Allison Transmission

[Traveler II]

Question for those that have the Allison transmission, when pulling to you keep it in “D” or do you use the “M”? I’ve been leaving it in D and pulling at 60 mph get about 11 mpg. A guy was telling me he uses “M” and keeps it in 5th gear and is getting 14 mpg with a rig that is bigger than ours. I was just wondering if others have seen improvements in their milages?

[Jash]

I have been pulling just as you do, in Drive tow haul mode, I also get 11 mpg. When not towing around town Im seeing about 15. The only issue I see is you loose the benefits of the tow haul mode in M.

[Mike Clay]

If your in tow mode and under 65 mph you are in 5th gear with the 6 speed Allisons. The only time I use manuel is going down hills I would rather choose when it shifts down.

[rlhedlund]

When hauling trailer (33TS), I leave it in D in tow mode and get 10 mpg. Best I get with no trailer is 16 mpg in D.

I find it hard to believe 14 mpg when hauling a big trailer in manual. I may give it a shot just to see. I have heard Cummins getting that much, but not Duramax/Allison.

[Mike Clay]

MPG is something you hear that seem to be all over the board and most is fiction. I have gotten as high as 14 mpg going through Salt Lake but most of the time I average 11 - 12 mpg while towing. Leave it in drive you dont need to be shifting with the button plus doing so adds more heat to the tranny. With my edge insight I can watch (if i want to) when the torque converter locks how much slip it has what the true tranny temp is and so on. When I am board and running empty I sometime use the m mode and shift with the buttons. The tranny temp does rise not to a danger zone but it does go up 50 or so degrees. I am willing to bet you will not get better mileage by using the M mode. Another thing DO NOT shift it to 1st while still moving bad ju ju

[Traveler II]

I figure that Allison is far smarter than I am so I think I will keep trucking like I’ve been trucking.

Thanks for the input.

[stevesmith]

Not a chevy guy here but it has been my experience that people who claim higher than normal MPG usually are stating an average MPG on a truck they use daily just driving around vs. a pulling MPG where the TV is under load the entire time. I average about 13 or 14 MPG as well but thats and average of running empty at about 16 or 17 and pulling the camper at about 9 or 10.

[Rob & Cathy]

and pulling the camper at about 9 or 10.

That's what I got too when I had my '97 7.3 F250.

Rob

[stevesmith]

and pulling the camper at about 9 or 10.

That's what I got too when I had my '97 7.3 F250.

Rob

What are you getting with the '05?

[surveyman]

It's good to hear that all the Allison guys are getting about the same. Driving to work (18 miles) and just around my mileage is about 15.5. Plus or minus 0.5 depending on weather, it was worse in the winter. Towing mileage is 9.5 to 11 depending on the wind. That is towing in D and at 68 with tow mode on. As Mike said it doesn't shift into 6th until 65 and it just seems to tow the best at 68 or more, although for most roads that is plenty fast for me. I do agree that the tranny stays cooler when using tow mode.
This weekend I plan to change the oil and filter in the tranny. A guy said I should go to synthetic tranny oil but I'm going to stay with Drexton VI and the AC Del co oil filter, got to look in the manual to make sure that's what it calls for. Learned my lesson when I used a Fram fuel filter. The fuel censer started leaking and the dealer said he could not replace it under warranty because I attached it to the Fram. $365 later I had my truck back. Now it's out of warranty but going to stay factory all the way.

[Rob & Cathy]

and pulling the camper at about 9 or 10.

That's what I got too when I had my '97 7.3 F250.

Rob

What are you getting with the '05?

7-8 towing.

Rob

[Olbird]

I get about 10.5 MPG with the transmission in tow mode, about 14 .5 - 15.5 MPG with out pulling.
My engine does not like low RPM's when pulling.

[campswithcritters]

When you get the bigger allisons most do not have a tow mode, but you do select the top gear. I find mine gets about .5 mpg better keeping it in 5th below 62 mph. Of course with a 8.3 liter my RPM at that speed is 1700 in 5th or 1400 in 6th. Sweet spot for that motor is 1800 so if in rolling hills I run 65 mph in 5th and 6th on the flats. In the duramax Allison combo I always found the tow mode got better mileage and performed better than me trying to control it, and I had several years of a 6 speed manual before that.

[CaptainSkidmark]

I'm just here curious guys. Is your milage that you are saying from a cold motor or from one that is already warmed up. My Ram's milage sucks until it warms up so I usually will let it idle until it warms up.

[Mike Clay]

Well you should always have some heat in a diesel engine but you should not let them idle for extended periods of time, if you have an exhaust brake turn it on to warm up your engine. Before I tow I try to either go get fuel or run an errand before towing.