th, and it would shift on its own from 2-6, or you could manually shift it. The shift from 3-4 was very severe, and the dealer could never improve it, so it stayed that way with no ill affects. The aux had be changed when the truck was not moving. It was a very tough transmission and I think it saved the rear ends. With standard trans and a clutch it would have been very hard to start moving on a steep grade with the loads it
moved. I have a picture somewhere of moving a fully rigged grapple yarder, will try and did it up.