Engine/Transmission (1994 - 1998) Is a NV5600 conversion worth it??

[JGheen]

So since I just recently broke my 241HD transfer case and am having a 271 case shipped to me this Friday, I have been debating selling he NV4500 and getting a 5600 since the truck is down for a while again. Problem is I not only can't find a 5600 but those who do have them are selling them for over $3K which is a little pricey for me. I also heard they are so expensive cuz New Venture gear is not manufacturing them anymore due to the Mercedes buy out of Daimler-Chrystler.

So should I just pull the 4500, install the 1 3/8" input shaft and live with it or bite the bullet and upgrade to the 5600? Just looking for some friendly advice, so let me know what route you guys think I should take.



Joe

 

[CumminsPower98]

I'm real glad I upgraded but I'm towing for a living right now. If you are not towing much you might be better off fixing up the 4500. I'm not sure what I will do when my 5600 needs work since parts are not so easy to get now. There are rebuilt 5600s for sale on ebay right now for $2,095 and up so you might take a look there.

 

[Got Smoke?]

Joe if you are that worried about it then just put the big input shaft in with a bigger hub SBC and call it done.



The only differences between the NV4500 & 5600 are another gear to decrease the large gap between 3rd & 4th, and about what guys another 100-150lbs?



I think the NV4500 will hold up just fine for what you are doing with your truck Joe, you won't be towing very much with those 37's! :-laf

 

[JGheen]

Thanks guys, yeah, very little towing with this rig. Only thing I think I will eventually tow is the sled. :-laf and maybe a friends boat or something.



Cummins98, yeah, I saw those 5600s on e-bay and that price was attractive but I am still indecisive about it.



Mark, that was the point I was trying to figure out if the extra gear is worth it but I think the larger input shaft is the way to go for the gearbox I have now. I think my decision is made unless a sweet deal comes by somewhere for a 5600.



Thanks, Joe

 

[BAnsley]

I bought a reman nv 5600 05'year model through advance auto and paid the 650. 00 for a core and still was cheaper than a wrecking yard and got it in 4 days. Accurate transmissions is the company who remans them.

 

[ALehman]

My buddy swaped out a getrag in his 93 and put a nv5600 in it. Took a little fab work, lots of measuring, and some $$ but he loves it.

 

[JGK]

Joe,



I kind of struggled with this same issue last month when I had my clutch out for replacement. I worked with a friend to who's family owns a transmission parts warehouse and he and another guy rebuild transmissions on the side. They've done 4500s and 5600s. So I did some investigation on the trade offs using them and the web as resources.



First, you have to be careful of rebuilt 5600's. Some of them are being sold as rebuilds but have barely had anything more done than a lube change! My transmission guy says rebuilding a 5600 (syncros and bearings) is real pricey. You'd likely spend $2K to have it done right. So a rebuilt for $2100 is suspect. Not saying its a scam, but I'd be wary.



I've driven a co-worker's '01 with the 6 speed. Tight, with short throws between gears. It drives nice. But driving around town and having that extra gear to go through all the time gets a bit tedious. I'm sure you'd get used to it, but I think it makes more sense for towing and getting the right gear going up grades than as a daily driver around town.



One advantage of converting a '98, your cross member is the correct one, so all you need is an adaptor plate (flat steel) and an electrical extension. Of course, you have to have the drive shafts altered (front longer, rear shortened) or maybe ones out of a 6-speed truck will work.



As to the durability, I posted a thread asking about that here 3 or 4 weeks ago. The consensus seems that 6 speeds are breaking just about as often as 5 speeds on bombed trucks. More often on rebuilts, it seemed.



Ultimately, I had my 4500 rebuilt (syncros and bearings) and put it back in. Cheapest option. I'll address the issue again some day down the road when it breaks.



Hope this helps.

-Jay

 

[CumminsPower98]

Actually the wire extention is not even needed on a '98. Mine was all bundled up and wire tied so I just cut that off and strung it back to the switch. It even had the little clip-in keepers in the right places to mount to the tabs on the back of the 5600 so it fit better than it did on the 4500. I think I would rather have my 5 speed back if I was daily driving around town like before I went OTR.

 

[JGheen]

Thanks for the info guys, its really helping me in my decision.



Thanks for that long bit of info, Jay, as I have heard pretty much some of the same things you were explaining to me about the 5600. All the pros and cons are telling me to just stick with the 4500 and put in the larger input shaft, maybe a fully splined main shaft and be done with it. I am already going to have to have the front shaft probably lengthened and the rear shortened, maybe a 1-piece 4" diameter shaft, cuz of the NP271 case coming this weekend to replace the 241HD. Probably end up pulling out the 4500, getting a double disk clutch, 1 3/8" input and maybe the fully splined main shaft. I'll let you guys know what route I go but I think the 5600 is out of the question for me since a good number of the posts I read about it tells me it is really no stronger than a 4500.



