I have 99 ford F550 that I use to pull a gooseneck trailer and am happy with this truck other than the excess rpm in high gear at highway speed. It has a 6 speed manual transmission . Does anyone know of a 7 speed for it? It is a 7.3 powerstroke diesel.
you can put a gearvendor (sp) overdrive in it, i would think
One of the aftermarket OD's would help as mentioned above. What are your RPM's and rear diff. ratio? Might be that a ring and pinion change would be best. I had a F-750 service truck that had a 7-Speed in it. I doubt it would bolt up to a 7.3 PS. The top gear ratio would probably not be much different than what you have. I was not impressed with this trans. at all. I was wanting my old 4+2 back.
The truck really needs one more gear or another overdrive gear. The rear end is a 4.88 I think and it needs the lower gears but also needs one more so you can cruise at 55 -65 and be at 2000 rpm or lower.
International used the same block in their trucks, there should be an adapter plate readily available to bolt on commercial transmissions. You would probably have to run the International clutch assembly and figure out how to link it to the Ford pedal. I'd imagine some tunnel work would be necessary too.
X 2 for the gearvendor unit, it's the simplest solution and it's durable. U.S. also makes a bolt in overdrive unit for a large variety of vehicles as well.
I had the same problem in an F-450 with 4.88's. I swaped out the 4.88's for 4.30's. Problem solved. If it's a 4x2, it's a pretty cheap fix. 4x4 is about 2-3X the cost. You wouldn't be able to run a Spicer 7 speed with a 4x4 because that would require a divorced transfer case. Not sure if you have 4x2 or 4x4. As was mentioned earlier, the OD unit on the 7 speed wouldn't give you much more top speed than the O/D unit on your ZF-6, but it is a bigger, heavier duty transmission. I have on in my 4800 and it's not too bad. Solved some problems that the non-OD 6 speed that was in there couldn't solve.
The overdrive in the F-550 6sp is probably a little taller than the OD in the 7sp. The 7sp gives you closer gears to get a heavier truck up to speed with a load, but lower OD because heavier truck don't need to go as fast according to designers. The aftermarket overdrive will fix your problem best, as it leaves you with the hauling ability you have, plus a cruising range. You probably have 4.88 or even 5.38 rear gears. Changing out to 4.30 gears will slow down the rpm 13% or 25% respectively, but if you tow, you will struggle a bit when loaded. You can get 25 to 30% with the aftermarket OD and not loose anything in the process.
like they said above Gear vendor is the best idea in my mind . Would love to have one in my Dodge 3500 but old Pete 379 is getting all the extra money now as work is almost at a stand still , so extra play money .
I didn't notice any struggling at all with 4.30's. In fact, I thought it towed as good or maybe even better. Owning the truck for 6 years (3 with 4.88's and 3 with 4.30's) gave me a lot of experience to speak from. These trucks don't need 4.88's to get the job done.