I like all the strong opinions this topic always stirs up. For the record, I'm definitely not set on it. Just thought I'd get some opinions in case I find one cheap. ...though it doesn't sound like that's very likely.

 

This makes the most sense, but by god you really need to want that low first gear to go through all of that.

 

Have you done it Jim? I've been hearing some differing theories on the work involved. I'm just wondering if there's any first hand experience here that we trust. I know there's a guy on PSN or some foreign place who said he put in quite a bit of work but there's a guy running around town that says it was pretty much bolt in.

Not that I dont trust him but I'd trust your word before his.

 

I have not done it myself, but have talked with many guys that have and have seen a truck or 2 myself. As far as I've heard, it is all bolt-in IF you get all the donor parts to begin with.

 

If it is a lower 1rst gear that is the goal, I think the best solution for that is to get a ZF5 from a 460 gas truck that has the wide ratio gears, and swap all the guts into a diesel case. It won't do anything for fuel mileage on the highway, but for towing heavy it gives you a much lower 1rst gear, 2nd and 3rd are lower, 4th is the same in all ZF5s, and OD in the diesels is 0.77 and the gas trans OD is 0.76.....not enough of a difference to be noticeable. Also you will get a much lower reverse gear too. I think it would be the perfect towing trans, and I am currently doing one for my truck.

 

If you want a lower 1st gear, get a ZF5-s47 from a 96/97 truckAnd it bolts RITE in place of a s42

Diesel zf5 S47
1st Gear: 5.08
2nd Gear: 2.60
3rd Gear: 1.53
4th Gear: 1.00
5th Gear: 0.77
Rev Gear: 4.66

diesel ZF5 S42
1st Gear: 4.14
2nd Gear: 2.37
3rd Gear: 1.42
4th Gear: 1.00
5th Gear: 0.77

Gasser(BOTH s42 and s47 have the same ratios)
1st Gear: 5.72
2nd Gear: 2.94
3rd Gear: 1.61
4th Gear: 1.00
5th Gear: 0.76
Rev Gear: 5.24
Rev Gear: 3.79

ZF6 s650
Low 5.79:1
First 3.30:1
Second 2.10:1
Third 1.31:1
Fourth 1.00:1
Overdrive 0.72:

 

Great information guys, I didn't realize the gassers had that much better gearing.

 

Better gearing, I claim crappier gearing. I hate the low 1st in my zf5 that's behind my 460 with 410 gears. It's way too low and 2nd is a hair high. I'd love to have the 330 gear the zf6 has. Unless I'm towing, I barely ever use 1st.
Although in my 95 cclb with 350s I used 1st. But I never really towed more than 9k with it.

 

I also don't like the gearing in my 351 gasser. It has a 3.55 rear but 1st is still way too low. Maybe useful if you're moving a house, but with the engine revved all out you barely know your moving. 2nd is ok for starting out unloaded but too far from 1st if you are loaded.

Ok back to diesels. Anyone ever considered getting a custom gear set made for 5th gear. It wouldn't be cheap but I bet you could swing it for a ~$500 or so. I haven't looked at the current gear geometries, but I bet there's room to squeeze a larger counter shaft gear and proportionally smaller output shaft gear.

 

Actually, could you get a hold of an extra 3rd gear set and flip the gears from counter to output shafts. The 1.61 gear from a gasser would be a .64 ratio flipped. That'd be pretty sweet. The 1.42 3rd set from the -42 diesel would be a 0.70 ratio. Not bad.

I bet the synchro hubs wouldn't work on the opposite gear of the pair though. Maybe some machine work could make it work. ...and be cheaper than a complete custom set.

 

^^^^^^ Now THAT's thinkin' outside the box!.....

 

Oh boys....
Now I wish I hadn't sold my junky s42. That would have been fun to check out to see if it would work.

What 5spd was behind the v10 f450 superduty. I'd be interested in seeing if that could do like you said also. With 456/488 gears that thing screams down the road.

(Sorry, all my diesels are autos, but this thread has gotten into ratios and it's hard to stay out of it)

 

I actually like the 1st gear in my 460 truck with 3.55 and 35s. I would have to slip the hell out of the clutch in 2nd to start off

 

I would agree. I always wanted it a more useable gear, and with a tall tire I bet it's pretty nice. I only had 265s on my truck.

 

35's being the important thing there! i'm on 33's with my diesel, but plan to bump up to 35's next time I need tires. I bet i'll like my gears even better then.

and my gas truck sits on 245/75r16 right now, I think - which is basically a 31" tire. I guess I just need to go bigger on that truck, too!

as for the custom gearing - Bill has a tranny or two apart right now - maybe he can look into the possibility of 'getting creative' with gears. :-)