The NP 435 4 speed manual transmission is the transmission of choice when replacing a stock 3 speed. With the low 6.69-1 1st gear (sometimes referred to as a granny gear) it lets even those with 3.50-1 rear end gears go rock crawling. The great thing about this set up is that you still use your stock length drive lines and there will be no cross member modification needed.
We have installed 435's in many rigs. There are more than one model of N.P. 435 and this relates to bolt pattern. If you use a unit from a 1977 or newer pickup that has a married transfer case, this unit will have what is referred to as an A pattern because the lower bolt pattern is wider than the top. If you purchased a adapter, you must purchase a 28 spline main shaft also.
You will need a 4 speed tunnel cover. You can make the cover if you prefer but I think that after you spend hours trying to get it to fit right you will learn that expense of buying one would have more than worth the time you wasted trying to make one.
The installation is pretty straight forward. It takes about 1 1/2 to 2 hours to get the old unit out. It will have to be returned for the core charge. Then depending on what you do as far as clean up etc, will determine how long it takes to get back in. We had about 3 hours into the actual install, this included new clutch, pressure plate, throwout bearing and flywheel. You will need a good jack and some blocking. While you are in there do not forget to replace that 30 year old pilot bushing. One item that we found to be in the way was the exhaust. With a dual system we had to sort of roll the bell housing through then install the clutch fork and throwout bearing after we had it past the exhaust tubes. It was kind of a pain but after the 3rd trans we sort of know the trick.
You will have to ether turn the "t" handle or get a new shift knob for the transfer case as the "t" handle gets in the way. When you have the unit apart just remove the lock out guts from the lever as you don't need it anyway.
When you are all done you will find a great difference. To figure out the final drive gear ratio use the following formula. 1st gear ratio x transfer case ratio x rear end ratio. To give you an idea of the change here are the numbers from my rig.
Before: 2.99 x 2.46 x 3.50 = 25.74
After: 6.69 x 2.46 x 3.50 = 57.60
We tried the Rubicon on the old transmission and wiped out the clutch just before Spider Lake. Not only did I have to do a clutch on the trail but I had to drive out with a buddy all the way to Placerville to get a clutch (50 miles). Now with the new low gearing of the N.P. 435 I can go rock climbing and still go 70mph on the freeway.
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