1981 f150 4x4 t18 trans to dana 20 question

[rjrobin2002]

I found a 81 f150 4x4 T18 at the junkyard with I assume is a np208 transfer case. Would a bronco dana 20 bolt straight up or I would just need that zf adapter ring?

 

[Jdgephar]

It needs an adapter between the transmission and the Dana 20. I don't know if the 4x4 T18 version works with this, or only the 2 wheel drive transmissions.

https://classicbroncos.com/tech/t18-borg-warner-4-speed-manual-transmission-guide

https://www.wildhorses4x4.com/early-bronco-np435-t18-4-speed-dana-20-adapter

 

[rjrobin2002]

It needs an adapter between the transmission and the Dana 20. I don't know if the 4x4 T18 version works with this, or only the 2 wheel drive transmissions.

https://classicbroncos.com/tech/t18-borg-warner-4-speed-manual-transmission-guide

https://www.wildhorses4x4.com/early-bronco-np435-t18-4-speed-dana-20-adapter

Thats what I was wondering, if I have a 4x4 already do I need that kit.

 

[Jdgephar]

I believe the issue with the 4x4 version of the transmission is the output length and spine count of the shaft that comes out of the back of the transmission. However, I didn't see anywhere in the links where it is specifically mentioned the difference between the 2x4 and 4x4 version of the ford T-18. Let me ask AI quick....

• Output Shaft Length and Splines: The 4x4 T18 uses a short output shaft designed for a transfer case adapter, typically featuring 31 splines on Ford models. The 2x4 T18 has a longer main/output shaft (often 29-spline) that cannot be easily cut down or reused in a 4WD setup. [1]

• Tail Housing (Tailcone): The 4x4 model ends in a short adapter flange meant to bolt up to a transfer case (such as a Dana 20, Dana 21, or New Process NP205). The 2x4 model uses a longer extension housing that holds a rear seal and a slip yoke for a two-wheel drive driveshaft

To me, this means you need the 2x4 version to have the correct spline count and length to reach the Dana 20 in a Bronco. The adapter gives the cross member in the Bronco something to mount to.

I'm sure you could use the 4x4 version, but that moves where the Dana 20 sits, which means moving/adapting the shifter in the cab, fabricating a different cross-member to hold it all, and new front and rear drive shafts of the correct length.

 

[jamesroney]

I believe the issue with the 4x4 version of the transmission is the output length and spine count of the shaft that comes out of the back of the transmission. However, I didn't see anywhere in the links where it is specifically mentioned the difference between the 2x4 and 4x4 version of the ford T-18. Let me ask AI quick....

• Output Shaft Length and Splines: The 4x4 T18 uses a short output shaft designed for a transfer case adapter, typically featuring 31 splines on Ford models. The 2x4 T18 has a longer main/output shaft (often 29-spline) that cannot be easily cut down or reused in a 4WD setup. [1]
• Tail Housing (Tailcone): The 4x4 model ends in a short adapter flange meant to bolt up to a transfer case (such as a Dana 20, Dana 21, or New Process NP205). The 2x4 model uses a longer extension housing that holds a rear seal and a slip yoke for a two-wheel drive driveshaft

To me, this means you need the 2x4 version to have the correct spline count and length to reach the Dana 20 in a Bronco. The adapter gives the cross member in the Bronco something to mount to.

I'm sure you could use the 4x4 version, but that moves where the Dana 20 sits, which means moving/adapting the shifter in the cab, fabricating a different cross-member to hold it all, and new front and rear drive shafts of the correct length.

Kinda.

There are two kinds of 4x4 in the pickup world. F100's, and F250's. The divorced transfer case 4x4 uses a "2x4 transmission." The married 4x4 uses a 31 spline output shaft, and an 8-1/8 inch long adapter. The T18 case is 1 inch longer than the NP435 case, so it uses a ~1 inch shorter adapter.

The 2WD pickup uses a bolt on driveshaft yoke with 28 splines, which just happens to slide into the Bronco Dana 20 input collar.

The aftermarket and anyone that speaks "ford" calls the divorced t-case 4x4 transmission a 2x4 transmission. If you saw one on the ground, you wouldn't be able to tell, except the 4x4 speedo output is plugged. As soon as you get into the medium duty stuff with a built it parking brake, all bets are off.

So yes, you absolutely want the 2wd version of the pickup transmission. Just keep in mind that it can be found in a 4WD F250 pickup. The vast majority of people see the output yoke bolted to the transmission and think: "2WD" The don't look deeper to see if it is a NP435 with a cast in but un-machined speedometer, or a T18 with cast in threaded pivot boss for shift linkage to the divorced t-case.

