What gears?
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Senior User
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From: Fayetteville Arkansas
What gears?
Its time to rebuild my D44 and 9" and was looking for some advice on the right gearing for my truck. My truck is a 1977 F-150, that will be running a 408w with a C-6 tranny and im using a comp XE262 cam and have 33" tires. I would like to find a good balance between street and offroad, i am taking the NP435 out for a C-6 for better highway manners but would still like to have a capable offroad machine. Thanks for your time
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From: The Vieux Ford, Kansas
The C-6 will actually turn more rpms on the highway than the 435, both have a 1:1 top gear and the automatic will always slip some because the C-6 is nonlockup. As for gears 4:11 would be pretty good, a little low for lots of highway though. I have always liked trucks that were a little too low than ones that are a little to high.
-Johnboy
-Johnboy
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4.11s with 33 inch tires gives you 2720 rpm at 65 mph, or 24 mph per 1000 rpm.
3.91s work out to 2588 rpm at 65, 25 mph per 1000 rpm.
You can put in different numbers, tire sizes etc here:
http://www.novak-adapt.com/knowledge/gearing.htm
3.91s work out to 2588 rpm at 65, 25 mph per 1000 rpm.
You can put in different numbers, tire sizes etc here:
http://www.novak-adapt.com/knowledge/gearing.htm
Thread Starter
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Senior User
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From: Fayetteville Arkansas
Thanks for the replies, i have one more question though and excuse my naiveness i am an electrician and not a mechanic. If i kept my NP435 would i be able to spin it to my cams advertised 5,600 RPM or would i be better with a C-6
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From: Almost Heaven
I run 31 inch tires with a 4.11 gear and 4 speed auto with over drive. I keep my OD off a lot of the time and for my 31 inch tires, my 4.11 gear is too low. I bet with your 33 inch tires you would be happiest with 3.73 gears. Just my two cents! Good luck!
Post Fiend
Joined: Jan 2007
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From: Almost Heaven
A C6 is an automatic. But I agree, it would run better with the lower gears. I think he's more worried about being able to keep fuel in it though.
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From: Fayetteville Arkansas
Im not to worried about gas mileage for this will be my weekend toy, and i have both a small block C-6 and a NP435 it just seems my NP435 is geared so low i would not be able to wind it out. Could i start from second gear and solve that problem. What is the difference in the NP435's 6.69 first gear and the C-6's 2.46. I want a good offroad truck but i would also like to be able to hammer it and run through the gears, should i sell the C-6?
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From: The Vieux Ford, Kansas
Yeah that is how I have always driven 435s, actually I have seen them marked L 1 2 3 in some GM trucks 1st is only used when pulling something heavy, or any other reason you might want a very low gear.
-Johnboy
-Johnboy
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From: Fayetteville Arkansas
Will the NP435 limit or have anything to do with what rpm i can bring my motor to, i have spent alot of money on my motor and would like to get full advantage of it. I know the work involved in changing over to a C-6 and i am willing to do so if neccesary, but if i can keep my NP435 and still be able to wind out to 5,600 rpm i will do so, it just sounds like when i rev the truck now with the 302 my tranny wants to explode
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From: Fayetteville Arkansas
I realize it aint gonna shift till i make it, its just when the revs get high my NP435 sounds like all hell is breaking loose and didnt know if that had to with the gearing in the tranny or not. Its a truck tranny and made for working not hauling ***, but when its time to sh*#t and get i would like to be able too, not just creep along
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Senior User
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From: Fayetteville Arkansas
Thanks for the info, you have changed my mind on doing a C-6 swap i am going to keep my NP435 and get it rebuilt. Do you have any specs posted on your 351c build, i had one and sold it and wish i never did, i also sold a 1970 460 with ported dove heads- what a idiot i am. IM also thinking about 4.11 or 3.90 gears. Can i put different ratios up front and back or do they have to be the same