Ford manual trans swap

[Ford4x4man]

I have a 1985 f-150 4x4 with 302 EFI with a 4 speed manual and want to swap for a five speed just wondering if the five is the same length as the four and any other problems that I might encounter.





Thanks, Darrell

[75K30]

The term "a five speed" leaves many options, trying to guess which five speed gear box you are considering is tough to do. Not all are equal in length, but your decision to upgrade the gear box is not difficult. Are you looking to find a better overall ratio for the highway? Would a gear swap in the diffs accomplish the same thing, (or better) for less money, and effort?

[Ford4x4man]

I would either like a five speed manual for towing or possibly get a four speed with overdrive. I would like either one of these to drop down my rpms on the highway too.



Thanks, Darrell

[Ford4x4man]

I can't put different gears in the diff because we built the motor for the gears that are in it now.

[75K30]

An engine only has a given rpm range that it makes optimum torque, and horsepower. Torque being the most important in your case. Gears are installed to keep the engine within these parameters to maintain the most effecient method of motion.
By changing the ratios in the transmission, or changing differential gears, you are obtaining the same results. The engine does not know the difference, regardless of who built it, or what gears you intended to use at the time.
If the 1:1 high gear ratio is still too steep, and you are looking to lower the final drive ratio by installing an overdrive, (.70 to .76:1) you are essentually doing ( almost the same as ) raising the diff gears by on size. If the truck has enough torque to pull your load well in gears 1 through 3, then the rings, and pinions might still be a better choice.
At any rate, just about any standard box will go into your truck, most adapters will allow the use of your existing t-case, slight differences in length should be expected, and will require driveshaft modifications.
None of the above is very difficult to do.
If you have your heart set on a 5 speed, the best choice would be an
NV 4500. It will have a 1st gear ratio of 6.34:1, 2nd 3.44:1, 3rd 1.71:1, 4th 1.00:1, and 5th 0.73:1. This is a gret veriety of gear choices. The best truck to find these from are chevy units from a 93 or 94. These will have the above ratios. Try to avoid the dodge ubits, as these have had problems with 5th gear. And no, they are not the same, there are design diferences.
Advance adapters will have the adapter to use your Borg Warner transfer case with the ford output.
Be prepared to spend some bucks for this swap. These transmissions are out of production, but they are the strongest out there right now. Another option would be a 6 speed ZF trans out of a later model ford, or the equal in a 5 speed. These are dig dollars, and will be difficult to bolt to your existing engine.
A M5R2 will bolt up, and was used in Full size ford a little after your vehicle era, perhaps a complete unit with t-case could be found, and installed in your truck, but this will for sure require drive shaft modifications.
Lots of choices to consider, good luck with your project.......

[Ford4x4man]

I think that i will try to find a truck that has what I need that way I can have all the parts that I will need, what years did ford put the m5r2 transmissions in?

[BigFootIsAFord]

The most practical thing to do to save gas would be to change the ring and pinion.

I'm guessing you have the NP435 transmission? Sure, it's bad on gas, but it is tougher than ****.

If you insist on changing the tranny, the Mazda 5-speed is a common swap in these trucks. Lots of info out there about doing this.

I agree with everything 75K30 said, though.

[BILL SADLER]

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