When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I am about to lose the ability to shift into reverse with the ZF5 in my 1991 F-Super Duty with the 7.3 IDI. I have access to two other ZF5 transmissions; one from 1989 F250 with a 5.8 and the other from a 1994 F250 with a 4.9. Assuming that the diesel transmission has the close ratios and the gas transmissions have the wide ratios, am I going to see much difference by putting one of the gas transmissions behind the diesel? It looks like I might be able to move a larger house in low gear. Am I correct in my thinking that the front case/bell housing is all that will need to be changed? Any tips on making that change? Thanks!
Am I correct in my thinking that the front case/bell housing is all that will need to be changed?
No. The bell housing is part of the rest of the transmission. It is cast as one piece. How are you about to lose reverse? Have you checked the shifter and forks for damage? Maybe that’s the problem
Case has to be split to inspect forks. More common for the 5/R slider dogs and R gear dogs chewed up. Mine was when I rebuilt it and R was difficult to get into before rebuild.
I always shift into 5 then drops right into R. Same shift rail. Just keep clutch down entire time.
I suppose it could be forks, but it has all the symptoms of a worn synchronizer. Can take a long time to get it into reverse, and has got worse over time. Don't really want to take the time to rebuild it right now. I understand that the bell housing and the majority of the case is one piece; is it a big job to swap that piece between the diesel and gas transmissions? One of the transmissions only has 130,000 miles on it; for no more than I use the truck, it will probably last me for the next 30 years.
I understand that the bell housing and the majority of the case is one piece; is it a big job to swap that piece between the diesel and gas transmissions?.
You would be completely disassembling both transmissions in order to put the internals from the donor transmission into your case.
I suppose it could be forks, but it has all the symptoms of a worn synchronizer. Can take a long time to get it into reverse, and has got worse over time. Don't really want to take the time to rebuild it right now. I understand that the bell housing and the majority of the case is one piece; is it a big job to swap that piece between the diesel and gas transmissions? One of the transmissions only has 130,000 miles on it; for no more than I use the truck, it will probably last me for the next 30 years.
Not really a big job, but you do have to check bearing preloads and such. Problem is the small-block transmissions have a different input shaft geometry from your diesel, they're smaller diameter and possibly longer as well
Are we just not gonna talk about the fact that the diesel has a larger pilot bearing size at 1/4" vs 1/8" for the small block transmissions?
Or is the plan to swap just gears but no shafts between transmissions? Might as well do a rebuild of the diesel thing then.
I don’t know anything about that. I was pointing out to the OP that he is going to have to completely disassemble his diesel transmission. It isn’t as simple as “swapping that piece.” I agree it would be easier to rebuild his at that point or only replace the bad shift rail/fork that is causing the problem with reverse.
Actually if he had a big block ZF5 it would be easiest to swap housings - take shifter off, stand trans on its tail, undo reverse idler gear shaft bolt (just the front one), undo the 378 bolts that hold the housing to the tail, lift housing off. Do this with both transmissions. Swap housing, check bearing preload thru the PTO ports, adjust as needed, reassemble. Don't forget to add oil thru top cover before shfit tower.
I lost reverse on my zf5 and just replaced reverse and the syncro and put it back together, a lot easier than trying to swap cases.
On mine reverse popped out under any kind of load, the teeth on the gear and syncro sleeve where badly ground down, if the teeth on the syncro sleeve get bad enough, the sleeve can actually get stuck and you loose 5th and reverse.
Remove snap ring and pull off bearing
Remove 5th gear and it’s bearings
Remove snap ring and pull off syncro hub
Remove reverse gear
Reverse gear bearings, nothing to do here.
Badly ground down teeth which caused it to jump out of reverse.
New reverse gear and blocker ring, note the nice sharp teeth on the gear.
Rezvani's Latest Post-Apocalytic Monster Is a Ford F-150 Raptor Underneath
Slideshow: Called the Fortress, the 850-horsepower pickup combines Raptor underpinnings with military-inspired features, survival equipment, and a starting price of $285,000.
