Purchased this truck today. There are a few minor dings and dents but it is 100% rust-free. It's a 1991 F-250.

Currently has a 460 in it but I plan on swapping it out to a 4.9L EFI straight six and a ZF manual transmission. I was preferring an eighth-generation 4.9L anyway because they have the highest HP rating.

I don't even have it in my possession yet but downpayment made and deal secured.

Would appreciate any advice, pitfalls, etc. that come to mind--thanks!

(it is currently an automatic transmission)

 

What's your reasoning for swapping a straight 6 in?

 

what gears does it have? This is important because depending what size tires you are going to run and what you plan on using it for (dd,towing, wheeling, all the above.) Power band is around 2500 rpm's.

 

Nice find congrats....

I also have to ask why go from the 460 to the 300 in a F250? Unless you have a fresh motor, trans, computer and wiring just setting around, you can drive an awful lot with that 7.5l before you can't justify the added fuel cost over the swap...Not to mention you'll enjoy the drive alot more..

I would keep it like it is...unless the motor is toast then I would rebuild it and still keep it..BTW, I've had both motors and there isn't a chance in hell I'd trade a big block for the 300 in a 3/4ton....

 

I have them both right now, (see sig), and my 3/4 ton would not be happy if it only had the straight 6. I love the motor in my little daily driver 1/2 ton though

 

I drive about 30,000 miles per year. My top goals are dependability, longevity and fuel economy.

I do not know what gears it has in it.

 

Question: the ZF transmission I'm looking for, does it need to be off a 4.9L engine and also 4x4 to have all the parts I'll need? If not what combinations are permissible? Also is there a VIN code that indicates the ZF transmission?

Thanks.

 

the zf will mount to any small block motor

 

Check the sticker in the drivers side door jamb.....Post the axle code back here....H9 will be a 3.55 Limited Slip....

 

As long as it came from a 4.9,5.0, or 5.8.. The 7.5 gasser or diesel wont fit. The bell housing is NOT removable..

 

I will do that but I'm not sure how confident I can be that it's original. The truck has been lifted...

 

Eh...If it were done by bubba in his backyard....And he was in a hurry to pick his sister up for prom....

I'd wager he didn't pay the $$$ to swap 2 sets of rings/gears.....

Worth a shot.....

OR....

You can jack the rear end up and spin the wheel, and watch the driveline....count the times the wheel turns/driveline turns....theres a formula hiding around here that'll tell ya for sure...

 

Side question: I thought I read somewhere that 1991's had auto-locking hubs, but I see what looks like manual locking hubs there?

 

They were notorious for going bad....So most people simply replace them with manual lockers....

 

Found a local junkyard has BOTH the engine and transmission I'm looking for! (don't know their price yet...waiting on another e-mail).