73 Bronco Trans

Alech1979 · Oct 8, 2004

I'm new to rebuilding 4x4s; i just got a 73 bronco. It has a manual trans 3 on the tree. I'm looking to convert it to the floor and I'm looking at changing it from a 3 speed to a 4 or possibly 5. Is there anyway of converting the existing trans or do I have to rip it out and get one off another vehicle and is so what vehicles make a good donor.

STLKIKN · Oct 8, 2004

No other 4x4 has a direct bolt in swap to the EB...
Figure out what you are looking for in a new trans.
There are a multitude of option available to you.
Check out the Bronco vendor websites, look through the Advance Adaptors
on line catalog. You should then be able to make an informed decision about what you need, how much you will be spending, and what other modifactions will be necessary in order to complete the swap.

Broncoholics · Oct 8, 2004

You can change the 3 on the tree to the floor yourself but it can take some time adjusting the rods to shift properly. Changing this will be a big performance change for you. You can go thru the gears quickly with a 3 speed but top speed will be limited. I have a NP435 4 speed from a 79 Bronco. It shifts slowlike a big truck. Advanced adapters makes an adapter to the D20 t-case youhave. Or do like I did and get the NP435 and Np205 out of a 79 bronco and make a custom cross brace, re-route the exhaust and new drivelines.

if you have the cash, get a NV4500 5 speed. If you have more to spend get an Atlas II t-case and you will be unstopable! >

My 2 cent...

S_bolt19 · Oct 8, 2004

Dont bother with the shift kit. They dont work well and tend to lock up on you. I had one in my first EB and had nothing but problems with it. I had the 3 on the tree with my current EB but saved up for an NP435 and I love it. It has a lower granny gear than most other trans out there and is bullet proof. You also dont need to go out and buy an adapter to make it fit either. That is a waste of money because you can make it work just fine. What places like Advanced Adapters and other parts warehouses dont want to tell you is that in order to make the NP bolt directly up to your 302 & D20, you just need to swap some bushings around. END OF STORY. They prey on people's willingness to listen to their advice in order to make a buck. Here is how to make it work....I have been running this for almost 5 years and have never had a problem.

There are 4 transmission cross member bushings. 2 thick ones and 2 thin ones. I dont remember which is on top or which is on bottom, but reverse them. Put the thick ones where the thin ones originally were and vice versa. That is all that you need to do for height under the trans tunnel. You need to have an NP435 out of a 2WD 70-72 F150. It has a shorter output shaft and you wont need to change it. If you buy one for a 4WD you will have to change the output shaft on the trans because it is longer and then you WILL have to buy the adapter or a new out put shaft. The 2WD trans will slide directly into your D20 xfer case adapter that you already have. The difference in length is zero. So no need for that expensive adapter to get the correct engine/trans/adapter/x-fer length. Bolt everything up and you are ready to go. Nothing else, pretty simple.

Have fun ---- Go 'wheelin

Broncoholics · Oct 11, 2004

I knew it! The 2wd NP435 bolts right up to the D20 the whole time!!!
I wish I knew this before I went with the NP435/205.

TallGuy · Oct 11, 2004

Sounds like that is the way to go.... I just took the body off of the 69 and am ready to start going through things. I would really like the 4 speed, T18 or NP435 - so it sounds as if this is a good way to go. All I want to know is should I replace the Dana 20, or is it stout enough for 35" tires and moderate wheeling?

Toby the Dancing Bronco · Oct 12, 2004

The cool thing about a Dana 20 is that it is a iron box filled with iron gears. It is what BTO called "Not Fragile." They are simple to rebuild and don't have chains to stretch, or light weight cases to crack. The bad thing is they are heavy and require a good tranny jack to lift. Mine had about 300,000 miles on it before I went through it last month, and it works better than it has in the last 10 years. I know several guys with the Dana 20 and 35-37 inch tires, and sofar, the only breakage has been axles and u-joints. Have fun!

S_bolt19 · Oct 14, 2004

If you go with a T-18 you WILL have to get an adapter between the trans and the D20. The T-18 is about an inch longer than the NP435 is. As far as the D20 and strength goes, why do all those Ch*vy and J**p guys want our running gear? Cause it is stronger and better than what GM or Chrystler put in their vehicles. Even the front D44 on a Bronco is stronger than the D44 on a CJ is. Just the way they are put together. If you are wanting to upgrade the D20 in any way, I would suggest going with an Atlas II. They have a super low crawl ratio in 4 low or you could just replace the guts in the 20 with gears from BC Broncos.

www.bcbroncos.com

They have a set of xfer case gears for about the same price as an Atlas but they are even lower than one. Just another option