Engine/Transmission (1994 - 1998) NV5600 question

[SRehberg]

I see where others have converted to the NV5600 in place of the NV4500. Is there a benefit to this swap, i. e. are the gears closer together through the range, not just a lower first or something like that. I have a '96, is it a reasonable swap and do all the years of NV5600's fit if 4X4 or whatever it goes into? My NV4500 has a pretty wide spacing in ratios between 3rd to 4th etc. The GV OD is in my opinion not worth it and will come out. Thanks

 

[CumminsPower98]

I guess it depends what you like and how you will be using the truck. It's much better for towing as the gear splits are more evenly spaced and not so wide. It matches 12 valve quite well. It's not much good for racing or anytime you want to speed shift. I am really glad I have one in my '98 now as I'm towing about 45% of the time running OTR delivering RVs. If I wasn't towing a lot I suppose I might like the 4500 again. It was a real easy swap in my '98. It's also pretty easy in '97 and older but not quite as easy. See my mods page below for details on my swap and also some info on older trucks.



See this thread for lots of talk on the same topic:https://www.turbodieselregister.com/forums/showthread.php?t=165277

 

[wildmanben]

bad thing about the 5600 is that parts are becoming extinct

 

[SRehberg]

CumminsPower98, thanks for the information, I will go to the reference you indicated. I carry a 5000lb + camper most of the time, so the truck is working a lot. The gear spread with the NV4500 is pretty tall between 3rd to 4th.



Wildmanben, so parts are going to be an issue in the near future, something like the manual transmissions of earlier years?



I have a GV OD which is pretty useless, as 4th over is like stock 5th minus a 100rpm. 3rd over is a split but the rest is un-useable basically as 5th over is to high except for absolutely flat running. I like the idea of a more evenly spread set of gears, but if parts are going to be a problem? Is it any better for parts going with the NV4500?



Thanks for all the help.

 

[hsmith]

I agree that 4th over is almost the same rpm's as 5th, but you have the strength of 4th gear for towing. For me, the GV is a plus for towing. Hard to justify the cost though.

 

[SRehberg]

I guess what I don't like about it is the fact it seems to be hard on the drivetrain. What I mean is coming in and out is no fun as matching the rpm so there isn't a big clunk is tough, especially in a hurry. Say pulling a hill, you want to go from 3rd to 3rd over, it's such a lag inbetween you lose speed fast. If you forget to go to neutral or match rpm in a panic stop it almost feels like you've been rear-ended because it disengages at 20mph +/- and being in gear, it tries to speed up the engine/trans. If I'm in a near panic or a panic stop, I'm not concentrating on trying to match rpm's etc. It seems to be forceful enough I am concerned about the hit the transfer case or trans takes. Maybe it's just me. I agree 4th over is a strong gear. If I go to 5th it's almost the same. 5th over and the truck can't pull it on anything but the flat, so no good there.



I'd like to be able to divide up the ratios a little better than the 5spd has, so hence the interest in the 6 spd.

 

[MFrenchek]

I don't have that problem with the US Gear unit. Third-high is a nice split between standard third and fourth. No loss in speed just a little clunk as the aux kicks in real fast and I just keep climbing. No issues on stoping, down shifting or using the exhaust brake. Nice split between 4th and 5th.

 

[hsmith]

Don't have the problem with rough shifts. Did take a little practice to make them smooth. One disadvantage of the GV is it should not be used for braking. When mine is engaged, the EB is disabled, and vise-versa. The US unit does not have this problem, but may be more prone to rough shifts, though I have not had any experience with them for many years.

 

[wildmanben]

if you check out quad4x4.com or standardtransmission.com, both have noted that parts are getting harder to find and more expensive also. The 4500 is here to stay though.

 

[SRehberg]

hsmith, I use the exhaust brake with the GV, otherwise it's no good to me. So it's not to be used with the exhaust brake? I carry a lot of weight and can't imagine going down a hill w/o the brake but it's still fast enough I don't want to run direct. I guess US Gear must use a different system than GV as they use hydraulic pressure to keep the clutch engaged, hence the drop out at low speeds. Sounds like US Gear has a better design.



I wonder why the parts for the NV5600 are getting harder to get, not that many made? The NV4500 has been around for awhile so maybe the better parts availability? Is there any gears that can be changed in the NV4500 to help with 3rd to 4th?



Thanks

 

[JGrover]

Unless you drive really slow. I think you will miss your GV

I pull a 9k boat up some big hills. 4 hi 65mph@1900rpm 1000/1100 egts

Keeps the load off that 5th gear nut.

5hi 65mph@1600rpm and 80mph@1800rpm My fwys are usually around 75mph

I sure hate it when you leave it in 3hi and drop speeds down to 25mph. It slams a downshift :--) :{

I went with the GV over the us gear due to the fact they say it cant leave you stranded. It just wont go into OD. What I dont like is,Very inconsistant shifts. Smooth when cold,Rougher when hot and Shift speeds change with vehicle speeds.

 

[JGrover]

CumminsPower98, thanks for the information, I will go to the reference you indicated. I carry a 5000lb + camper most of the time, so the truck is working a lot. The gear spread with the NV4500 is pretty tall between 3rd to 4th.



