Help Needed Tranny going bad ?

[blkF250]

Hello 1st time diesel owner, 8th Ford truck.
I just bought a used 2004 F250 lariat 4x4, supercab sb, 93k miles.
Auto 4spd transmission. 6.0 diesel. I replaced the auto hubs with
Warn manual hubs.
Codes show a faulty speed sensor on the abs system and a glowplug issue on
Cylinder 8.
I am in south Florida so there are no hills to speak of.
When I have cruise control set at 60 mph, my overhead console
Says I am getting 19.7 mpg. I hand calculated to verify the
Numbers. When I get on the turnpike & set cruise control
To 70 mph, my mileage reading drops to any where from 13.4 to 15.2 mpg.
There are no tranny codes coming up. Some shifts when slowing down are
Hard only twice when accelerating to pass a big rig, the tranny jumped between 3rd and OD back & forth about 5 times under heavy acceleration.
When I backed off it stopped. This has only happened twice & I cannot duplicate it, YET.
Rpm is 2100 at 70, 1500 at 60.
Torque converter going bad? Why is the mileage so horrible
& all over the place at 70 & just fine at 60 & below.
Any ideas, help or solutions are highly appreciated!!!

 

[strokepower]

im pretty sure your trans is a torqshift 5R110 5 speed.... 19.7 is impressive but from my experence 13-15 is about right... i don't think there is anything weird about the difference in mileage.. just that 70 means more go pedal and more go pedal means lower mpgs... check with ford on the faulty sensor and glow plug issue you might still be covered under 100,000 miles.... i don't know much about it jumping back and forth like that.. hopefully it was nothing major.. you might wanna ask ford about that also.... good luck!!!



ps... welcome!!!

 

[blkF250]

Thanks for the reply.
Yes you are right I have the 5R110 transmission.
Turns out the torque converter was slipping like crazy
Over 60 mph. Hence the higher rpm's & gas mileage issue.
New torque converter from Ford, rpm's are down & I am getting
About 16.5 to 17 mpg at 70. Not great but better than the low
Of 13.2 I was getting before.