Hey guys, I was just wondering if there are ANY kind of transmissions out there that I can swap my NP435 transmission with. I have a 79 4X4 with a 351 Cleveland in it. My Transfer case is a Dana 21, I just want to know if there are ANY options out there for me without having to Change my drive shafts.......fingers crossed.

 

Why change trannies? If it isn't broken, leave it alone. The NP435 4 speed is a marveled trans. I have it in my 78 f250 4x4. Ask any 4x4 expert, they'll tell it's a rock solid transmission. It's damn near bullet-proof. I'd put an NP205 transfer case on it though. That's probably your best combo for durability off-road NP435+NP205. Just a little bit of info: the first gear ratio in a NP435 is 6.69:1 !!!!!!! I've never seen a lower first gear ratio, GREAT FOR PULLING!!

 

[: the first gear ratio in a NP435 is 6.69:1 !!!!!!! I've never seen a lower first gear ratio, ]
*****

First off I agree, the 435 is one hellua tuff trans. Running one myself.


Point of clarification,,not all 435's are 6.69 low gear. There are some 4.78's out there also.

The SM420 has a 7.05 low gear. Lowest I'm awear of.

DSD
69F350
390_4sp

 

Running an NP435 myself, I have to agree with these two fellas. You won't find a better transmission for a 4x4. They are very dependable and reliable. Not only does it have one of the lowest 1st gears out there but they are easy to rebuild and maintain. Personally...I wouldn't get rid of it.

 

thanks....didnt know about that other trans w/ 7.05:1

 

Dirtyside, what is the sm420, and what is it used in ? is it like a fuller or something?

I think he may want to ditch the NP435 for the lack of overdrive, only reason I could think of to get rid of one of the best tranny's ever made......I agree the NP435/205 combo is the best on and off road set up ever offered from the factory, Glad my truck is equipped with these gear boxes

 

i have a t-18 myself, which is right up there with the np-435, they are both great transmissions with the granny low 1rst and and iron case....etc, the sm 420 does have a lower granny, but it was used in chevies up till about 67? it is a good tranny, but it is very small and will not withstand alot of torque like the 435 and the t-18. They were mostly used behind the straight sixes and small 283's which did not even put out 250 ft lb of torque. another thing is finding parts to rebuild it is very hard, if you could put it behind a 302, or 351, they would probably rip it apart with hard use

 

Actually the SM420 is one of the other guys (GM) transmissions. Used thru about 1967.

If you really want to make a change for the better go for the T19, it has a 6.25 low gear and is fully syncronized, even low gear.

 

 

so far I'm not overly impressed with the NP435 I have one in my 68 behind a 360 and it's getting realy hard shifting and is having a vibration, so I'm switching to a toploader. THAT's a strong tranny

 

The T-18/19 is supposed to be better than the NP 435, slightly stronger and better lubricated. I had to rebuild my 435 recently, and it very simple, and the parts inside look very stong. I believe many of you guys with poor acting 435's probably need some bearings, excess wear causes jumping out of gear among other things. Mine used to jump out of gear, but now stays in gear at full throttle, and shifts much easier.

As to the original question, your Dana 21 is going to make things difficult. It has an oddball input shaft that has a special 435 made just for it with a short output shaft with a spud shaft on the end. A 205 tranny has a long output shaft with a splined end only. Only other tranny that would bolt up to it would be a Jeep 3 or 4 speed, and you would probably have to buy adaptors to make it fit a Ford engine (although the 3 speed Jeep tranny supposedly bolts to a Ford 302 engine bellhousing.) You can't just bolt up a 205, you would need a new output shaft for the tranny, the extension housing, change the crossmember, and new driveshafts (yokes are different sizes.)

A Dana 20 would give you low range, and I think will go in place of your current Dana 21. Then you could put on larger tires, which would lower your highway RPM's which is your overall goal. You could use low range in 4wd to compensate for the larger tires, and with a Dana 20, you can get a twin stick control, which would let you used 2wd low range to get a huge load rolling.

fordmando
70 F-100 400 C6
78 F-150 4x4 400 NP435
George Selby