old 3 speed with overdrive transmission vs newer 6 speed

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Active member
Jul 22, 2012
Hello all,
I have a 1997 v10 with three speed automatic and have been wondering if the newer trucks with 6 speed or whatever transmissions get much better gas mileage.
I know they ride nicer but didn't know if the cost of a new truck would be worth it or not. I think probably not but thought I'd ask.



Well-known member
Jun 7, 2015
Wenatchee, WA The hot side of the state
I'm talking motorhomes here, so take it for what you want. We had a 1998 Thor 31 footer V10, 3 spd w/overdrive. It got 7.5 - 8 mpg with the driving we do over mountain passes and driving freeways. On slower 55 -60 mph flatter ground, up to about 8.8 mpg. Our 2016 Thor 31 footer, V10, 6 spd is getting nearly the same identical numbers. I like the quick shifting on acceleration of the 6 spd, but not how it down shifts when going slow on back roads heading down hill.


Well-known member
Sep 19, 2018
Assuming your 1997 truck is paid for and not costing an extreme amount in repairs, any gas mileage increase will be more than offset by the high cost of newer V10 trucks. You can buy a lot of fill ups with 40 to 50 thousand dollars.

On the other hand, if you strongly want a newer TV with lots more features and more comfortable ride, then it may be worth the high cost to you to get a newer TV. I'm reading great things about the 2019 Ram pickups. Wish Santa would leave one on my lawn this Christmas.  ::)  ::) ::)

Gary RV_Wizard

Site Team
Feb 2, 2005
West Palm Beach, FL
Isn't the tranny in your 1997 the E4OD, meaning it is a 4-speed (3+ Overdrive)? I ask because the newer 6-speeds include OD in the "6", so yours isn't quite as far behind as you may think.

When you are cruising the highways, the truck will generally be in its top gear (overdrive) and that will be a pretty much identical gear ratio whether the tranny is 3-speed, 4-speed or 6-speed.  The exact gear ratio in the top gear varies a bit with the rear axle gearing, tires size and engine torque/hp, but all other things being equal the final drive ratio will be the same.  The advantage of more gears is better power application between standing starts and cruise speed, e.g. acceleration and hill climbing.  You gain a little mpg around town and on long grades because a more optimal forward gear will be auto-selected, but for most owners that is not a large factor in overall mileage.

Most 6-speeds (or the newer 8 or 10 speeds) have multiple overdrive gears, so have more choices that still produce better mpg. Your E4OD kicks out of overdrive at the slightest load and goes to 3rd. On any sort of grade, it probably hits 2nd gear, which is a substantially different ratio and really hurts the mpg. A 6-speed can hang in and use 5th or 4th or 3rd in that same range, and only resorts to 2nd gear when the going gets rally tough. That can help mpg quite a bit in those circumstances. If you do a lot of driving in rolling hills, you will notice the difference in both economy and perfromance.

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