axle ratio

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Oct 22, 2000 | 12:02 AM

Jack_Whittle

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Joined: Feb 2000

Posts: 11

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axle ratio

I have a 1990 F 150 302 C-6 tranny that had a 355 rear end with 29 inch tires, running 60 MPH I would rev at 2500 RPM. I then had the rear end changed to whats suppose to be a 3.08, but I had just put on 31 X 10.50 R 15 and at 60 MPH I still rev 2500 RPM can anybody tell me what gives. I thought the rear end change would lower my revs now I'm running bigger tires slower. I sure did notice a change in the take off but the same revs and gas mileage sucks comapred to the 20 MPG I use to get before all this started.And lately it started stalling when the motor is warm while stopped at a corner.Revs at 500 RPM when stopped if it does not stall.
Can anybody help ?
Thanks in advance.

Oct 22, 2000 | 12:09 AM

PAUL_2

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Joined: Jul 1999

Posts: 3,172

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axle ratio

Jack , Try this site for gear ratios etc http://www.4lo.com . As for the stalling , check the Idle Air Bypass valve , its possible its carboned up & needs cleaning ? Good idea to clean the throttle plates as well .

Oct 22, 2000 | 08:53 AM

DannyP

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Joined: Jan 2000

Posts: 656

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From: Gravel Switch, KY

axle ratio

Jack,
How are you measuring the MPH? If you are just going by you speedo and you didn't change the speedo gears in the transmission it will show the same MPH vs RPM. You actually will have raised your MPH at a given RPM, but the speedo is getting the same old info it was always getting.

DannyP
89 F-150 4x4 former EFI I-6 now carbed 351W, Edelbrock heads,cam,intake,carb.
MSD 6A, T-18 but looking for a ZF. 3.55's.