Engine/Transmission (1998.5 - 2002) upgraded NV4500's questions - 5th gear problems

[JAlford]

For the 2nd time, my '99 3500 is down, broken 5th gear, lots of metal in fluid. This time trans was fully rebuilt 12K miles ago. Previous time, I got 50K before failure, metal in fluid caused brg failure. Original factory trans had 93K when 5th gear broke. I do change my fluid every 15K to 30K.

This truck is not used in competition, only tows my 11,500lb camper 4-5 times a year, and otherwise is a daily driver. Engine is modified mildly (see sig below).

How many 2nd gen 5spds are towing in this range, and how many have converted to 6spd? Those with conversions, are you happy with results? 5spd users, have you had to rebuild multiple times?

Thanks for the input.

Jeff

 

[surfbeetle]

Mine has 192,000 miles on the original factory NV4500. Just did the first clutch at 185,000. My Fifth wheel is also 11,000. I tow a fifth wheel with a utility trailer on behind the 5ver as well. I think that wear on these things is a function of how it's driven.

I NEVER use fifth gear below 2,000 rpms and I never lug the engine in any gear. I always keep the rpm range up. If I am at a speed that either fourth or fifth gear can be used, I stay in fourth gear, especially when towing. I do tow in fifth, if the speed is high enough to keep the rpms above 2000.

I used to have a 4. 10 rear end, now I have the 3. 54. As for trans oil changes, I have changed my oil 4 times over the last 14 years and 192,000 miles. Including the factory fill, that averages to be every 38,000 miles. The last three oil changes have been royal purple. The first oil change was valvoline. I never have used the castrol other than the factory fill.

I realize that this does not help your current situation, but I just wanted to share what has gotten me to where I am at with my nv4500.

 

[ewcmr2]

I replaced/rebuilt my NV4500 twice before converting to the G56 six speed. Almost all my driving is away from home with my Gooseneck trailer so I wasn't going to keep the NV4500 knowing it wasn't up to handling my demands.



I've only have about 20k on the G56 so time will tell if it's going to hold up. The smaller gaps in between gears is great when towing. If driving empty I skip gears.

 

[JAlford]

Surfbeetle - I'm curious as to your hp and torque output, if you know it. Also, your fuel mileage.

Reason for asking, most rebuilders I have talked to other than Standard Transmission tell me that the limit on the 5 spd is 500 to 600ftlbs and about 275hp. I am considerably above that, need it to be able to tow in the mountains, where we do most of our travels.

Also - do you do most of your towing at low altitude?

Jeff

 

[surfbeetle]

JAlford,

I'm at sea level but have taken trips up to Lake Tahoe. I have climbed the grapevine on I-5 many times. We have a campground membership here in the local mountains at about 4500 foot level and we go several times per year. As for horsepower, I have a 12 valve with the number 5 plate, so 600 ft pounds and 300 hp is probably about right. My stock clutch would slip if I wasn't careful. I have a valair clutch now, doesn't slip anymore. Mileage empty with the 354's is 24 at 70 mph. I don't know towing mileage.



If you are considerably higher than the 275-300 hp and 600 ft lb range, you may very well be better off switching to another model trans. Keep in mind that the nv5600 is also hard to find parts for.

 

[timbo]

I just got mine back together. Mine was the same thing again, broken 3rd on the countershaft. I got 20k out of it before it broke the second time. I'm not real big on the 6sp since I do alot of town driving. I just don't want the extra shifting. If I towed everyday it would be a great solution.

I'm with surfbeetle, keep the RPM's up and stay out of 5th below 2000rpm.

I also had to replace the clutch disk due to broken hub springs. I went to an "O" disk instead of the "OFE". Also I'm going to pull my stage 4 injectors and drop them back to. I'm not going to make a career out out pulling my trans every 20k.

https://www.turbodieselregister.com...218102-nv-4500-3rd-gear-broke-again-help.html

 

[JAlford]

I talked with Midwest Transmission yesterday late, and they are offering all Cryogenically treated parts for the 5spd. They say that it will take the extra power and torque to make the unit just as strong as the 6spd, as it is supposed to increase the strength of the parts by 25%.



If anyone has some experience with this setup, please post your opinions. I am now comparing this setup to the conversion to the 6 spd, and from a cost standpoint it is a real money saver, half the cost for parts and much less labor. Unfortunately I am not really in the position to play test subject, so looking for some experience.



I estimate that I am towing with around 375-400hp to the ground, 750-800ft lbs of torque, when in the mountain passes. I do almost all of my driving below 2200rpm. Due to the setup of my aftermarket parts and this particular engine, it looses all of its power at 2500rpm and my EGT's climb through the roof above 2400rpm, so I don't have the option of keeping the rpms above 2000 with the 5spd. I do try to stay between 1800 and 2200 if possible, as it makes a huge difference in my fuel mileage. I tried towing only in 4th, which limits me to a max speed of 57mph before the EGTs get to 1300degF, and my mileage dropped from 11-12mpg to 8-9mpg. Needless to say, out west 55mph is not a safe speed anyway, with traffic whizzing by at 80.

Jeff

 

[timbo]

I talked with Midwest Transmission yesterday late, and they are offering all Cryogenically treated parts for the 5spd. They say that it will take the extra power and torque to make the unit just as strong as the 6spd, as it is supposed to increase the strength of the parts by 25%.



Could you give me the phone # for those guys. I never even knew about them.

 

[JAlford]

timbo - see link below

Midwest Transmission Center

I talked with one of the owners, and he told me that they have a lot of "hot shot" drivers who are using this setup, towing at a combined truck/trailer wt of 20 - 25K. They seem to be getting 50 - 100K miles between rebuilds, or at least that was what I understood.

I did some materials engineering classes 20 yrs ago when I was getting my ME, but I haven't kept up with the process. I may call their Cryo parts treater to see what they have to say.

The only problem that I see with it is that you cant Cryo certain parts, the bearings being one of them, or at least that is what I am assuming, due to the bearing design and that it is already assembled. And also, it doesn't help keep the 5th nut in place, either. Midwest has their own special design for nut retention, and from a design standpoint it sounds failsafe, as it doesn't allow the nut to be loaded, uses keepers instead. They told me that they had not had any 5th gear nuts back off with that design.

Jeff

 

[GAmes]

They seem to be getting 50 - 100K miles between rebuilds...

With Standard Transmission rebuilds I normally get 80 to 120k miles, so that doesn't sound like much of an improvement to me. I have got two from them that lasted less than 10,000 but they paid for shipping and labor, one in Oregon the other in Arizona. My personnal 5er weighs 13,000+ and I sometimes tow a trailer behind it. The trailers I pull as a transporter are usually in the 10,000 pound range. Some are heavier and some are lighter, but 60 to 70% of my miles are towing something.



I have a transmission temp gauge and I have found that the temp shoots up when pulling in 3rd on a steep climb and 5th gear all the time. Both gears are driven by the countershaft so my theory is that the load on the bearings creates more heat than the oil can carry away. OH yes, I do have Fast coolers. When the first transmission failed the 5th gear was blue fron getting so hot. I normally drive at 1900 rpm and since then I never exceed 20 pounds of torque in 5th and have gotton longer service out of my rebuilds since then.



With the help of ewcmr2 I am in the process of converting to a G56. I expect it to last a lot longer than the NV4500. They just were not made for hauling in overdrive and 4th gear is too low for highway speeds.