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Discussion Starter · #1 ·
I use my 1996 3500 during warm weather times of year for pulling my 15500 lb 5th wheel. I purchased it new and now has 84,000 miles on it. I noticed last year that when boost gets to about 12 lbs or higher in 3rd, 4th, and 5th it makes a noise like a bunch of marbles rolling around in a container. I have changed the lube two times and used the proper Castrol Syntorq. I plan on changing it again in spring before I start driving it again to see what old lube looks like and if new lubes makes any improvement. Anyone have any thoughts on what the problem could be? It is RWD with a 3.54 axle ratio.
 

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Not a lot of miles, but quite a bit of weight. It could need a rebuild. I just replaced mine this year because it got really loud constantly and I knew the bearings were about to go. It even made noise in neutral. I'm no expert though, I'm sure others will chime in.
 

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Do you tow in 5th?
 

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Discussion Starter · #4 ·
I do tow in 5th but when boost gets up to about 14 lbs, I downshift and always keep above 1800 RPM's in 5th.
 

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I can tell you from experience (I went through 12 NV4500s before my G56 upgrade) that you are needing a refresh before you have a catastrophic (expensive) failure. When they start making noise, bad things happen soon. 5th gear doesn't get enough oil to keep it cool when towing in 5th. 1800 rpm & above is 60+ mph, wind drag is worse than weight, but together will shorten the little transmission's life. At a minimum you are needing a new 5th gear because it has become several shades of blue & purple (might as well get a fully splined shaft) and all the bearings.
 

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Discussion Starter · #6 ·
GAmes, I have been reading your posts for a long time and value your opinion. I would prefer to do what you did and switch to a early G56 but at my age of 75 it would be more than I care to tackle and paying someone to do it would be more than I can spend. Is the G56 strong enough to tow in 6th gear most of the time? At the speed people drive around here, driving in 4th gear, I would be a rolling road block. So in your opinion even with the upgrade and rebuild the NV4500 still won't hold up with my weight running in 5th gear?
 

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I tow in 6th gear, but the average trailer weight I'm hooked to is about 10,000 pounds. I do tow 14-15k every now and then, but usually it isn't more than 800-1000 miles. Considering the cost, and the fact you don't drive nearly the miles I do, I suggest you just get your present trans inspected & repaired as needed. It should be good for another 80-100k. I also suggest a pair of trans coolers. I use the Fast coolers, they add about two quarts oil capacity.
 

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Discussion Starter · #8 ·
I have a Fast Cooler on one side and filter on the other side of transmission. Wife and I plan on selling our home this summer and full timing as long as possible before buying a home in a different area so will be putting a lot more miles on truck. We always take a car with us when traveling so most of the miles on truck are towing miles. I have towed the 15,500 lb. Landmark about 25,000 miles and the previous 5th wheel was about 1,000 lbs. lighter. I just looked at my records and had installed the better 5th gear nut at about 38,000 miles on odometer. At that time I didn't notice any discoloration of 5th gear.
 

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The bottom line is the trans is making noise. Better to have it repaired now then somewhere a long way from anywhere. The new nut isn't as reliable as a fully splined shaft will be. Someone on the IL page should be able to point you to a good shop in your area. It isn't logical to give you the link to Standard Transmission in Ft. Worth, other than they are an excellent source for parts.
 
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