Hi all! I'm contemplating which transmission I should use for a 12V swap into my Ex towards the end of the summer. I've driven an NV4500 behind a 12V and like it, but there's a bit missing as far as the spacing of the gears (which has been documented extensively). So, then I started looking into 6 speed variations and basically there are several choices, all of which have been done and documented and really it boils down to what a person wants and how much money they want to spend. So, my choices are:

NV4500
NV5600
ZF S6-650
ZF S6-750
G56

I found a guy locally that has a ZF6 out of a 99 F-350 (this is the ZF S6-650 to my knowledge and is maybe a little weaker than the 750). He wants me to make an offer on it. He said "something broke in the back half of the case". So, I know I'm into it for a rebuild. Any pointers on what I should offer as far as a price? Or what I should look for? What I don't want is to get into something that has a broken housing or something that can't be replaced. Thanks in advance!

 

Many years ago Dodge manual trannies (including so called "High Output" manual trannies) had a problem , that was referred as " falling 5th gear " . As I recall there was no permanent fix for it . The least trouble will be with the ZF , although it has got an oil pump and a oil cooler and sooner or later they could cause an issue .

At only 90 K miles (half of it towing approx. 12K 5th wheel trailer around the country ) , my ZF- 650 and clutch still original and untouched .
Good luck with your choice.

 

Thanks for the info! The 5th gear issue has been resolved to my understanding. I'm concerned that the gaps in the 5 speeds will cause me to want a 6 speed for both towing and daily driving. I'm also a little concerned the torque of a 12V may max out the ZF6-650. The 750 is rated a little higher. I do sit in a bit of traffic each day and the extra gear may prove to be worth the extra expense. I don't know much about the V10's. Do you have an opinion on the performance or longevity with respect to torque? I have heard those V10's are pulling machines. Thanks again!

 

If I am not misinterpreting , you are a performance oriented type of person , and I am reliability oriented . So , what makes me happy may not necessarily satisfy your needs.
Having said that, years ago I had the task of selecting a "tow vehicle" for a 5th wheel to travel around the country. Since I do not know how the handle diesel repairs and the high cost of those repairs forced me to eliminate diesel immediately. Then , I had to choose between Dodge V-10 and Ford V-10 . Dodge V-10 was a more powerful towing machine but gas consumption was also higher . Since manual tranny was my choice of transmission ( those years Dodge had falling 5th gear problem with their manual trannies and that coupled with higher gas consumption of Dodge V-10 ) Ford V-10 and ZF won . No regrets so far .

My Ford V-10 tows my roughly 12K 5er (rated for approx. 14K 5er ) , but its performance is marginal (all diesels are passing me on the grades but that does mean anything to me since I have a different state of mind (no girls in bikinis waiting at the top of the hill with a championship cup ). During 14 years of ownership of this truck , it went to repair shop only 3 times , and all because of A/C problems. Everything is original except AC compressor . When I was travelling with my wife around the country reliability was very important and Ford V-10 & ZF met that goal .
Good luck with your choice.

 

I actually want both performance and reliability. That's why I'm concerned about the drivetrain and making sure it's up to the task. Having said that, I won't be heavily modifying the 12V when it goes into the Ex. A little more HP and a little more torque than the factory setup. The NV's are proven behind the 12V, and from what I'm reading it sounds like the ZF6 is proven as well. First question is will it handle the torque. I think the answer is yes. Second question of how long will it last? With the external cooling system on the ZF I think that'll get me a long way. I won't be towing as heavy as 15K, but I may get to 10K+ at some point and I'll want it to be able to pull all day long and not have issues. From what you've said, it sounds like the ZF is a good transmission and will certainly handle anything I'll be putting behind the Ex. So now it's down really to preference of gear ratios/gear splits and cost. I do have 3.73's, so mine'll behave a little differently than 4.30's or 4.10's. Thanks for the info, it's good to have more information on how these transmissions have worked for folks.