Bad milage not able to get more than 9 miles to gallon truck has 460 cu. in. engine with auto trans and 410 rear gear only turns 2500 rpm at 70 mph

you might have to have your transmission downloaded.you have to go to a kia dealer\'put it on a machine.if the code is out it will make your trans mission jerk.cost me $400 dollars.in my 2006 kia spectra ex

check the moter mounts..

I’m happy to help further over the phone at https://www.6ya.com/expert/jovani_c02b023fe087f6cd

change trans fluid and filter and a fuel filter might not hert

I don't think you can get a rear end that high sped, the best I've ever seen is a 3.2 something . I had that with a 305 and my engine revved higher than 2200 with that. I think you would be better off with a 700R4 transmission from the early-mid 80's. It should bolt on and the overdrive works off an electric/vaccuum switch mounted on the firewall. Hope this helps.

Hi

It does look like you have a 3 speed C6, if the PRND21 description is correct. If you do have overdrive, the "D" will be printed in a white oval.

Sounds like it is OK. My Mustang has a 351C with a C6 trans, and 3000 rpm is about right at 70mph.

The defining factor on the rpm will be the Differential gears, which in a truck, might very well be taller gears instead of highway gears, as the taller gears provide more power output at the axles than the highway gears do.

Example:
if you had 3.0 to 1 gears (Highway), that means that the driveshaft will turn 3 times for every complete revolution of the rear wheels(Axle)

If you had 4.0 to 1 gears, then the driveshaft would turn 4 times for every revolution if the axle. Lots of torque for pulling stumps, but on the highway. the engine will have to turn more rpm's to maintain 70 mph vs a 3 to 1.

with the 3 to 1, you will turn less rpm's on the highway, but will have less available low speed power (Torque) at the wheels.

Sounds like the truck is doing fine.

What you have is the torque converter clutch,cycling on and off.
When it is off.your rpm will go up and your milage will go down
First-check to see if your brake switch, on the back of the brake peddle, is loose or misadjusted. When you apply the brakes,the first thing to happen, is that you unlock the converter,so your trans is not connected directly to the motor,or you would stall. Then below 42 MPH,your trans is working off the converter, as a pressure multiplier ,based on rpm
Second- switch okey. You remove trans pan and change TCC Solenoid.

Let me know if if you need more guidance

I would leave the gear ratio you have in there. If you go to a 4:11:1 ratio you are going to be turning higher rpms which means more air/fuel mixture being burnt. If you go lower say 3:55:1 you will loose your pulling power.

Replace transmission.

if the hydraylic torque converter or trans is low on fluld then the bands and servos will not accuate the gears properly

You should have another gear "5th" at 70mph your tacho should read about 2500 rpm.
Make sure you don't need to depress something or push the gear stick against a spring to select 5th.
Is there a gear layout on top of the gearstick knob, do you have 5th gear on there?
The highest gear ratio is a little over 1 to 1 so at 70 mph you would expect 3500 rpm, but, it is a little over 1 to 1 so it will be closer to 2500rpm.