Let's talk Overdrives vs Gears

[War Wagon]

So my my '94 IDIT w/ 5 speed and 4.10's is awful in my mostly road speed driving. Power is just fine but I hate being reved all the time and fuel economy is about nonexistent. I bought a dually axle and I'm going to do the swap from SRW to DRW as you can see I need. I have wanted to gear the new rear to 3.55's but of coarse I have to do the front to match. The DRW axle I'm getting already has 4.10's so it's a bolt in if I stayed geared the way I am, which just sucks without another gear at the top. I recently ran into a US Gear Dual Range or what I'm told is an old Doug Nash overdrive unit for sale and I got to thinking. I like the idea but it has it's complications as well. Almost since I got this pickup I've wanted to solve my gearing issues with a swap from ZF5-42/4.10 to a ZF6/3.55, but I want to hear some more opinions on the overdrive/splitter units out there. The regular common ones like the US gear and gear vendors as well as some that may be more uncommon or custom.

Which are the best the toughest?
Pros
Cons

A little US Gear info. After reading this I really like the sound of this unit.
http://www.dieselwarden.net/temp/usgear/US%20Gears%20overdrive%20manual.pdf

Some quick calculations: ZF5 OD .76 x 3.55 gears = 2.70 final drive ratio
.76 x 20% US gear od .80 x 4.10 = 2.49

This would actually give a little taller OD with the US gear 20% OD. 3.55 over 4.10 gives 13% increase

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[junk]

I've looked at doing the ZF-5 to ZF6 swap. To me the gear ratios aren't enough different to do the swap. Also the ZF6 swap is fairly expensive and I've read that the clutches people have put together don't have very nice pedal feel. Now I was comparing it against my US gear/t-19 combo at the time so my comparison ratios may have been slightly off compared to a ZF-5.

I myself am going for the ZF-5/ US gear/ 4.10 route. I've had 3.55's/T-19/US gear for years and pulled all over with that setup non-turbo. Now that I've got my big enclosed trailer they don't cut the bill. I slow down too much on all the hills. My engine isn't built like your engine though.

I was asking about 4.10 gears a while back and most guys who tow and have had both gear sets like the 4.10's better.

I would suggest to keep the 4.10's and add the US gear. Or even look at Maximum-overdrive he sells a gearvendors that could be installed in the rear driveshaft as a kind of standalone unit.

 

[The Warden]

IMHO the biggest problem with the U.S. Gear overdrive unit is that they're no longer in production and have zero OEM support, so you have to get creative with spare parts. They're also not the easiest things in the world to find used, although they are out there. There's been discussion of using a two-speed rear axle shift motor, although I don't know if anyone's actually done it...and, the other parts are either off-the-shelf or can be fabricated. But, it's still an issue to consider.

A couple of threads that are worth the time:

http://www.oilburners.net/forums/showthread.php?65234-US-Gear-Dual-Range-Doug-Nash-Info

http://www.oilburners.net/forums/showthread.php?74495-US-Gear-Surprise

The GearVendors unit can be purchased new (and is VERY expensive new, like north of $2000), but it's been said that you can't engine-brake with a GV without risking damage to it.

Honestly, I'm on the U.S. Gear side of the debate, although I wish they were still making them new...

Either way, an overdrive unit gives you the advantage of being able to run at a lower freeway RPM but still have the lower gears to get yourself started easier. IMHO it's the best of both worlds, if you can get your hands on one...although there is the added complexity and purchase price (however, that's offset a bit by the cost to regear both axles).

 

[Black dawg]

I have been way happy with my us gear. My truck is 4.1 geared, with a 4 spd. Most of the time I just leave it in high, and start out in first. Being able to split gears (even OD in reverse) has been really handy. I have a zf to put in, when I get time, I imagine that will really help with mpg.

 

[HS108]

for you, I would stick with the 4.10s and put in a OD, you are gonna want those 4.10s to get that thing up and rolling, then once your at highway speed turn on the OD and boom.. money

 

[War Wagon]

It does weigh on the verge of 12K lbs, but like I mentioned the engine power side of things is good. I want to set the cruise at 80 and do just that, cruise. I'm about wrapped out at 80 now. i like the US gear for its rugged heavy dutyness. I like the way it shifts too (from reading the owners man on it). Of coarse, the thing that scares me is the parts availability. My thoughts on the ZF6 swap were that the lower first gear and closer shifts would compensate for the 3.55 gears. I just looked at ZF's website and it's unclear if I have a 4.14 or a 5.72 1st gear ration in my S5-42.

http://www.zf.com/corporate/media/zf_media_import/document/int_print_catalogs_documents/usa_4/S542_Transmissions.pdf

If I can't brake with the gear vendors and can't pull in double overdrive then I don't think I want that.

 

[jaluhn83]

I'd run the DNE/US Gear, but you'll need a 4wd unit - is the one you're looking at off a 2wd or 4wd? The 4wd unit sat between the t-case & trans and has a different housing & output shaft - not like a GV where both 4 & 2wd sit behind the trans/t-case and are essentially the same box with different adapters. I'm working on mounting a 2wd unit behind a 1356 t-case, but haven't actually gotten the final adapter done yet. Not a difficult project, but need a lathe and machine shop experience to make the adapter.

