Transmission or differential problem
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New User
Joined: Sep 2020
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From: Harlingen, TX
Transmission or differential problem
Hey guys,
Im new to the forum, I just finished restoring my 65 mustang and decided I needed a new project. I got a 1983 ford f100 flareside with a 300 4.9l inline with a c6 transmission.
The revival of the truck went smooth as it just had clogged fuel lines, then I replaced all fluids and the radiator. I noticed it sputtered when going about 50-55 during the first few test drives. I tried starting it up today but it wouldn't go in drive, the truck goes in reverse but when I put it in drive it jerks the truck without moving it. I jacked up the back end to get the tires off the ground and put it in neutral but the tires wouldn't spin when pressing the gas but when the truck is off I could rotate the tires by hand. When in park it idles great, the problem is when it's in drive in either 1st or 2nd. When in drive the truck shakes back and forth and when I try to hit the gas it almost feels like I'm stuck in mud and am only moving forward in small bursts(just a few inches at a time) . I'm stumped and would appreciate any help, im thinking the transmission is destroyed. I took some videos but can't upload them on here
Im new to the forum, I just finished restoring my 65 mustang and decided I needed a new project. I got a 1983 ford f100 flareside with a 300 4.9l inline with a c6 transmission.
The revival of the truck went smooth as it just had clogged fuel lines, then I replaced all fluids and the radiator. I noticed it sputtered when going about 50-55 during the first few test drives. I tried starting it up today but it wouldn't go in drive, the truck goes in reverse but when I put it in drive it jerks the truck without moving it. I jacked up the back end to get the tires off the ground and put it in neutral but the tires wouldn't spin when pressing the gas but when the truck is off I could rotate the tires by hand. When in park it idles great, the problem is when it's in drive in either 1st or 2nd. When in drive the truck shakes back and forth and when I try to hit the gas it almost feels like I'm stuck in mud and am only moving forward in small bursts(just a few inches at a time) . I'm stumped and would appreciate any help, im thinking the transmission is destroyed. I took some videos but can't upload them on here
Logistics Pro
Joined: Jun 2017
Posts: 3,982
Likes: 515
From: Edmond, OK
Did you check the condition and level of the transmission fluid?
Check out this thread:
https://www.ford-trucks.com/forums/1...ard-gears.html
Check out this thread:
https://www.ford-trucks.com/forums/1...ard-gears.html
Moderator
Joined: Jan 2001
Posts: 56,999
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From: Virginia
If you are positive that is a c6 transmission, then it has been swapped in anyway. I have never seen a f100 with a c6 transmission. They usually came with c4 or c5 transmissions. If that truely is a 2wd c6 transmission with a small block bellhousing, they used to be desirable trannies that the drag racing crowd wanted.
Thread Starter
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New User
Joined: Sep 2020
Posts: 3
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From: Harlingen, TX
Thanks for the replies, it looks like it is a c6 transmission according to the picture. I checked the fluid when I drained it and it looked normal, I also replaced the filter and didn't see any debris , it just looked clean.
Cargo Master
Joined: Jan 2019
Posts: 3,369
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From: Caraway, AR
If you are positive that is a c6 transmission, then it has been swapped in anyway. I have never seen a f100 with a c6 transmission. They usually came with c4 or c5 transmissions. If that truely is a 2wd c6 transmission with a small block bellhousing, they used to be desirable trannies that the drag racing crowd wanted.
Have you messed with anything on the transmission like the kickdown rod or opened it up to put a new filter in? Are the vacuum lines hooked up? Should have a soft line coming down from the firewall right behind the engine to a hard line. And a short piece on the other end to the shift modulator.
Thread Starter
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New User
Joined: Sep 2020
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From: Harlingen, TX
Mine came from the factory with a C6,
Have you messed with anything on the transmission like the kickdown rod or opened it up to put a new filter in? Are the vacuum lines hooked up? Should have a soft line coming down from the firewall right behind the engine to a hard line. And a short piece on the other end to the shift modulator.
Have you messed with anything on the transmission like the kickdown rod or opened it up to put a new filter in? Are the vacuum lines hooked up? Should have a soft line coming down from the firewall right behind the engine to a hard line. And a short piece on the other end to the shift modulator.
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Cargo Master
Joined: Jan 2019
Posts: 3,369
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From: Caraway, AR
When I did mine, I had to drop the valve body, but I don't remember why. When I put it back together I got the inner linkage out of place. Wouldn't go into park or something like that. Had to take it back apart and fiddle with it, got it in right the second time. I hadn't put any fluid in it when I noticed the shifter was off.
Come to think of it, I had to remove all of that to replace the shift shaft seal. You may not have taken yours apart as much as I did.
Come to think of it, I had to remove all of that to replace the shift shaft seal. You may not have taken yours apart as much as I did.
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From: Angier, NC
Is this a 4x4?
Dave ----
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From: Virginia
Never seen a 4x4 f100 either. I will shut up and learn something about the f100 having a c6 if I see the door sticker.
Cargo Master
Joined: Jan 2019
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From: Caraway, AR
https://www.ford-trucks.com/g/picture/12647711
https://www.ford-trucks.com/g/picture/12781774
Moderator
Joined: Jan 2001
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From: Virginia
Ok. I learned something. I also checked www.car-part.com and autozone. Both list the c6 also. Thanks for the correction. I think I am right on the 4x4 thing so far.
Moderator
Joined: Jan 2001
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From: Virginia
Look at this as a possible opportunity to put something better in there. Something with overdrive.