Dodge Van rear end overheating

I have a Dodge van with a Chrysler 9.25" rear axle. It overheats enough, while towing, to melt the speed sensor. Is this a common problem and how can I fix it. This has happend before with other Dodge vans while towing.

I had a dodge and 2 ford vans, and towed a mid-sized travel trailer behind both. None of them ever overheated, but they were also equipped with tow packages. Is yours? What’s the tow rating of your van? How heavy is your trailer (not how heavy it was from the manufacturer, but how heavy it is after you load it with all your stuff)?

Van is a B3500 5.9L with a 3:90 gear. GVWR is 13,500lbs. My trailer is a dual axle Roadmaster that weighs about 5800lbs with a GVWR of 9,900. I usually carry a 56 Ford but this trip had only about 1000lbs of furniture on board. As far as I know the Van was not equipped with a tow package from the factory. What does this include? Thanks, Chuck

The max towing capacity I found for the B3500 van was 7600 pounds, and that requires the axle you have, and a 4 speed w/ overdrive automatic. I’ll assume you have that, since you have the required engine and axle.

I’m guessing that '56 Ford puts you over the towing capacity by quite a lot. The furniture bumps you fairly close to the limit, so if a trailer brake is dragging, or an axle isn’t spinning freely, it could increase the load on your van.

Did this van have the option of a Dana 80 axle. Maybe with the weight you are pulling you should consider a upgrading from a semi-floating axle to a full-floating axle

Mopar recommends an additive to the gear lubricant on all pick up, heavy duty or all used in severe conditions. Yours may be helped by an addition of a tube or bottle of the stuff.

Looking at the owners manual it has a max tongue weight of 1000lbs and a GCWR of 13,000 lbs with the 3:92 rear. Vehicle weight is 6600lbs which should allow 6400lbs of tow/load weight. On this trip the van was empty and trailer had about 1000lbs of furniture loaded directly over the axles. On the return I was carrying 1 1990 Saturn, a washer, a dryer and still no cargo in the van. Looking at this would make me think I am asking too much from this gear. I have thought about upgrading to a Dana 70 or 80 but after spending over $1000 to have this Chrysler 9.25" rebuilt I’m a bit short on repair funds. It appears I misread the GCWR. I didn’t think it included the vehicle weight.
I plan on keeping this van so how can I improve the situation? Some have suggested an aluminum rear cover with extra capacity for more heat dissapation. I would think the end all fix would be the Dana 80 rear though. Any ideas or suggestions? By the way I am running 85/140 synthetic gear oil as recommended with some Lucas hub oil as an additive. Chuck in NH

Possibly if you can get the aluminum cover with some cooling fins it may help some.

Make sure the vent is clean and working as it should

Could there be an exhaust leak?

Could the pinion gear to ring gear clearance be to tight?

Does your van use 8 lug wheels?? A TRUE 1-ton van should come with a full-floating (Dana) rear axle.

The van has 6 lug wheels and a 9.25" Chrysler corporate rear end. As I understand although it was called a 1 ton they actually were 3/4 ton. It’s a Ram Wagon B3500. The vent is clear, no exhaust problems and the ring and pinion were new this time and set up by one of the best shops in the Detroit area. This sensor melt has happend 3 times on this van now. Would a Dana 70 work or should I go straight for the Dana 80? What vehicle applications would have the right axle width and mounts? Thanks, Chuck in NH

I found a chart showing rear ends that were available on the Ram Wagon. It looks like a Dana 60 was available with a possible 4.10 gear, not sure if that would be a upgrade. If so maybe you could find a complete assembly or a hole van in a junk yard used for a conversion

The heat is from friction. Excess friction could be from dirty gear lube. How often do you change it? Also, worn bearings will cause high friction and high heat. It takes a lot of heat to melt the speed sensor. I’ll bet you have low gear lube AND a bad bearing or two.

The gear grease was new within 1000miles. I did have some ring/pinion noise on the way out that may have added to the heat. The last rearend was totally rebuilt end to end with all new parts and was filled with 85/140 synthetic gear oil and some Lucas hub oil. So those were not the problem. Chuck

The ring and pinion noise you mention is an indication of something out of whack with the rear end. Now, with the overheating problem, it needs to be addressed.

As for cause, it sounds like maintenance is not the issue. I’m wondering what kinds or roads you travel on. Rough roads or off-road is much more punishing to the rear axle, especially when loaded. I’m still trying to grasp a good reason for damage or accelerated wear.

I only use the van 2-3 times a year. Only gets about 5000-6000 miles. Usually I make one trip to Columbus, OH around labor day for the NMRA drag meet and Y-Block nationals.This trip I tow the trailer with my 56 Ford inside. Then in November a business trip to set up at a wholesale gift show in Gatlinburg, TN. No trailer on this trip.
This years furniture move was an extra one. All things considered I think I need a Dana 70 or 80 rear end or a different tow vehicle. I used to tow with a 16’ open trailer and just got the enclosed one last year.

All the troubles I’ve had over the years have all been while towing. So it would indicate excessive heat from the load. I was hoping there was some known problem with the 9.25" rear that would give me the “magic” fix.

Since this new rear end got hot enough in 200 miles at 60-65 MPH to melt the sensor I really don’t think an aluminum cover would do it.
Maybe an external cooler? Thanks for the responses, Chuck in NH

Find a Dana 60 with full-floating 8 lug hubs, brakes and all, and bolt it under your van. You may have to live without a speed sensor…

The speed sensor operates the speedometer along with the ABS brakes. So I think its a requirement. Anyone know what year the speed sensors started being installed on the rear? Chuck