Trannie Swap

[chris79bronco]

Hey guys new here, found this forum when I posted a question on my local forum, my question is, I have aquired a 7.3 liter turbo deisel from 99, the setup includes everything but the tranny (took body off and left the wiring, i bought everything else). I searched for a auto tranny for it and found they were pricey, but i found a zf5 speed from a 97 turbo deisel. Will this tranny work with my 99 motor and will it affect the way the motor runs because the original was a automatic???

[elibenson]

you'll need a couple things. New flywheel, pressure plate, hydraulics, petal assembly, but most importantly, you will need a new PCM from a truck of the same year that was a manual. By the time you bought all that, and spent the time messing around with it, you could have spent the same amount on an automatic.

[chris79bronco]

well the tranny i found was 450 for all of that (tranny, hydraulics, pedal assembly) but i would buy the new clutch kit, but i went and looked at prices and the 97 clutch is different from the 99, which kit do i get?? both kist include a flywheel, will the 97 flywheel bolt to the 99 motor?? Once I get done doing all this conversion wont the standard setup be stronger than the 4r100?? Ive heard alot of bad things about those trannys

[elibenson]

4r100 is not a bad transmission. Now, let me tell you, I've broken a lot of them, so I know.. Wait, that doesn't sound like a vote of confidence. No, seriously though, they'll take a beating. I just tend to beat on them too much. Not all of them were broken by me, but my uncaring, heavy-footed medics. Every one of them that I replaced, I have never broken again. The mechanic that I have rebuild them does a heck of a job, and he's cheap (~$1500).

I don't know exactly what clutch/flywheel combination people here have been using. I know it is a popular switch for people to do (4R100 to ZF6). I am pretty sure that the flywheel from a 97 will bolt up exactly, since it is the same block and crank. I would guess that you ought to go all 97 parts. The only hurdle that I can see is the PCM swap. Oh yeah, you will need to have a drive shaft made, most likely.

[chris79bronco]

yea the riveshaft will already have to be lengthened cause the truck has 24" of lift and 49's, I was warned about the tranny holding up to the tires. The ZF6 is a 6 speed right?? I think this one is a 5 speed. But I found a 4R100 on ebay rebuilt for 900 bucks, dont know if i trust buying something like that off ebay but it was a good price i thought

[elibenson]

The ZF6 is a 6 speed. The high (od) gear and the low (L) gear are the same as the ZF5, but the middle gear ratios are spaced different with the addition of 1 gear. So no major difference really.

About the ebay 4R100, just look at the person's feedback and ratings. If it is close to 99% good, that is usually good enough for me. After all, you are not going to make every one happy all the time. Even if it is not your fault.

Most likely, it isn't truely "rebuilt" it is probably *repaired*. That is, what ever problem it had, some mechanic repaired the problem, not necessarily rebuilt the entire trannie. Now, you just got this truck, and you are trying to get it running on a reasonable budget. If you go for the ebay trannie and it lasts a year or two, by that time you might be in a position to put in a Built 4r100 that will handle WAAAY more than a ZF5. Stock ZF5 to stock 4r100, is a toss up to me. If you had a ZF6, then I would probably go with that. If you ever start to go with some serious horse power though, the auto is the way to go in my opinion. It just needs a few little things. Performance valve body, big cooler (the kind that came on the 6.0l), and some good tuning (Tony Wildman or DP).

Nowadays, the auto is the "standard" transmission, and you have to special order a manual. More than that, the auto trannies are the only trucks that come with 350 HP from the factory. The manual ones come with 325. Another thing is that the manual trucks have a lower Gross Vehicle Weight Rating than the autos. Ford, at least, thinks the new autos (5 speeds) are tougher than the ZF6. Now the 5 speed auto is a different animal, but it shows that an auto is capable of just as much, if not more than a manual.

[chris79bronco]

i think ill go auto, lol thanks for the help and the advice man

[elibenson]

No problem. I'm surprised that I am the only one that responded. Usually there are better people than me to give this sort of advice. You might give it a couple more hours before you make a final decision. Some body might still pipe in with something pertinent.

[Jarrod B]

if you do a lot of city driving, an auto is nice but can kill mpgs. i have the 97 e4od auto in my truck and im happy with it. dads has the zf5 in his and was rebuilt a year ago.
i wouldnt go with a 97 obs tranny for a 99. stick with the trannys that came with that year. zf brand is a good brand if you take care of them, but if you are hard on it like power shifting, it gets expensive to rebuild it