Wildmanben, so parts are going to be an issue in the near future, something like the manual transmissions of earlier years?



I have a GV OD which is pretty useless, as 4th over is like stock 5th minus a 100rpm. 3rd over is a split but the rest is un-useable basically as 5th over is to high except for absolutely flat running. I like the idea of a more evenly spread set of gears, but if parts are going to be a problem? Is it any better for parts going with the NV4500?



Thanks for all the help.

Sounds like you need more power Maybe #11 plate

 

[SRehberg]

JGrover, I'm running 4. 10 gears so when I hit 4th over the rpms start to go up fairly quickly at freeway speeds. I'm seriously thinking of changing the gears to 3. 54 or 3. 73 to help, but then 5th over would be pretty high. I see your RPM is pretty low in 5th over with the 3. 54 gears. I'm already to high geared in 5th over except for extremely flat running.



I'm one of those that hates to alter stock things, so I'm reluctant to change plates etc. With stock I don't have to worry about excess EGT's etc or popping a head gasket etc. Paranoid? Probably LOL.



Do you know if the GV is or isn't approved for use with a exhaust brake? I'm running one and it seems to work fine, but that could be a disaster waiting to happen if it isn't designed for it.



I had thought the NV5600 would be a good trans choice but with parts getting hard to get, it wouldn't be a good idea it seems. I doubt very much the previous owner of my truck fixed the 5th gear nut, so is there any warning, i. e. sounds or anything?



Thanks

 

[R C Cola]

Warning ?

When 5th gear comes loose on mine there was almost no warning. Felt a little funny and a minute or 2 later gone. You can fix it in the truck. Just pull the tail

housing off. Oo.

 

[GAmes]

At Standard Transmission in Ft. Worth you can't get a 5600 without a core. Core charge is up to $1000 and a rebuilt unit is $3000, twice that of a 4500. Add in the other mods (flywheel, clutch, press plate, driveshaft, etc) and you are looking at a very expensive added gear. Parts availability from what I've heard is only going to get worse. I'm wondering how hard a G56 refit would be.

 

[hsmith]

SRehberg,

How many miles have you used it for brakeing? I shelled one at 60k and they told me it was because I used it for slowing down. I usually pull 14k plus and now do not use it at all for slowing down. When I have the GV engaged, the ground for the EB relay is interrupted, and both will not be energized together. Working good so far. Oo.

 

[SRehberg]

hsmith, I have had the exhaust brake on the truck for about a year. One trip to Canada and back (2200 miles) and the brake was a necessity. So yours went south after 60K due to the EB use? I'm not so sure the GV OD has any advantages other than on the flat. Sometimes I'll be on a highway where the speed is 70 or so and a grade appears requiring the brake. With 4. 10's I'd rather stay in OD but I guess that's not the case?

 

[CBorzoni]

I have a nv5600 with a gear vendor overdrive unit. I have 3. 73 gears in the rear end but i like my gear vendor unit so far. I just replaced it though as the prevoius owner who had it installed the gear vendor and set up the end play wrong gear vendor say there should only be 0 to . 015 woth of end play on the coupler. When i check it there was . 250 thousanths! which in turn broke the bushing on the front of the gear vendor which stopped the oil pump from turning burning it up! I Still made it homew though 350 miles. I like it but we'll see about its longjevity they say it is rated to 30,000 lbs and should go 250,000 miles? It does come out of overdrive very hard i will try it in nuetral though to see if it helps. It is a great freeway flyer unit and it does tow great up steep hills in 5th od. Gear vendors says DO NOT use with a exhaust break and do not tow in 6th od if you want to tow with it in od you have to tow in 5th od. Hope this helps.



Chris Oo.

 

[SRehberg]

chris, I appreciate the information, but by removing the ability to use the exhaust brake while in OD, whether 4th over or 5th over for that matter, it really eliminates the attractiveness of the unit. How did you measure the end play of the coupling, where it attaches to the transfer case? I have no idea what mine is, as the previous owner had the unit installed.



I would think with 3. 73 gears or 3. 54 gears, the rpm's in 6th over must be pretty low! I'm really close to changing the gears to 3. 73 or 3. 54 and getting rid of the GV unit so I can enjoy the benefits of 5th and use the exhaust brake. You know how it is, nothing money can't cure! Now all I need is some.

 

[CBorzoni]

If i were you i would call gear vendors and ask them about your exhaust brake

question. On the replacement install instruction given to me with my reman unit it states " Do not operate G. V. under 20mph in the manual mode. Do not use for engine braking when going down grades and gearing down. If you have an after market Exhaust brake it MUST be off When the GV is on it also says an Auto lockout is available through gear vendors. This is from gear vendors sheet supplied to me. As far as the coupler end play if gear vendor installed it i would not worry about it . If you want to check your play then you can pm me and i can forward the instructions to you. I like the unit as i can haul ***** on the freeway and still get good fuel mileadge. I do not know what rpm i am turning but it is super low to give you an idea i cannott even go into 6th od until i am going atleast 70mph them the truck wants to cruise at almost 80 mph it seems real happy and i don't even hear or feel the motor. Oo. Oo. It is a different story when i am towing i slow way down i cruise at about 65mph on lighter loads in 5th od it's perfect for me.



Later, Chris