Gearing problems
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Joined: Jul 2013
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Gearing problems
I need some help!!!. I have a 1978 f150 with a 400 with the c6. The plate on rear end says it has 3.55 gears. When the truck is in 4th gear at 35 mph the truck is redlined. Cant use first gear it is way to low. Can start out in 3rd or 4th gear no problem. The truck was used as a plow truck before i bought it. I need help figuring out what could make the truck be geared so low
Post Fiend
Joined: Mar 2011
Posts: 8,501
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From: Lynchburg, VA
Is this an automatic or a manual? C6 only has 3 gears and can't be manually shifted. Sounds like you have a 4 speed manual tranny (NP435) with granny gear first.
How do you know it's 'red lining'? Do you have a tach hooked up? What RPM is it running?
How do you know it's 'red lining'? Do you have a tach hooked up? What RPM is it running?
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The truck is not a c6 that was a different truck that i have it is a four speed. Not stuck in low range
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Cargo Master
Joined: Jul 2005
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From: Kansas
if you can easily start out in fourth gear and it is not in low range, then you've got some really low gears in the rear...how are you determining "redline". If you have a tach, let us know exactly what your speed is and what RPM you are running in fourth gear.
Elder User
Joined: Feb 2011
Posts: 633
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From: Grande Prairie, Alberta
What kind of rear diff does it have? Pull the cover and check the gears, if it's a 9" pull the carrier, a bit tougher but better than guessing.
Does it drive ok in 4wd of are the diffs binding. If it drives ok then the front and rear must be geared close, pull the front diff cover.
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