RPMs too high! MPG too low.....

[GlennReaIdaho]

I have a 1997 international DT 466E with an Allison transmission automatic. I want to use this vehicle to deliver campers however at 63 miles an hour pushing 2300 RPMs and only getting 8.9 miles per gallon.

My questions are is this transmission that came with this truck programmable? is there really a sixth gear? Does anybody know of a overdrive unit that can bolt behind the transmission?

Would it be worth it to buy a new “pumpkin” and change out the gears?

I guess if I have to I would put a manual transmission in but I really want to keep this Allison automatic or one like it......

I’m guessing if I can lower the RPMs the MPG’s would rise.

By the way I’m guessing there’s some kind a governor on this truck or something because the cruise control won’t set any higher than 63 probably a good idea anyway:

Thanx:

Glenn

[Mountain Gnome]

Originally Posted by GlennReaIdaho

I have a 1997 international DT 466E with an Allison transmission automatic. I want to use this vehicle to deliver campers however at 63 miles an hour pushing 2300 RPMs and only getting 8.9 miles per gallon.

My questions are is this transmission that came with this truck programmable? is there really a sixth gear? Does anybody know of a overdrive unit that can bolt behind the transmission?

Would it be worth it to buy a new “pumpkin” and change out the gears?

I guess if I have to I would put a manual transmission in but I really want to keep this Allison automatic or one like it......

I’m guessing if I can lower the RPMs the MPG’s would rise.

By the way I’m guessing there’s some kind a governor on this truck or something because the cruise control won’t set any higher than 63 probably a good idea anyway:

Thanx:

Glenn

You need to find out WHICH Allison tranny you have. Likely the AT545. It does not have a lockdown tranny. It does not have overdrive or 6th gear.


If you do have the tranny with 6th gear, then yes, replace the gears in your "pumpkin". There is also a tutorial thread here on "onlocking " the 6th gear.



If you are speed governed, catallackid may be able to free you.

[ol trunt]

Just curious. What do you mean by " I want to use this vehicle to deliver campers ".
Jack

[Drew Bru]

I dunno, 9 mpg doesn't sound too bad for a bus, esp. if its a full size bus. We get around 7.5 maybe 8 mpg. Not sure how much gain you can expect to get and whether it'd be worth the cost of swapping out gears to do it.

[PNW_Steve]

If it has the AT-545 you may want to keep looking for a bus with a more suitable transmission.

Hauling travel trailers down the interstate at 65 mph is likely to kill a 545 before long.

Also, be aware of length limits in various states. That will place a limit on what you can legally pull behind a bus.

You can probably get away with running a little over length pulling your own trailer but delivering for a manufacturer, they will insist that you run legal.

[GlennReaIdaho]

Originally Posted by Mountain Gnome

You need to find out WHICH Allison tranny you have. Likely the AT545. It does not have a lockdown tranny. It does not have overdrive or 6th gear.


If you do have the tranny with 6th gear, then yes, replace the gears in your "pumpkin". There is also a tutorial thread here on "onlocking " the 6th gear.



If you are speed governed, catallackid may be able to free you.

I’m guessing you’re right but this is an at545 I intend to go to international with the Vin numbers. This is a cab and chassis truck it is not a school bus
I will try to find the thread about same. Thanks for the info on unlocking the governor although I don’t think it will make much difference since at 70 miles an hour the RPMs are maxed

[GlennReaIdaho]

I guess I should’ve mentioned that this is not a bus it is a cab and chassis truck

[GlennReaIdaho]

I should let you guys know that this is a 4700 truck and cab and chassis

[GlennReaIdaho]

This vehicle is a cab and chassis I deliver gooseneck and bumper pole recreational vehicle for a living

[PNW_Steve]

Does it have a push-button shifter?

If so, it is probably an MD-3060. That would be FAR better suited to your application.

[GlennReaIdaho]

Originally Posted by PNW_Steve

Does it have a push-button shifter?

If so, it is probably an MD-3060. That would be FAR better suited to your application.

No sir it is not the push button has a lever

[EastCoastCB]

Originally Posted by Mountain Gnome

You need to find out WHICH Allison tranny you have. Likely the AT545. It does not have a lockdown tranny. It does not have overdrive or 6th gear.


If you do have the tranny with 6th gear, then yes, replace the gears in your "pumpkin". There is also a tutorial thread here on "onlocking " the 6th gear.



If you are speed governed, catallackid may be able to free you.

A 545 has 4 forward gears.

[cadillackid]

your MPG and RPMs are about right.. your valve cover will tell you what spec 466E you have... the trans is likely MT643 or AT545.. a picture of the transmission would tell us what you have..

[concrete]

Do you have 5 forward speeds now? Does your shifter indicate 1-2-3-4-D? or 1-2-3-D?
If it’s the former and you have 5 speeds it’s probably the Md3060 tranny which IS 6 speed capable. You will NOT be able to work through the IH dealer to unlock 6th, but there are options for the persistent Contact the member “bapos” for the contact info of an Allison guru. Also check out the Allison 6 gear unlock tutorial; it’s very long with a lot of info, most of it true😄. If you’re in a hurry skip to the last couple pages and find the posts by bapos. You may also need to bump up the hp for the taller gear, especially if you have mountains in your future. I have heard of a reflash for the computer to give a little more power, but not a lot.

[NavyVet]

Diesel Engine head pressure has alot to do with that.
Im getting mine checked in a couple weeks.
5.9 Cummins with and allison os what i run.
Get a diesel mechanic to check that first.

A lot cheaper than changing the other stuff.
Jist a thought

[banman]

Originally Posted by cadillackid

your MPG and RPMs are about right.. your valve cover will tell you what spec 466E you have... the trans is likely MT643 or AT545.. a picture of the transmission would tell us what you have..

As said above.

The 643 is a HD 4sp auto with lockup converter -- I'd say this is the minimum you'd want for your intended purpose.

The 545 has no lockup so will be making more heat & less mpg...
Neither of these trannys have any o/d to unlock.

The MD3060 came behind your engine so the parts exist but that's a serious project although long term and if you're driving enough could be worth it.

[oleman]

For some unknown reason many folks tend to exaggerate their fuel mileage.

We just made a trip from Pueblo Co to Key west FL in our 36 foot Cummins all mechanical 300 HP 8.3 powered motor home. Towing a JEEP TJ, it got 9 MPG without the Jeep and 8 MPG with the Jeep at the local speed limit for the drive. We parked the RV and took the Jeep out to Key West. Was a great and long planned trip. We operated at least one class 8 truck for years, powered by Cummins, or Cat or Detroit, Was a lucky trip when we got 6 MPG with a load. Once we did a heavy haul with a 500 HP Detroit, did around 1 MPG from Norfolk to Seattle. OUCH