I've done some searching and haven't really found exactly what I'm looking for. I have a 99 Blazer 4d 4wd. My family and I are looking for a camper but I want to make sure I don't buy something that is to heavy for this vehicle to tow. We borrowed a pop up camper this weekend and towed it about 130 miles each direction(house to campground and back). During the trip I kept it in 3rd gear as we were driving on some hilly roads. We were fully loaded in the back with coolers and camping gear, the camper was loaded down to a total of around 1 ton gross weight and we also had a full cargo carrier on the roof rack. I have a scangauge II and had it setup to monitor tranny temp as well as several other temps. We did the trip in 85-90 degree weather most of the way. During the trip the tranny temp varied from 190-220, with the higher temps being when we were going through hilly areas. The previous owner told me the truck had the heavy duty towing package from the dealer which he said included a lower gearing, the wiring, hitch, and tranny cooler(I have not confirmed this exists, I can't see it from the front). I have what looks like the feature list from the bill of sale at the dealer and it lists:
Heavy Duty Trailering Equipment
Rear Axle - 3.73 Ratio
4 Speed Electronic Transmission with Overdrive

I was hoping someone with knowledge of towing with this vehicle could step in and tell me what they think would be the maximum weight that it would be safe to tow with this truck along with some insight into if those temps were two high or if they were ok. The engine temp remained constant the entire trip around 207.

I'm including a picture below fully loaded, dunno if it will help or not.

 

The factory rated trailer weight is 4000lbs, but if the trailer is a lot wider than the Blazer, I find that the wind drag affects it as much or more than the weight of the trailer. The factory transmission "cooler" is part of the radiator on the Blazers. If you're going to be pulling a heavier trailer a lot you might want to invest in an aftermarket cooler as it will be way more effective.

If you're pulling a trailer that is close to the factory rated weight and have a heavily loaded truck too I'd suggest that you seriously look into a trailer brake system because it will definitely affect your braking distances.

 

I felt the difference in braking but it wasn't terrible, I did several test brakes on the highway to get used to it. Does anyone have any comment on the tranny temps I was getting while towing?

 

Those temps don't seem bad but I would probably still look into upgrading to a larger aftermarket trans cooler. If you intend I. Doing regular towing its a minimal investment to protect your tranny

 

the transmission is actually cooled by the coolant
In a perfect world it would always be the exact temp as the coolant but lets be realistic
I you add a cooler make sure it loops threw the coolant on its way back to the transmission otherwise in cold weather it will over cool

 

I'm not quite sure I understand what your saying, if I add an aftermarket cooler, (I'm looking at the B&M Plate Style Transmission Cooler) would that not by cycling the tranny oil through the cooler, how would you loop that back through the coolant?

 

You are talking about a Plate that acts as a heatsink that you add to the belly pan OR it replaces the Pan. We are talking about a trani cooler that it literally a small radiator and it Plumbs into the Transmission lines that run to the front of the vehicle and currently run through the Coolant Radiator..
Here is a pic of one I put on my Jeep. In my case I did not run it through the coolant radiator.
My feeling is tranis like to run ' the cooler the better'. The Jeep has trailered my 20' boat for over 15 years with this setup.

 

Tony H in Winter cold, you can cool the tranny too much. It never warms up properly.

 

Ok so let me see if I have this straight.

Two kinds of cooling - Using the engine coolant running through channels in the tranny or cooling the actual oil in the tranny.

Currently the only kind of cooling that is being done is with engine coolant.

If this is true then my next question would be is this a closed system with coolant running through the tranny and part of the radiator only or is it all shared and does all the same coolant run through the engine, tranny, and radiator? If the latter is true then adding a secondary cooler would also cool the engine more?

What is the preferred method of cooling the tranny, cooling the coolant or the oil? It would seem that since it's already being cooled using the coolant that cooling the oil as well would be a more affective addition? However if there is a concern about over cooling it how would one deal with that with a oil cooler, simply bypass it in the winter somehow? I see on the website for B&M that it may be able to handle this on it's own by preventing thicker oil from entering the cooler.

Thanks

 

The coolant never goes to the transmission. Theres lines that run from the transmission to the radiator that carry the transmission fluid to the radiator. There are two plastic tanks (one on each side of the radiator) one is for the transmission fluid and one is for the engine oil. (the plastic tanks keep the transmission fluid and the oil separate from the coolant.) The radiator cools the coolant, cools the transmission fluid, and the engine oil. (Again, coolant never actually touches the oil or transmission fluid.) The only trouble with that setup, is that when you are towing, the transmission may get a little too warm, and the stock radiator just won't be enough to cool the transmission fluid as well as an aftermarket tranny cooler setup that is dedicated to cool ONLY the transmission fluid. I hope this helps.