Joe

 

[Kirwin]

NV 5600 vs 4500

I have done it, and I agree with the above to a point. Its my opinion that the NV 5600 is stronger as far as brute strength. You definitely can see that the gears are larger and the OD nut doesn't come off in the 6 speed. That being said the gear splits are such that you can't skip a gear on the 5600. The torque curve of the 12 valve engine fits perfectly into the gear splits on the 6 speed. BUT if your truck is already above stock power level this is less of an advantage. You will not speed shift either transmission but the 6 speed gears definitely take longer to synchronize. If you tow heavy most of the time this makes the NV 5600 really shine, if not the NV 4500 will do all you ask of it if you fix its two weaknesses. IMHO Ken Irwin

 

[JGheen]

if not the NV 4500 will do all you ask of it if you fix its two weaknesses. IMHO Ken Irwin

I believe those two weaknesses would be the 5th gear nut falling off and the 1. 25" input shaft correct?



Joe

 

[BigBadDodge]

Probably end up pulling out the 4500, getting a double disk clutch, 1 3/8" input and maybe the fully splined main shaft.

Joe, your right on track with that sentance, just add the fast coolers for added amsoil MTG capacity and cooling



Is the rear of the 271 going to be flanged, or slip yoke?



BBD

 

[JGheen]

Yeah, Scott, your set-up was a good reason in this debate for me to stay with the 4500 since I have seen what yours has taken and it survives very well. Those fast coolers are probably a good idea especially with the extra fluid they allow you to retain.



The 271 I ordered will have a flange yoke on the output shaft. I paid $995 just like you and they had to put taxes on the price of the case but at least not the shipping. Friggin' Cali tax laws suck!

Hopefully the case will be here today and I can get it up and installed this weekend to take some measurements for the new rear driveshaft and any modifications I need to make to the front.



Joe

 

[RHARVEY]

Joe,



I would like to have (I think) the 6 speed for towing. . But what you I gain from the extra gear and how do they compare to the 4500???? Sometimes I would like to split between 4th and 5th. In some conditions its too fast for 4th but too slow for 5th. I have checked with the US Gear and from what I was told... the underdrive or overdrive is what he called a "get to" transmission. He said that he would not drive a long distance using the split between the gears. From what I understood they were not designed for full time splits... .



Rick

 

[JGheen]

If the gears in my 4500 were closer that would be nice but my main purpose behind this personal debate was for brute strength of the trans. If the 5600 had a lesser chance of breaking than a 4500, then I would really attempt to find a 5600 and buy it but I am gonna stick with the 4500 and just beef it up since they will hold up just as well as a 5600.



Joe

 

[burnin oil]

Stick with the 4500. I own both and the 5spd is definatly quicker to shift and accelerates alot better. The 6 spd is nice with a major load on it but all the gearing difference is in 4th gear and below. I have hauled approx 7k pounds with the 4500 with no problems. I havent driven the G56 yet but if I was going to convert to a 6spd that would be the one. The lower OD would put the rear gearing around the 3. 73 range. Exactly what my 12v likes.

 

[FDavid]

I miss my 6 speed. The gear ratios felt perfect and evenly spaced and had way less travel than the 5 speed. As soon as I find a nice donor 5600, I'm doing the conversion.

 

[scramblin]

Joe,



As to the durability, I posted a thread asking about that here 3 or 4 weeks ago. The consensus seems that 6 speeds are breaking just about as often as 5 speeds on bombed trucks. More often on rebuilts, it seemed.





-Jay

I have almost 50k mi since my conversion. The best thing I have ever done. Oo.

 

[JGK]

I didn't say the conversion doesn't work. I just didn't have anyone say they'd trashed several 5 speeds but had not been able to break a 6 speed doing exactly the same thing at the same or higher power rating.



-Jay

 

[Vaughn MacKenzie]

I miss my 6 speed. The gear ratios felt perfect and evenly spaced and had way less travel than the 5 speed. As soon as I find a nice donor 5600, I'm doing the conversion.

I'm with ya David. After owning two of each I much prefer the 6-speed, even for city driving. I find on my '96 I'm always driving at "limbo" speeds where I'm dead between 3rd and 4th gear. So I have to run the RPM up or lug it a little. It seems I actually shift MORE in town than I did with my 6-speeds!



Since the NV5600 seem to be getting more and more scarce I am hoping someone will come up with a G56 conversion. I'm sure that transmission is quite spendy but it seems to be proving itself quite well. With the 3. 54 gears of the 2nd Gens the top gear shouldn't have the motor spinning over too fast, and I would like a slick-shifting transmission.



Vaughn