Hi I recently bought a 1988 F150 2dr 4.9L V6 Straight 4x2 RWD as my project truck , I'm going to be replacing the steering and suspension due to being pretty worn out, The engine and transmission run and sound good however , it's only a 3 speed with a low gear, it don't have the RPM meter on the dashboard so I don't exactly know what the RPM are when running it at 65mph , but my guess from the sound I would say it's somewhere in between 3 to 4500 RPM and I don't like that I would like to be able to run it at 65mph and have her just purrs and run smoothly, I was wondering if swapping the tranny to a 5speed would help accomplish that, Yall have any suggestions or recommendations??? I also plan on tuning up the engine and replacing head gasket and few other minor components

 

Your first step is to get a tachometer. Engines always sound like they're running faster than they really are. I would bet that you're cruising rpm is no higher than 3

 

Worse case is maybe 3000 rpm, but it depends on your rear gearing. Not sure if they geared those higher then 3.55?

No matter, if you want OD, then a 5spd would get you there. I don't think it would be a hard change over. Need to find one with a mechanical speedometer as the later(92-up) were electronic and no gear on the tailshaft to run a cable.

What kind of clutch set up is in those? Were they hydraulic like the 5spds? Or still mechanical? You'd need to purchase the hydraulic set up and install it.

 

By 3 speed I was assuming C6 so.... To the best of my knowledge in '88 the manual transmission choices were either a 4 speed or 5 speed.

My C6 Bronco with 3.55 gears would turn around 3,000 rpm at 65mph.

 

I'm not sure what the rear gearing is...it has 4 gears but the first gear is more of a low gear , I can bearly go to like 9mph before having to shift, and when I looked up the VIN # 1FTEF15Y5JNB39361 it says it's a 3speed

 

Most of the 4spd NP435 trucks had 3.08 gears. These turn around 2425 at 65 mph with LT 235/75/15 tires, which is the stock size tire.

If you happen to have 3.55 rears, the you would be turning 2800 at 65 mph with the granny gear 4spd.


Changing to an M5OD transmission will give you the following:

2250 rpm at 65 mph with a 3.55 rear

1950 rpm at 65 mph with a 3.08 rear

Above based upon using stock size tires.

 

If you give me the axle code and your tire size, I can figure out what your rpm is at speed.

You can too, it's just math.

 

P235/75R15 Axle-18, Trans-F, Spring-CD

 

 

Trans code "F" is a T18 or T-19 4-speed according to the chart I'm looking at. First gear being synchronized or not is the main difference between the two.

 

I think the gearing is 3.31, what would be the best option of 5spd tranny to swap it to ??

 

According to your sticker, you have a direct drive (1:1) transmission with a 3.08 rear axle. See my earlier post to see what speeds you would run if changing to a M5OD transmission.

 

If you reread his post closely he mentions:
That would be a creeper 4 spd.


With 3.08 gears, the OD will be nice. The deep first gear in a 5spd will make it start out fine. I had 3.55's in my '89 and 1st gear was near useless unless you had a big load on a hill. I was going to install 3.08's but sold the truck instead.

 

4speed creeper sounds right , I hardly even use that first gear since it's so low, I'm usually taking off on second

, I found me a M50D R2 tranny , should I just be able to swap them without having to add a adapter or anything??

https://spprecision.com/products/m5od-r2-m5r2-transmission-sale.html

Also any suggestion or tips that yall recommend on tuning up the engine ??

 

My only concern on the swap is what kind of clutch linkage does your current truck have? Hydraulic? Mechanical? I don't know what those transmissions came with.

The 5 spd takes a hydraulic system. Easily installed with parts available.

You need to confirm if that 5spd has a mechanical speedometer in the tailhousing. If it is a later model version it won't have a spot for a cable like your truck still uses. After 1992, they went to electronic speedometer.