The overdrive gives you the advantage of splitting gears so you have effectively a 9 speed trans. This is the biggest reason I'm going to one.

How much are they asking for the DNE? $500-800 seems to be able market price, though that's for 2wd, 4wd seems to be very uncommon and likely would go for more. If you don't wind up getting it would you mind sending me a link?

Tim mentioned that parts are harder to come by, but I think the only thing that would really be an issue is the actual gears themselves, and wear on these isn't something I'd worry too much about. Bearings and shift motor/switch are easy to find and the common failure items. DNE units use brass thrust washers that can wear and would need to be made but don't seem to be hard to fab - just a brass washer basically. Also see some wear on the shift collar & fork which I haven't found a source for yet, however I have a strong suspicion they're both from some other common trans, and hence likely available once we figure out what the original source was.

 

[riotwarrior]

Add the second od

Keep 4.10

Driven F550 with 6sp...spread is ok but seeing major pita to work w IDI keep zf...if like get 1st gen ps zf...has lower 1st

Other option is locate a nice 3sp brownie box. Under direct and over. Place between tcase and rear diff for more gearing options.

JM2CW

 

[LCAM-01XA]

not like a GV where both 4 & 2wd sit behind the trans/t-case and are essentially the same box with different adapters

Somewhat offtopic, but they do actually make a model for Ford motorhome chassis with a 4R100 transmission with driveline brakes. AFAIK the 4R100+brake combo is pretty much the same setup as what was used in the F-Superduty - a 4x4 trans with a brake hanging out the back instead of a t-case. So if there is a GV that bolts to the back of a 4x4 4R100 and to the back of that GV bolts a driveline brake, what's to stop a resourceful person from using said GV with a ZF5 or E4OD in front of it and a t-case behind it? Even have pics of the GV in question somewhere, heck if I can find them now but I know I have them, and yes the thing looks exactly like it would slide right in between a trans and a t-case.

 

[jaluhn83]

I just looked at ZF's website and it's unclear if I have a 4.14 or a 5.72 1st gear ration in my S5-42.
.

You probably have a 4.14, IIRC most diesels had that and it's the gasser trannies that have the 5.72. Should say clearly on the id plate on the driver's side of the trans though if you want to look.

 

[dunk]

If you have enough power ZF5 and 3.55:1 is great. My 460 truck has that combo and can easily tow at 70 MPH and 2000 RPM. Would be nice to shave another 400 RPM but not worth the significant cost for me. My IDI has a C6 and 3.55:1 and annoyingly screams down the highway. I have a ZF5 I need to go through and swap in, but it's not gonna have the power to pull anything in overdrive. When that time comes I expect to do studs and bigger turbo, whatever it takes to have enough torque to pull with the trans and rear I want.

Personally for the aftermarket OD units I like the US Gear design better than GV, but lack of parts availability would keep me from going that route. I really like the Ranger boxes that go between trans and bellhousing, but obviously not an option for a ZF5. They say it won't work with an NV4500 either. I wonder if it could be made to work with one of the South American iron case ZF5s with separate bell.

 

[Clb]

Add the second od

Keep 4.10

Driven F550 with 6sp...spread is ok but seeing major pita to work w IDI keep zf...if like get 1st gen ps zf...has lower 1st

Other option is locate a nice 3sp brownie box. Under direct and over. Place between tcase and rear diff for more gearing options.

JM2CW

+1 on this^^^
My chebby utility is at 10 k ,,,, this is what I would be doing.
I just missed an old 3sp in a 60 dodge wrecker with a split boom.

 

[LCAM-01XA]

IDI-spec ZF5 with 3.55s is worthless for hauling heavy, you need the 4.10s for that. If you regear the ZF to the gasser wide ratios (5.72 first), or you get a PSD S47 with the 5.08 first, that's reasonable with 3.55s and a heavy load. Actually I suppose the PSD trans with the 3.55s will be the happy medium, it's overal gear reduction in first is about the same as IDI ZF5 with 4.10s so you can still get the load moving, but now you have a taller overall top gear to keep your engine speed down.

In any case, there are always trade-offs. If you want a setup that has the right gear for pretty much any speed/load conditions, you simply need more gears. Enter a DNE, GV, Brownie, whatever.

 

[Bart F-350]

Personally for the aftermarket OD units I like the US Gear design better than GV, but lack of parts availability would keep me from going that route. I really like the Ranger boxes that go between trans and bellhousing, but obviously not an option for a ZF5. They say it won't work with an NV4500 either. I wonder if it could be made to work with one of the South American iron case ZF5s with separate bell.

Hello, can somebody point me to some more info about these "Ranger boxes"?
do they have a website? I couldn't find on Google the only thing came out was a electronic batterybox or something like that?

Thanks,

Bart

 

[hce]

ranger gear box