zf5-zf6 swap

[JonZ71]

how hard would this swap be? Really need a 6th gear lol.

[1Dieselman]

Well, first off overdrive gear in both is about the same ratio just the ZF6 has a much lower first gear. I have driven several ZF6 speed trucks and unless you are towing heavy in the hills first gear is rarely used. If you still want to swap you need a different clutch disc, your transfer case will not fit so then when you use the superduty transfer case your driveshafts won't fit, will need the trans cooler and lines and I believe a different clutch slave cylinder.

[JonZ71]

Soo.. realistically. Not worth it...? Just so high of rpms at 70 and at 3lbs of boost.

[1Dieselman]

Realistically, no because overdrive ratio will not change. What gear ratio and size tire are you running? What rpm's are you turning at 70?

[wishIhada5.0]

subbed for info...70 with 4.10's is not fun IMO

[ol_Blue97]

the zf6 has a slightly lower OD and not as far of a gap between the 3-4 shift.. let me see if i can find numbers

EDIT.....let me try to find numbers from ZF and not off a forum, but here they are

The ratios for the ZF6 are as follows:
Low gear 5.79
1st gear 3.30
2nd gear 2.10
3rd gear 1.31
4th gear 1.00
overdrive 0.72

The S5-42 IDI trans
1st Gear: 4.14
2nd Gear: 2.37
3rd Gear: 1.42
4th Gear: 1.00
5th Gear: 0.77

The S5-47 95-97 trans is
1st Gear: 5.08
2nd Gear: 2.60
3rd Gear: 1.53
4th Gear: 1.00
5th Gear: 0.77

And the wide ratio version of both is:
1st Gear: 5.72
2nd Gear: 2.94
3rd Gear: 1.61
4th Gear: 1.00
5th Gear: 0.76


edit... conflicting info
1st = 5.79, 2nd = 3.31, 3rd = 2.10, 4th = 1.31, 5th = 1.00, 6th = 0.76 Reverse = 5.23

[terryknight]

i have both and i agree low is pretty much useless. and you will need a different trans cross member.

i also have 4.10s and have no issues, then again i almost never hit 70

[judgesblind]

Not to steal the thread but how about changing the diffs to 3.73? I drove a 5 speed the other day with 4.10 and at 70 i was at 2500 rpm. My 2x4 with 3.55 sits at 2300rpm at 85. I was thinking about doing a gear swap had I bought the truck. And what would you be looking at rpm wise with 3.73s? at 70?

[ol_Blue97]

I wonder how a zf6 would be with 3.55s and 35s or similar... that low to first shift is difficult on the 6 speed tho..

[terryknight]

Originally Posted by judgesblind

Not to steal the thread but how about changing the diffs to 3.73? I drove a 5 speed the other day with 4.10 and at 70 i was at 2500 rpm. My 2x4 with 3.55 sits at 2300rpm at 85. I was thinking about doing a gear swap had I bought the truck. And what would you be looking at rpm wise with 3.73s? at 70?

there is a formula out there to give you this, i used to know it but have forgotten it.

and frank that shift is not easy

and pulling hills with 3.73 weight in at 20K+ lbs is not fun either the phrase no balls comes to mind. i really wish that dump truck had 4.10s