except after researching the trans tag I have a NP435 made in 84.
Transmission help
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Senior User
Joined: Aug 2008
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From: Fayetteville Arkansas
Transmission help
Hello everyone I just bought a 1981 F100 2wd SB Swiss cheezer frame truck with 84,000 miles and in good condition that I’m wanting to turn into a weekend cruiser/Hotrod. It has the wheezer 255 V8 that runs really nice but it’s getting yanked for an aluminum headed, roller block 393w that I have.
I ran the codes on the door and it says it has a 3.00 rear gear that will be changed and a transmission code B which should make it a T-170 except after researching the trans tag I have a NP435 made in 84, I know the NP435 is a heavy duty trans from my experience with 70s model trucks I’ve owned but it’s not gonna work with my plans so I’m wanting to swap but have no idea on swaps for this year truck and my research is not finding any good info.
So my question is what trans should I be looking at and what’s involved? I am willing to spend the money on a new trans but I’m not trying to go broke in the process, I’m trying to decide between a Tremec TKO, C4, C6, AOD or even a 4spd toploader if I can can find one. Any help or advice in the right direction would be appreciated thanks
I ran the codes on the door and it says it has a 3.00 rear gear that will be changed and a transmission code B which should make it a T-170 except after researching the trans tag I have a NP435 made in 84, I know the NP435 is a heavy duty trans from my experience with 70s model trucks I’ve owned but it’s not gonna work with my plans so I’m wanting to swap but have no idea on swaps for this year truck and my research is not finding any good info.
So my question is what trans should I be looking at and what’s involved? I am willing to spend the money on a new trans but I’m not trying to go broke in the process, I’m trying to decide between a Tremec TKO, C4, C6, AOD or even a 4spd toploader if I can can find one. Any help or advice in the right direction would be appreciated thanks
Fleet Mechanic
Joined: Jul 2003
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From: Atlantic Canada
I'm swapping an M5OD-R2 5spd out of a 1991 F250 2wd into my 1984 2wd Flareside. For my truck, I think it's a pretty straight forward swap since I had factory hydraulic clutch (which didn't show up until 1984).
I haven't installed it yet, but will be soon. For my application, it's a very easy swap, even my existing driveshaft fits/works.
Some guys dislike this transmission because it's not heavy duty enough. I like it because it was in the 1988-up trucks with the same engines/chassis, so it is a straight forward swap, and fits well.
Not sure what it would take to make the clutch work though in a 1981. Somebody on here would know if it has been done.
I haven't installed it yet, but will be soon. For my application, it's a very easy swap, even my existing driveshaft fits/works.
Some guys dislike this transmission because it's not heavy duty enough. I like it because it was in the 1988-up trucks with the same engines/chassis, so it is a straight forward swap, and fits well.
Not sure what it would take to make the clutch work though in a 1981. Somebody on here would know if it has been done.
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Senior User
Joined: Aug 2008
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From: Fayetteville Arkansas
I’m looking for something that will hold up to my 393w and I know that I have a manual clutch I’m just not sure of my options when it comes to transmissions, I’ve looked at the Mazda and ZF but at this point I’m leaning towards the Tremec TKO if it’s reasonably possible
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Joined: Apr 2004
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TKO won't let you down.
TREMEC 5-speed 6-speed Transmission Conversion solutions for classic and modern muscle
TREMEC 5-speed 6-speed Transmission Conversion solutions for classic and modern muscle
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Senior User
Joined: Aug 2008
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From: Fayetteville Arkansas
Thanks! How much modification will it take to put a Tremec TKO in this truck? I’m also open to a built C4 or C6, I like the idea of the Tremec I just don’t know what would be involved to make it happen
Ford Parts Specialist
Joined: Nov 2006
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From: Simi Valley, CA
TRANS code A = New Process 435 4 Speed: 1965/72 F350; 1965/89 F100/250.
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Senior User
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From: Fayetteville Arkansas
Yeah obviously it’s not the stock trans as a NP435 is now in it I don’t care what used to be in it I looked up the trans code B for a 81 F100 and came up with the T-170 maybe that was bad info but it has a NP435 and I’m looking to ditch it as I don’t need a granny creeper trans I’m not building a off-road or towing vehicle
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Senior User
Joined: Aug 2008
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From: Fayetteville Arkansas
Thanks Dave I realize a T-5 won’t last long behind my motor I’m just wanting to know about a good trans choice for my application, I really would like to know about what is involved in the different swaps and what I’m looking at so I can make a choice, I’m looking for advice from people who have made these swaps. What would you put behind a 450hp street truck?