Because the instant you bolt it into an EB, all that stuff gets replaced.

As a general rule, if the transmission has a married transfer case, you don't want it. (unless you are going to run a 205...)

 

[rjrobin2002]

Kinda.

There are two kinds of 4x4 in the pickup world. F100's, and F250's. The divorced transfer case 4x4 uses a "2x4 transmission." The married 4x4 uses a 31 spline output shaft, and an 8-1/8 inch long adapter. The T18 case is 1 inch longer than the NP435 case, so it uses a ~1 inch shorter adapter.

The 2WD pickup uses a bolt on driveshaft yoke with 28 splines, which just happens to slide into the Bronco Dana 20 input collar.

The aftermarket and anyone that speaks "ford" calls the divorced t-case 4x4 transmission a 2x4 transmission. If you saw one on the ground, you wouldn't be able to tell, except the 4x4 speedo output is plugged. As soon as you get into the medium duty stuff with a built it parking brake, all bets are off.

So yes, you absolutely want the 2wd version of the pickup transmission. Just keep in mind that it can be found in a 4WD F250 pickup. The vast majority of people see the output yoke bolted to the transmission and think: "2WD" The don't look deeper to see if it is a NP435 with a cast in but un-machined speedometer, or a T18 with cast in threaded pivot boss for shift linkage to the divorced t-case.

Because the instant you bolt it into an EB, all that stuff gets replaced.

As a general rule, if the transmission has a married transfer case, you don't want it. (unless you are going to run a 205...)

Great info, I guess if get it I could use it in a f100 4x4 swap like this with its current np208, I've always wanted to do one.

 

[Broncobowsher]

The go to choice for decades was the NP435 from a 2WD with a 28 spline output. That was because it would fit (with aftermarket adapter) in place of the 3-speed and keep the original driveshafts.

As for bolting the Bronco dana 20 to anything except the factory 3-speed or factory C4 isn't going to happen without adapters.
Your thinking is correct in the ZF adapter. Reason being is the full size trucks ran the same transfer case input for decades. The large 6-bolt pattern and 31 spline input. The ZF adapter is the middle man that makes the Bronco small 6-bolt 28-spline Dana 20 mate up to full size truck large 6-bolt 31 spline output. While not commonly one to make the T18 to a D20, that adapter should work (for the factory married T18 4WD applications). Be ready for driveshaft length changes in any of these options.

 

[jamesroney]

Kinda.

There are two kinds of 4x4 in the pickup world. F100's, and F250's. The divorced transfer case 4x4 uses a "2x4 transmission." The married 4x4 uses a 31 spline output shaft, and an 8-1/8 inch long adapter. The T18 case is 1 inch longer than the NP435 case, so it uses a ~1 inch shorter adapter.

The 2WD pickup uses a bolt on driveshaft yoke with 28 splines, which just happens to slide into the Bronco Dana 20 input collar.

The aftermarket and anyone that speaks "ford" calls the divorced t-case 4x4 transmission a 2x4 transmission. If you saw one on the ground, you wouldn't be able to tell, except the 4x4 speedo output is plugged. As soon as you get into the medium duty stuff with a built it parking brake, all bets are off.

So yes, you absolutely want the 2wd version of the pickup transmission. Just keep in mind that it can be found in a 4WD F250 pickup. The vast majority of people see the output yoke bolted to the transmission and think: "2WD" The don't look deeper to see if it is a NP435 with a cast in but un-machined speedometer, or a T18 with cast in threaded pivot boss for shift linkage to the divorced t-case.

Because the instant you bolt it into an EB, all that stuff gets replaced.

As a general rule, if the transmission has a married transfer case, you don't want it. (unless you are going to run a 205...)

I'm going to reply to my own post, which I know is bad form...but people might find it useful.

There is a LOT of chatter in the transfer case adapter world that the Ford NP435 2WD and 4WD transmissions are interchangeable, and either or both can be great candidates for a swap. You will even hear that the Dana 20 adapter works on both NP435 2WD, and 4WD, and the world is made of rainbows and butterflies.

BUT that info is ONLY applicable to the Jeep/IH Dana 20 and Dana 300 installations. Jeep Dana 18's and Dana 20's adapter kits provide a new mainshaft for the NP435, and so the donor transmission can in fact come out of any Ford. And the transmission side is drilled for the square (2wd) pattern and trapezoid (married 4x4) pattern. So be mindful when you hear about adapters, that some people are talking Jeep, and others are talking Bronco. And they are different.

Google AI gets this wrong every time.