I have a 2001 F250 XL 5.4l 4x4 extended cab long bed with a 5-speed manual transmission. The synchros grind in some gears during shifts - especially 3rd gear. The truck has 165k miles on it, and the issue has gotten worse over the last few years. I get around this problem by double-clutching all my shifts (both up and down) - as my wife likes to say I have a high tolerance for inconvenience... But it's getting to the point where it's almost impossible for other people to drive my truck. You have to shift really slow; so slow you lose momentum while shifting. I checked the clutch pedal and the bushing looks fine. I don't think the clutch is dragging. I can shift into 4th gear fine, but 3rd requires a double-clutch to not grind. I tried changing the fluid which didn't make much of a difference. So it seems like the problem is the synchros, which means a rebuild.

Anyway, if I have to pull the transmission for a rebuild that got me thinking about swapping in a 6spd. It would be really nice to get rid of that huge gap between 3rd and 4th that always makes me curse when towing up hills. I know the 1999+ diesels and 2002+ gassers got the 6spd transmission. What would I need if I wanted to swap in a 6spd? Do the transfer cases bolt up? Are the driveshafts different lengths? Any thoughts if it would be worth the hassle?

 

Diesel vs. Gas is Close Ratio vs. Wide Ratio.

Input shafts are different length, clutch diameters are different, clutch depth is different, bell housing patter is different, crank to flywheel bolt pattern is different, weight on flywheel for motor balancing might be a consideration on the flywheel, starter to flywheel, flex plate. Transmission Cooler and lines for the ZF6. Hump for ZF6 is pretty tall.

 

Thanks for the speedy and detailed response! That is quite a list of differences. Sounds like it's not worth considering. I guess the lesson is I should have held out for a 2002+ truck!

 

I think I've seen some threads here about similar swaps. I had done a little research back when I had an '01 v10/zf5. Not extensive but just for fun. I do think it is possible, you'd need a GAS 6-speed, also it's transfer cases, probably would have some driveshaft mods required. It is possible, if you can keep double clutching for a while, you'd have time to plan it.


I think Copperfarm was replying to swapping in a diesel transmission, i may he wrong, but I think thats what he was referring to

 

ZF6 was manufactured for Diesel or Gas motors with completely different gear ratios to match the torque and RPM range of the motors. A mountain of research, you'll find a few postings where people have done the swap but they are missing the details.

 

I had a ZF5 in my 95 F250, I was getting grinding in 3rd and reverse, same thing, I had to shift slow and DBL Clutch, I took a real hard look at the rubber cup inside the reservoir, it was cut near the lip at top causing fluid to go inside the cup, I found a new cup and changed it....clutch & Trans worked almost like new again. Might just want to check.