4 speed to C6 conversion
Lead Driver
Joined: Sep 2003
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From: Other side of the sunrise
I had to move the cross member to line up the rear trannie mount when converting from a c-6 to a 4 speed NP 435. I suppose you would need to move your cross member as well but in the opposite direction.
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New User
Joined: Jun 2004
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Idahocrewcab and oldfordsnstone,
Thanks for the info - the cross member and mounting of the tranny were one of my concerns. Sounds like I can move the one I have to the correct position and bolt it in place.
I know there is a certain amount of power and drive train efficiency loss with an automatic transmission. I accept that as part of the convenience of not having to shift constantly.
It doesn't sound like there are any major obstacles to this conversion. Thanks for the input.
Thanks for the info - the cross member and mounting of the tranny were one of my concerns. Sounds like I can move the one I have to the correct position and bolt it in place.
I know there is a certain amount of power and drive train efficiency loss with an automatic transmission. I accept that as part of the convenience of not having to shift constantly.
It doesn't sound like there are any major obstacles to this conversion. Thanks for the input.
More Turbo
Joined: Jul 2003
Posts: 629
Likes: 1
From: Grand Rapids, Michigan
Have you considered the rear end gear ratio difference, when going form a manual to an automatic? I made the swap from a 3 speed to a c-6 in my 79 300 six and didn't change the rear end. The MPG ended up at about 11.67. I had to add a rear tranny support for the c-6. it bolted in. All works fine except for ther MPG.
Senior User
Joined: Apr 2001
Posts: 418
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From: South Central PA
Now you have me wondering...would a truck that came from the factory with a manual transmission normally have lower or higher rear gearing than an automatic transmission?I'm still working on the same swap myself in my 79 F250 4x4. Just got the 300 fired up today...runs like a clock!! FTE user HillbillyK, gotta thank you for that engine!
Junior User
Joined: Apr 2004
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I have a 74 crew 4x4 stock motor was a 360 has been swapped out for a 390 tranny is a C6 with unmarried(divorced) transfer, and I gotta say I love driving it it wheels great and is nice to drive in town. My only complaint with it is the turning radius sucks it is like driving a duce-n-half all over again with out the shaved head and BDU. Good luck on your swap and keep wheeling.
More Turbo
Joined: Jul 2003
Posts: 629
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From: Grand Rapids, Michigan
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I'll post after I have made the change to let you know how it goes.
The conversation around the gearing is a concern for me, but I will be going to higher gears next. I currently have 4:56's and will go to either 4:10's or 3:73's - I need to save up some money first.
Cheapevil; I can relate to your steering complaint. I have to carefully plan my entrance and exit to every parking lot. After I change my gearing, I am going to convert to the 1977 1/2 to 1979 steering gear. There is an article on this web site in the tech section that outlines the conversion. Also, if you go to Ebay and look under auto parts: steering and suspension: and search for "ford conversion" there is a guy selling all the parts needed to make the conversion. It is a lot of money, but well worth it - I had a standard cab 77 1/2 F250 that steered and turned more like a modern truck than the set up we have.
The conversation around the gearing is a concern for me, but I will be going to higher gears next. I currently have 4:56's and will go to either 4:10's or 3:73's - I need to save up some money first.
Cheapevil; I can relate to your steering complaint. I have to carefully plan my entrance and exit to every parking lot. After I change my gearing, I am going to convert to the 1977 1/2 to 1979 steering gear. There is an article on this web site in the tech section that outlines the conversion. Also, if you go to Ebay and look under auto parts: steering and suspension: and search for "ford conversion" there is a guy selling all the parts needed to make the conversion. It is a lot of money, but well worth it - I had a standard cab 77 1/2 F250 that steered and turned more like a modern truck than the set up we have.
Posting Legend
Joined: Sep 2001
Posts: 30,255
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Originally Posted by Sgt Wonderful
Torq: what does that mean, off set the difference, what difference?
I will be running a high torque 400 in my truck with a custom wide ratio C6, towing converter, an overdrive, a 3.07 ratio Dana 61, and 265/75R16 tires.
Senior User
Joined: Apr 2001
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From: South Central PA
Don't mind me, this is starting to get over my head a little...so if I leave my truck geared as it was with the 4 speed it will pull better? With the 4 speed 1'st gear was usually a little slow to pull out, and starting out in second I had to ride the clutch a little to get her going...all while pulling onto a busy highway at a blind hill with a half ton or more hay bale teetering on the on the bed! I'm not worried about speed or economy so much, the truck usually never gets more than 10 miles from the house, and usually never gets over 45 MPH.
Senior User
Joined: Oct 2003
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From: Gig Harbor, WA
Just completed '76, 4X4, F250, 360, NP435 to C6 &
I can tell you exactly everything you need to know. Mine works great but it wasn't a dance in the park. I knew I'd need rotator-cuff surgery if I left the 4-speed in.
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rheacox,
I am a new member to this web and am not able to send an e-mail directly to you. I would greatly appreciate your input,advice and answers.
I will be ordering my transmission this week from a local shop but probably won't start the conversion for a couple weeks. My truck already has a steering column for an auto without the indicators and lever - so it might have had a auto at some point in its past. At any rate, please feel free to contact me through this forum - or I will go out and post some more comments to surpass the required 15 and send an e-mail direct to you.
Thanks for the offer
I am a new member to this web and am not able to send an e-mail directly to you. I would greatly appreciate your input,advice and answers.
I will be ordering my transmission this week from a local shop but probably won't start the conversion for a couple weeks. My truck already has a steering column for an auto without the indicators and lever - so it might have had a auto at some point in its past. At any rate, please feel free to contact me through this forum - or I will go out and post some more comments to surpass the required 15 and send an e-mail direct to you.
Thanks for the offer