loaded up a rock crawler about 5500 lbs onto a 20' trailer about about 2000 lbs and a TON of gear, im figuring about 8000 total trailer weight.

In short,,, the truck did great I could go up passes with no problem at all, it did its share of shifting but i could go as fast as i wanted up any hill depending on where i wanted to hold the rpms at. Impressed with the the power of the ole classic big block..

I did mileage checks the whole way by stopping frequently and refilling the tank. I started out at sea level (bay area) and my destination elevation was about 6000 ft (sierra's).

The truck, 01 2500 HD 4dr longbed 4.10's 295-70-17 with a leveling kit.

Here in cali you cant tow over 55mph, although a lot do along with myself (sometimes) this brought on the only problem which to me was a big one. At 55mph in 5th gear the truck is below 2000rpm and is constantly hunting between 4th and 5th gear. If there was a way to keep this thing in 4th I would be a happy camper. Even at 65mph the truck is at 2k and can barely hold that gear and would often shift down to 4th and rev about 3k and would do just fine until is would shift into 5th,,, back and forth even in tow haul mode kinda drove me nuts and would be my only gripe.

Now, back to the question you all have been waiting for,,,, MILEAGE,,, yeah well,,, let me put it to you this way,,,, to make myself feel beter i'm never going to check milagae again i'm just going to fill it when i need to fill it and call it good.

most of the driving was freeway and I got about 7.5 to 8 at best. the last 60 miles was steep climb, 7% grade part of the way and lots of switch backs, that equaled a,,,, (are you stilling down?) 5mpg. Again i figured this by filling the tank prior to heading up the 60 mile climb and then filling when I got to the top, thats about as accurate as i could get and to be honest i was running the truck hard, wasnt being conservative by any means.

A buddy had a 6.0 PSD towing 11k and used more fuel than me but was definatley towing more and did very well,, not sure how my truck would have handled that. Another guy has a lifted PDS programer exhaust the whole 9 yards, I stayed with him on every hill without a problem or over reving my engine the only issue was being covered in all that BLACK smoke.

All in all,,, i'm pleased, even with the shit milage, my load was very tall off the trailer, i would have to say,,, probaly as tall as a fith wheel, not very aero dynamic.

My only issue is not being able to keep it in 4th gear, if going 55 to 65 mph it gets annoying with the up and down shifting - need to figure out a way to fix that.

A ZF would keep her in 4th as long as you wanted:rolleyes:

I do agree with you though, one of my buddies has an allison and he has the same problem as you, on the rural highways that are windy you are always in that 55 mph range and its always shifting, if you find a cure let me know so I can tell him!

loaded up a rock crawler about 5500 lbs onto a 20' trailer about about 2000 lbs and a TON of gear, im figuring about 8000 total trailer weight.

In short,,, the truck did great I could go up passes with no problem at all, it did its share of shifting but i could go as fast as i wanted up any hill depending on where i wanted to hold the rpms at. Impressed with the the power of the ole classic big block..

I did mileage checks the whole way by stopping frequently and refilling the tank. I started out at sea level (bay area) and my destination elevation was about 6000 ft (sierra's).

The truck, 01 2500 HD 4dr longbed 4.10's 295-70-17 with a leveling kit.

Here in cali you cant tow over 55mph, although a lot do along with myself (sometimes) this brought on the only problem which to me was a big one. At 55mph in 5th gear the truck is below 2000rpm and is constantly hunting between 4th and 5th gear. If there was a way to keep this thing in 4th I would be a happy camper. Even at 65mph the truck is at 2k and can barely hold that gear and would often shift down to 4th and rev about 3k and would do just fine until is would shift into 5th,,, back and forth even in tow haul mode kinda drove me nuts and would be my only gripe.

