6 Spd gets hot and stuck in gear

[JScherer]

I have a 04. 5 3500 6 Spd Manual and tow a 15K+ trailer. I have a growing transmission problem of running 75mph (the speed limit in NV) and running for 2 hours plus, then hitting a grade and needing to downshift to 5th and the shifter feels like it is bending as I push on it. Then, once in fifth, it doesn't want to come out unless I really yank on it. I got out in the heat the other day and sprayed my water bottle just to see how hot it was and the case has turned almost a brown rust color and the water beads off so fast it makes noise. There is no doubt it is overheated. Just to reference I checked the rear end with the same test and it is still something you can touch with your hand. I have changed the fluid with Redline MTL once at 40K miles and then last time at 75K miles I put the stock stuff back into it just to see if it was better. They all net the same results, it has been much worse lately, but also a lot hotter outside. When I'm not towing or towning at night in the cold, shifting is a breeze. Truck is stock, no chips just exhaust and AEM air intake. EGT's run 1200 when cruising and 1500 when pulling hills. Trailer is tall and has a fair bit of wind drag. Truck is at 75% throttle to maintain speed.



Any ideas would be helpful. I searched quite a bit and agree that a Fast Cooler might help, as well as overfilling. Can someone explain if the overfill just adds capacity or if the level is helping to lube parts that are up high. I need to get this thing working as I have a few long distance trips coming up next month. Thanks- Jason Scherer

 

[klenger]

Me thinks you have a clutch problem, not a transmission problem.

 

[jwilliams3]

I would also over fill the level by a quart so that the fluid level rises in the gear system or the equivalent if you have the fast coolers.

 

[Cattletrkr]

The brown rust color is normal... I think. Both my NV5600's were rusty from day 1.



You may want to go buy an infarred thermometer or whatever they're called and check the temp. Maybe a transmission temp gauge too.



Mine gets hot, but I don't think it would sizzle water. I've got the fastcoolers and I overfill by 1/2 qt. or so.



Now that I think of it, the "bending" lever sounds familiar. Mine has done that a few times, but it's never been bad enough for me to think it's a problem.

 

[tkerrigan]

I may be mistaken, but isn't Redline MTL (90 wt) too heavy for a six speed. I believe that it takes 30 wt. If 30 wt is required, 90 wt may have burned the bearings?

 

[JScherer]

Cattletrkr: Did you tow with yours before you got the Fast Coolers? Thanks for the response.



I ordered a Fast Cooler today to see if it cools it enough to fix the problem. I will also add an extra quart in addition to the two that the cooler will add.



I'm just suprised I'm the only person who has a NV5600 that overheats and won't shift when it gets hot? I know I push hard but would think that many of you push at least that hard with all the extra power so many of you guys have.



The clutch is fine, that would be a bigger problem at a stop going into gear. It happens only after an hour + in 6th at 75+ then the lever feels like it bound in the gear and throughout the motion feels like the oil is harding into epoxy.

 

[steved]

I may be mistaken, but isn't Redline MTL (90 wt) too heavy for a six speed. I believe that it takes 30 wt. If 30 wt is required, 90 wt may have burned the bearings?

No, the MTL is the correct oil for the NV5600, the MT-90 is the heavier weight oil for the NV4500 (not for the NV5600)... I'm running MTL in my truck. I had the exact symptoms you described (shifter hanging, but no overheating) with Royal Purple, but the MTL took care of that...



Oh, and another thing... water boils at 212*F at sea level... and significantly less at higher elevations... my transmission runs 230* when running almost empty on a hot day at any speed near 70mph. So watching water boil off the transmission wouldn't be out of the norm... I could do that with mine running empty... it really doesn't tell you anything.



I would say change the oil out again... for MTL or some other synthetic (besides the OEM) and try it again... see if it clears up... may need to change your fluid more often. I bet it is the oil (or contaminants in the oil)...



steved