Engine/Transmission (1998.5 - 2002) NV4500 using different gear ratios

[NoSeeUm]

I have doing some scouting on the NV4500 and the NV5600, plus looking into some stuff like the Gear Vendors or the US Gear Aux Transmissions. Basically I really like the 5 speed for everyday driving. The exception is the leap between 3rd and 4th gears is a bit much pulling a load up a hill. I guess thats why there is the 6 speed.



I was wondering two things, I noticed that the gear ratios for the Dodge and Chevy are bit different. Just from looking at this website: http://www.garbee.net/~cabell/transmission.htm which shows the 3rd to 4th gap a bit shorter. All gear ratios of 1st, 2nd and 3rd are different from the Dodge version, with 4th and 5th being the same. Is there anyway to change the gear ratios on the Dodge NV4500 if as in this one case of just installing the Chevy gears?



Also I dug up this website: http://www.drivetrain.com/nv5600.html which I am a little skeptical about. They indicate that the conversion is for the 3500 only, why wouldn't it work in the 2500? Any one looked into this or have done this conversion?



Thanks;

Jim

 

[Ol'TrailDog]

Hey! Great links - I book marked them. I recently went through the same thought processes. I contacted Quad 4x4 in MT, who has a very good rep doing the conversions. Since they no longer make the NV5600 he wasn't doing the conversions anymore. I asked him about getting just the kit and scrounging up a NV5600 on my own. He wasn't over enthusiastic about selling just the kits, partly because he didn't think too much of most transmission rebuild places, with the exception of two places. He gave the states for the good rebuilders but not the names -- I sort of deduced he was recommending either Standard or Blumenthal. The main problem seems to be coming up with a decent, AND REASONABLY PRICED, suitable NV5600 from a reputable rebuilder. The yards I contacted are asking as much for a pulled NV5600 which has "only 30K" on it (funny how they all "only have 30K" on them :-laf ) as for an ebay rebuilt NV5600.



I would also consider contacting South Bend for the clutch part of the conversion. They seem to be the cat's meow in clutch applications for our CTD.



After seeing a TDR post about "someone who knew someone who" had put a GM NV4500 in their Dodge I poked around a bit. Correct me if I'm wrong, but from the table link I would make a couple of observations:

1) The GM is definately more of a 1st gear "granny" vs. the Dodge which could make starting out in 1st problematic.



2) The GM has a much better 2nd for starting out in, which would be a big plus because I hate starting out in 1st. However, with either the 255 85 16s, 235 85 17s, or the current 225 70 19. 5s I use starting out in 1st is a must unless it's a rolling stop. And this is with 4. 10s. If you have 3. 55s, 1st is a must and reverse is a joke, at least that is my experience from the 98 CTD.



3) The 3rd to 4th difference would be worse, i. e. wider, in the GM verses the Dodge.



4) All shouts US Gear splitter to me. But that is a whole new trail to hunt down.



Anyway, since my NV4500 is still functional, I ended up spending my bucks on the 4. 10s to 3. 55s project and Ricksons -- for the moment However, I know I'll be revisting this in the future when the NV4500 carps out. I'd really like to fall into, be plumb lucky, or receive a blessing and happen across a very cheap NV5600 or US Gear OD.

 

[NoSeeUm]

Yes, the GM first gear is very low, basically only a seldom used maneuvering granny. The other splits seem a bit better, especially the 3rd to 4th split.



My truck must have the 3. 55's because the rpm is about 1850 at 60 mph. I run 265/75 R16's. My 1st gear takes me to about 5 mph and I only use it to start under loads to ease the load on the clutch or for maneuvering. 2nd gear is more than adequate even starting under the loads I run with. For running empty or lightly loaded the 5 speed is almost perfect. Of course, this what I do 90% of the time.



Like I said the problem that I am try to get around is the 3rd to 4th gear split. The rpm gap is about 1000 rpm, which is a bit much when starting and then pulling a load up a hill. No problem really pulling most hills if I am already in 4th or on level ground. In that respect the gearing is about perfect.



The way I drive is I run mostly in the 850 to 2000 rpm band. Even running the rpm's up to 2500 in 3rd, the truck complains after hitting 4th gear. I believe my splits are about 1000 rpm for 2nd to 3rd, and 3rd to 4th with a split of about 500 for 4th to 5th.



I really think a NV5600 is the best over all solution. The cost for the Aux Trannies is just so close to the NV5600 ($3,000-$3,500) that it really does make that much sense. Plus all the hassle of getting it work and learning to effectively drive with it. However, you don't have to replace the clutch, which adds some cost savings, but I would likely be doing that anyway as I increase engine Hp. I believe you have to have the drive shaft shortened in any case.



But.....



I would still be nice to know if different gear ratios could be used in the NV4500 or just be able to install the gears that do the GM 3rd to 4th split.



Jim

 

[Ol'TrailDog]

I still believe the GM would have a worse 3rd to 4th ratio, i. e. 1. 71 to 1. 00 versus 1. 67 to 1. 00.



I definately agree the best option is the six speed conversion. I've had two of them and really liked them a lot. The biggest disadvantage is the six speed is a real commitment to keeping the truck long term whereas the splitter can be removed and sold seperately when it is time to sell.

 

[Jed]

The 4500 is cheaper to rebuild $250. 00 for the kit that I purchased and easy to do. I have seen posts on this site with people having trouble with some of the big rebuilders. The possibility of shipping ect. of a problem transmission makes it worthwile to find a local source that will stand behind their work. The U S Gear is the best auxiliary trans. for a manuel that tows, the Gear Vendors just has too many problems especially backing a trailer. Many have had problems.

 

[Ol'TrailDog]

A couple of other reasons to avoid the Gear Vendor is they can be used when in 4x4 and with an exhaust brake. Both important needs for me to go with US Gear -- if I went with a splitter.

 

[NoSeeUm]

A couple of other reasons to avoid the Gear Vendor is they can be used when in 4x4 and with an exhaust brake. Both important needs for me to go with US Gear -- if I went with a splitter.

I am assuming you mean can't be used with a 4x4 or E-Brake.



Yes, now I'm starting to think that maybe a good way to go would be the US Gear underdrive. At any rate it will be a bit of a while before I can install anything. Enough time to search for used ones.



Do you think that starting the US Gear in under drive, and then transferring to direct in between shifting from 3rd to 4th would work the best? Or getting an overdrive and shifting to direct at the same point? The overdrive might have some use to recover costs by by saving fuel using the overdrive when running empty.



Jim

 

[Ol'TrailDog]

Yes, that is exactly what I meant -- Thanks for the correction.



Think, fingers, think!