Now, back to the question you all have been waiting for,,,, MILEAGE,,, yeah well,,, let me put it to you this way,,,, to make myself feel beter i'm never going to check milagae again i'm just going to fill it when i need to fill it and call it good.

most of the driving was freeway and I got about 7.5 to 8 at best. the last 60 miles was steep climb, 7% grade part of the way and lots of switch backs, that equaled a,,,, (are you stilling down?) 5mpg. Again i figured this by filling the tank prior to heading up the 60 mile climb and then filling when I got to the top, thats about as accurate as i could get and to be honest i was running the truck hard, wasnt being conservative by any means.

A buddy had a 6.0 PSD towing 11k and used more fuel than me but was definatley towing more and did very well,, not sure how my truck would have handled that. Another guy has a lifted PDS programer exhaust the whole 9 yards, I stayed with him on every hill without a problem or over reving my engine the only issue was being covered in all that BLACK smoke.

All in all,,, i'm pleased, even with the shit milage, my load was very tall off the trailer, i would have to say,,, probaly as tall as a fith wheel, not very aero dynamic.

My only issue is not being able to keep it in 4th gear, if going 55 to 65 mph it gets annoying with the up and down shifting - need to figure out a way to fix that.

http://www.kennedydiesel.com/docs/Allison%20OD%20lockout%20final.htm

thats all i can find,, looks involved

http://www.kennedydiesel.com/docs/Allison%20OD%20lockout%20final.htm

thats all i can find,, looks involved

I just skimmed over that product, but do you think that would even work with the 8.1, or is it just for the dmax?

I just skimmed over that product, but do you think that would even work with the 8.1, or is it just for the dmax?


i was wondering the same thing, not sure.

It works with the Allison 1000 regardless of engine. GM is the one who came up with this as a TSB and sells a factory appearing switch that installs in the dash cubby hole. Those instructions are based on the GM TSB (technical service buliten). I have one of the GM switch kits but haven't installed it yet, like most of my stuff.

Vernon

It works with the Allison 1000 regardless of engine. GM is the one who came up with this as a TSB and sells a factory appearing switch that installs in the dash cubby hole. Those instructions are based on the GM TSB (technical service buliten). I have one of the GM switch kits but haven't installed it yet, like most of my stuff.

Vernon



where did you get it? how much was it?

Do you have a GM part number for the switch kit?

It works with the Allison 1000 regardless of engine. GM is the one who came up with this as a TSB and sells a factory appearing switch that installs in the dash cubby hole. Those instructions are based on the GM TSB (technical service buliten). I have one of the GM switch kits but haven't installed it yet, like most of my stuff.

Vernon

I got mine from another board member (ABQ Firefighter) who quickly built up a really nice 8.1 Silverado then just as quickly decontented it, sold the upgrades, and bought a Cummins Dodge.

Ok guys finding this stuff on the net is difficult so send beer money :). I can't just cut and paste my pay for view internet information sites pages for you. But usually, if I look hard enough, I'll find it somewhere else free like the belt routing from the other day.
After clicking on this link scroll down just about half-way until you reach Bulletin No. 02-07-30-051. It is the one that addresses the problem and GM's fix by installing the O/D lockout switch and reflashing the TCM to accept it. The TSB has all the part numbers. I last checked on them about 2 years ago and it would run about $100 for the switch kit (I'm not real sure on this so call).
http://www.diesel-central.com/Tech/GM-TSB/Service%20Bulleti1.doc

Here's some pics of mine:
http://i212.photobucket.com/albums/cc31/VCradier/ODswitch001.jpg
http://i212.photobucket.com/albums/cc31/VCradier/ODswitch002.jpg

Vernon

manic,, thats awesom info thanks... where does that new switch mount?

It mounts in place of the cubby hole in the center of the below the radio and A/C vents. You will loose the cubby. The trucks that have a pass. airbag off switch located there will have a removable blank in the switch plate that the new O/D inhibit switch will replace perfectly.

Also, when reading the TSB note that the Vortec 8100 is the L18 gas engine mentioned.

Vernon

ok cool, thanks,, so i heard that their is a kit from GM thats is a plug in kit, from what you posted that doesnt seem to be the case it sounds like there will difinately be some wire splicing going on.