I have a ZF6 in my PSD and this is correct.

ZF6:
Low / Granny
1st
2nd
3rd
4th = 1:1
5th = OD
R

I thought the ZF5 was similar to the NV4500:
Low / Granny
1st
2nd
3rd = 1:1
4th = OD
R

T19 is sort of like an SM465:
Low / Granny
1st
2nd
3rd = 1:1

Going with a ZF6 in lieu of the ZF5 gives you one more gear, thus shortens the shift gaps even more. Same thing applies going with a ZF5 in lieu of the T19. The T19 has huge gaps. I have 4.10s in my IDI w/ a T19 and tach around 2450RPMs @ 55mph. I would love to have an OD. It would drop the RPMs and render faster travel at lower RPMs. With 4.10s I'd wager a ZF5 would shorten the shift gaps enough and be more cost effective for a swap. That being said, a ZF6 behind an IDI would be awesome.

 

I guess if thats how you want to label it.... but regardless of the ratio "low" is 1st gear. 4th is 1:1 on a ZF5/T19/NV... 5th is 1:1 on the ZF6

Also, the bolt patterns between the two are identical. The issue is the superduty 7.3 doesnt have an adapter plate, there for the bellhousing depth is off by about an inch.

 

How is the issue of the adapter plate fixed? Or is it not really a worry? I asked those guys about it over at PSN and he didn't really mention it...

 

this was a pretty good google search result:
How to put a 6 speed ZF in a 2wd IDI - Diesel Forum - TheDieselStop.com

thats a pretty cool looking site.iv scored some stuff from there a few times now.

 

Hmmm ya I have been over there a lil bit. I never saw that one. I'll have to read it.

 

Not to split hairs, but i would by no means consider the first gear in a ZF5 to be a "granny", at least in comparison to an old 4 spd, im talking top speed of 7mph in first gear with the one i had in my 79 lol, usesless. As for the ZF i always start in 1st, due to being a more usable ratio, and my effective final ratio is i bit high for starting in 2nd. But like NMB2 said, doesnt matter if its 7:1 or or 3:1 The first forward gear is first gear.

 

That was a good thread. It answered most of my questions I had.

 

FWIW the guy that did the first zf6 swap had access to a modern machine shop, and was very knowlegable in automotive engineering.

THis is not a shadetree type procedure. The bell housings do not match, the input shafts are different, ect.

Seems like a lot of work for very small advances. The gears are basically the same between the ZF5-6

Personally, a C6/GV/3.55:1 seems ideal! (shifting gets old after a couple hundred k miles)

 

The first forward gear is labeled LOW on my ZF6. The second forward gear is labeled 1st. FACT.

 

Narrow ZF5 (most diesels)

1st = 4.14
2nd=2.37
3rd=1.42
4th=1.00
5th=0.77

Wide ZF5 (gas and F450's without split t-case for crawl gear option)

1st =5.72 "granny"
2nd= 2.94
3rd=1.61
4th=1.00
5th=0.76

ZF6

1st = 5.79 "granny"
2nd=3.31
3rd=2.10
4th=1.31
5th=1.00
6th=0.72


Note that the OD gear in all three are similar. When I said "double overdrive" in my previous post I was referring to the ZF5's 5th gear plus my Gear Vendor's overdrive gear which produces a final overdrive output of 0.60 which is substantially taller than any of the mentioned transmissions by themselves. But, as NMB2 said, lower rpm's does not equate to better fuel economy per se. I see no huge advantage to a ZF6 unless you have a 2wd without a split t-case for a crawl gear, yet want a close ratio gear spread. Personally I don't care for the close ratio (just how I use my truck), and would vastly prefer the wide ZF5 over a ZF6. Of course I ended up with a narrow ZF5 because it's what I could find and what I could afford. I'm not terribly disappointed, but I'd rather have had the wide one.

 

ZF5 and ZF6 - 5 and 6 meaning forward gears. Doesn't matter if you call it granny and 1st-5th. Still a 6 speed forward. ZF5 has 5 forward gears, T19 has four.

I would just get a ZF-5 for simplicity. No real need for granny 1st or slight more spread when you realize the work needed to support a zf-6. ZF-5 plus a under direct over aux trans would give a far greater spread (basically 15 speed) and still be straightforward. I'd love a brownie

I've never been able to take off in anything but first unless going downhill or babying the clutch bad.... T19. Tops out at governer at 25 in first.

 

I've used the granny gear in my ZF6 quite a bit since I bought the truck at the end of '08. Usually with a load, on rough or steep terrain, or in bumper to bumper. With the lack of power in a NA 6.9, when compared to my PSD, I can understand the desire for a tighter shift range. From 3rd to 4th, my IDI is a turd unless I get after it in 3rd. That ZF5 range for the diesels looks good! I'd go with the ZF5 for simplicity's sake and cost effectiveness.

 

For those of us old enough, We can remember when The lowest gear in a "granny low" "4 speed" was not syncro'ed. It was truely a 3 speed with granny low. The factory labeled the shifter L,1,2,3. The lowest gear was not intended for normal use, just to get vehicle rolling or manuevering a trailer. Especially in the days of low power engines in heavy duty trucks. Of course this is just splitting hairs as you say.

 

Input shafts being a different size is of no importance, this is easily solved with choosing the right clutch disc for either a ZF6 or NV5600.

As I stated above, the main issue is getting the spacing correct since the 2nd gen 7.3 did not use a bellhousing adapter on the back of it, so the ZF6 bellhousing is deeper. You guys are misunderstanding what he means by the patterns being different. He is referring to the pattern on the block itself. On the IDI the bottom 4 bolts just have the spacer, they thread into the block, the top 2 bolt to the block, and then the Bellhousing bolts to the spacer, those are what need adapter, and its NOT a big deal to do so.

This swap is not complicated at all, and it doesn't take a special machine shop to do it, it could be done with almost using just hand tools.....

I also got told I couldn't put a 13" clutch behind my IDI..... but what do I know.

 

double post.