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You would used your existing stick bell and clutch. Trans is available with the Ford pattern. You need to confirm input length.
Then shifter location, cross member and mount, and drive shaft.
IMO an automatic is easier on the rest of the drivetrain and could use more stock parts. (big maybe there)
If you decide to make long runs, pop a Gear Vendors on the back of it.
All of this costs money of course. But then you have a high dollar motor and it's clear from your posts that you are not interested in a $50 transmission, so get the checkbook out.....
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Joined: Jan 2001
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From: Virginia
c6 would be the easiest approach. It would be a bolt in since it was stock in these trucks, and it is a very strong tranny. You would have to find a 2wd version with a small block bell pattern. I understand they can be hard to find in a 2wd version and the small bell pattern.
The c4 would be a easy swap also, and it can be modified to take the power of your engine. It would be easier to find with the small block bell pattern.
All the original manual transmissions that were original and be a bolt in, are truck transmissions with long shifter throws. While they would be a easy bolt in swap, I get the impression that is not what you are looking for.
The c4 would be a easy swap also, and it can be modified to take the power of your engine. It would be easier to find with the small block bell pattern.
All the original manual transmissions that were original and be a bolt in, are truck transmissions with long shifter throws. While they would be a easy bolt in swap, I get the impression that is not what you are looking for.
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Senior User
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From: Fayetteville Arkansas
Yeah I’m not interested in a $50 junkyard transmission and I don’t mind getting the checkbook out, I’m looking for a trans swap that will work well in my truck and behind my motor and what is involved in the swap. I’m trying to decide on a manual or auto and what works in a 81 F100
FTE Legend
Joined: Nov 2015
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From: Angier, NC
A lot depends on what "you" want, auto or stick?
Also I would not get hung up on its a truck. Look at it as a different body Mustang. Trany cross members & drive shafts can be made up easily for either trany.
An auto would be the easier of the 2 to install as you don't have to deal with clutch linkage. That could be a little easier with hydraulic setup.
Shift linkage you could use a cable shifter mounted on a pedestal between the bucket seats.
Flex plate to work with your motor, balance right.
Converter with the right stall speed to work with motor & weight of truck.
If auto I think I would look into the C4 as the C6 is larger, heavier and takes a little more power to run, But if the C4 build up to take the power of the motor was close in price of the C6 I would have to rethink this.
Depending on shifter & valve body either trany you made were you have shift it.
For stick as said clutch linkage needs to be dealt with.
Bell housing, clutch disc/PP assy. to work with the input shaft of the trany you use.
Flywheel to work with your motor, balance right.
Where the shifter comes out to clear seat/dash in the truck. Some times you can find a shifter stick/handle to clear them.
They are just some of the things I can see needing looked at for this swap.
I also don't remember seeing a lot of swaps in to trucks like you seek and why you are not getting a lot of replies.
Sometimes we have to be leaders ...... be the first to do this swap and post when you do.
Dave ----
ps: that Ford WCT5 was installed in a 70 AMC Javelin using AMC car & Jeep parts and no I was a follower not a leader in that swap LOL
Also I would not get hung up on its a truck. Look at it as a different body Mustang. Trany cross members & drive shafts can be made up easily for either trany.
An auto would be the easier of the 2 to install as you don't have to deal with clutch linkage. That could be a little easier with hydraulic setup.
Shift linkage you could use a cable shifter mounted on a pedestal between the bucket seats.
Flex plate to work with your motor, balance right.
Converter with the right stall speed to work with motor & weight of truck.
If auto I think I would look into the C4 as the C6 is larger, heavier and takes a little more power to run, But if the C4 build up to take the power of the motor was close in price of the C6 I would have to rethink this.
Depending on shifter & valve body either trany you made were you have shift it.
For stick as said clutch linkage needs to be dealt with.
Bell housing, clutch disc/PP assy. to work with the input shaft of the trany you use.
Flywheel to work with your motor, balance right.
Where the shifter comes out to clear seat/dash in the truck. Some times you can find a shifter stick/handle to clear them.
They are just some of the things I can see needing looked at for this swap.
I also don't remember seeing a lot of swaps in to trucks like you seek and why you are not getting a lot of replies.
Sometimes we have to be leaders ...... be the first to do this swap and post when you do.
Dave ----
ps: that Ford WCT5 was installed in a 70 AMC Javelin using AMC car & Jeep parts and no I was a follower not a leader in that swap LOL