I have the 5 speed thinking about putting an newer 6 speed in it just looking for some info an input.

 

As I understand it (and someone will correct me if I am wrong) there is not much difference in the ratio of the OD gear (5th on zf5 and 6th on zf6). The main differences are in the lower gears (and obviously the addition of the extra gear).

 

I don't know anything about those ZF 6-speeds, but most people say that the benefits to the ZF6 are not in proportion with the amount of work needed to make it fit in an OBS truck, versus a ZF 5-speed, of course.

 

IMO, the juice isn't worth the squeeze. It's not a bolt in and go swap, you have to move the crossmember, swap drivelines, and do some other stuff to make it work and there really isn't much to gain.

 

As stated, not worth it, for the amout of work involved. Both the input and out put shafts are larger on the ZF6, so if you have a 4X4 you need to use the Super Duty transfer case, and clutch. The 6 spd has a oil cooler provision so that has to be installed. The 6 spd is taller, so the floor pan has to be modified for clearance. And there are probably other things needed that I'm missing, so it is far from a simple bolt in swap.

 

Wow yeah that's a lot or stuff to do for not much gain. I thought they would just just swap an go. Guess I'm sticking with the 5 speed thanks for the input!

 

Plus its just another gear to go through. I was all for a 6 spd at first, then i found out all that ^^ lol

 

Actually it's not another gear to go through. The ZF-6 is really just a 5 speed with a granny gear. Unless you've got a 20k trailer behind you, there's no reason to ever use granny gear with a top speed of about 3 mph unless you're stuck in traffic and want to roll along at 1/2 mile per week that you get from idle speed.

 

For those wanting to know:

ZF 5 Speed Transmission Specs

ZF 6 Speed ZF S6-650 Specs

If anyone is familiar with dirt bikes, think of the ZF-6 as a wide ratio version of the ZF-5, like a WR compared to a YZ, RMX compared to an RM, etc.

 

Actually, if you look at the ratios on those two pages ^^^^, the range is about the same; the ZF6 is _not_ a wider range than the ZF5. But that also must be a reference to the wide-range ZF5. There were two ranges; I forget exactly, but one version of the ZF5 had a 4.something first gear.

In any event, whichever ZF5 you have, unless you're faced with a shot transmission, and have a prospect for a really cheap ZF6, it's not worth the effort as an "optional" exercise. Esp. given the fact that you also have to work in the fluid cooler, which virtually no other manual tranny has.

 

I personally would like a granny gear. I tow a heavy 40' 5th wheel. I have considered this option and am not afraid to modify driveshaft and floorpan.
To me that would be worth it.

Does anybody have another option to get a lower than 1st gear?

 

4x4, manual hubs, leave them unlocked, launch in 4LO in second.... (IIRC, 4LO is something like 2.5:1)

Edit - oh yeah, it's not possible to shift into 4LO while moving, but is it possible to shift from 4LO to 4HI while moving?

 

Have you thought about an underdrive unit like US Gear or Gearvendors sell? The concept is similar to a split rear end like the larger trucks use. It would give you a a gear lower than 1st, as well as all the others so you'd basically get a 10 speed but keep your final overdrive ratio.

 

FWIW, I've read about (i.e. not actually experienced) people swapping in the 6spd. Apparently, you can use the automatic crossmember upside down and drop the tail of the transmission slightly for floor clearance. I still don't think it's really worth the end result for the average person.

Yeah, if you already have a 4WD, you could use the gear vendors underdrive for about the same cost (those 6spd aren't cheap and you'd need a different flywheel and clutch). Then you have a 10spd, that's 4 more gears!

 

Those specs for the ZF5 are not correct. those are the GASSERS gear ratios

The ZF5 for the diesel was offered 2 ways. the ZF5-S42(from 87-95) and the ZF5s47(96-97)

S42 rated at 420ft/lb

1st Gear:
4.14
2nd Gear:
2.37
3rd Gear:
1.42
4th Gear:
1.00
5th Gear:
0.77
Rev Gear:
3.79

s47 rated at 470 ft/lbs
1st Gear:
5.08
2nd Gear:
2.60
3rd Gear:
1.53
4th Gear:
1.00
5th Gear:
0.77
Rev Gear:
4.66

ZF6s650 rated at 520 ft/lbs
1st Gear:
5.79
2nd Gear:
3.31
3rd Gear:
2.10
4th Gear:
1.31
5th Gear:
1.00
6th Gear:
0.72
Rev Gear:
5.23

I can not really see the justification for the swap from a ZF5 to a ZF6. ESPECIALLY at the COST of a ZF6. If you can find one fro 1200, you are doing good. a ZF5 can be had for 500 or less. And alo the part to fiz a ZF6 are EXPENSIVE. I know, I just rebuilt one to the tune of $2100

My ZF5 costed me $450