How hard would a 2.8 to 4.0 OHV swap be?

[Kevin Evans]

I'm getting kinda tired of the gutless 2.8 in my 84. I installed CFI and got that working alright, but I'm interested in swapping to a 4.0 OHV since they're available everywhere.

I have the TK4 transmission. Can I just reuse this transmission or would it get torn up by the 4.0 motor?

 

[adsm08]

The 4.0 will drop in place of the 2.8 perfectly, physically speaking. Wiring and such will be the biggest part of the project.

I would replace the TK with an M5OD, which is a much stronger transmission. That will be a bit more work on your truck than on an 85+, as the holes for positioning the trans cross member correctly probably aren't there like they would be on the later trucks.

 

[rusty ol ranger]

A TK would hold up for a while as long as you were nice to it. The TK is slotted inbetween the FM145/146 and M5OD for strength.

 

[fastpakr]

There's no basis for that statement, as far as I know. All of the early FM and TK transmissions had a significant history of failure. Also, the newest TK is nearly 30 years old. Even the FM can be no newer than what - 1992? The Mazda, while far from perfect, was designed for use behind the 4.0 and generally held up well in that environment. It was also continuously produced from the late 80's until the end of Ranger production.

 

[adsm08]

Generally the TK and FM transmissions are considered weak behind a 4.0 for one common reason. The input shaft uses a ball bearing, not a roller bearing. This puts all of the torque load of a takeoff on the tip of the ball damaging the bearing. The M5OD uses rollers, and so it spreads that load out over a larger surface that is less prone to fracturing.

Also, the FM transmission (at least the 145/132) had a habit of splitting the OD gear into pieces, and that was behind a 2.9!

 

[rusty ol ranger]

There's no basis for that statement, as far as I know. All of the early FM and TK transmissions had a significant history of failure. Also, the newest TK is nearly 30 years old. Even the FM can be no newer than what - 1992? The Mazda, while far from perfect, was designed for use behind the 4.0 and generally held up well in that environment. It was also continuously produced from the late 80's until the end of Ranger production.

The basis for that statement is back in the day on here most of the old trans gurus agreed the TK was stouter then an FM145/146.

But no where near as strong as the M5OD.

Ive never had a 145/146 so i cant really say how shitty they are, however, i know ive beat the TKs hard and never lost one.

I had an M5OD in a 93 F150 with a 300 at one point for a few months, but they seem to hold up till they start leaking.

All im saying is i wouldnt be afraid to run the TK and then when/if it explodes swap in an M5OD. If you get the motor/trans as a unit, then by all means have at it. A TK is worthless to just about anybody as a standalone part, so why just scrap it without it being destroyed first? It might outlast the truck, even with a 4.0. Who the hell knows?

Personally you could get a frickin A4LD to stand up to a 460 as long as it was mounted in a festiva and you never went past 1/4 throttle.

Thats why i said If you take it easy

EDIT...

Wasnt there an adaptor out there where you could run a "real" trans from a 300/302/351W behind a 2.8/2.9/4.0?

If there was id find a ZF from behind a 351 or a T18 from any of the above and never worry again