1999 Blazer, 4.3 6 cyl, 4x4.
My transmission is not doing good (normal running temp is 215, up to 250 if hauling), I can feel it having issues so I will need to do something about it in the next 2 months. I have had this transmission rebuilt about 5 times since I had this vehicle since 2002. Seems I have caused all the problem by hauling without a transmission cooler and not doing the fluid changes Im sure have made it worst.

Anyway, I will either rebuild it myself or replace the transmission. Seen the videos and it is not too complicated and since I do all my mechanic work I am sure I can do it fine.

In the other hand, if I can get a newer used transmission I might be better off tiemwise (im installing that transmission cooler this weekend) so I am trying to find out what do I need to look for in the donor vehicle. I know almost any gm that is rear drive, (at least from 1993 but I will look for later models) will have this transmission. If the vehicle has the 4.3 I think there would not be much changes, just trying to make sure I dont pull the wrong transmission, I know the bell might be different where it attaches to the engine might be different but my understanding is that the rest of the transmission is the same and the bells can be exchanged. I am assuming the electronics connectors are still the same, but you know what they say about assuming...
I could just look at blazers for a straight change but I think they stopped making them on 2002 and I would like an later model so the transmission has more life left.

There seems to be 3 options for hooking up a transmission fluid cooler. Install the cooler and ride the lines to it excluding the oem cooler.
Install the cooler inline with the oem cooler but having the aftermarket cooler in the IN side of the oem cooler.
Install teh cooler inline with the oem cooler but having the aftermarket cooker in OUT side of the oem cooler.
Which method offers what pro/cons?
And since we are at it, which line is the in and which one is the out?
Is there any way to avoid cutting in the aluminum lines, some sort of kit?
So far I have looked into the Impreial 243012 kit from Advance, any other cooler? I would not mind waiting on the cooler if I can get a better option (time vs price).

I have thought about doing all the install needed including cutting the lines (if that is the only resort) but not actualling hooking the cooler so I don't get any old bad transmission oil in it. Will it really matter?

Lastly, is there some sort of flushing kit that can be installed to the oil pan to make it easier to change the transmission fluid? Taking the pan off is such a mess....

Thanks y'all!

 

Wow, good luck. It doesn't help you directly, but I upgraded the cooler on my '99 Yukon with the 4L60 with a B&M 70266 from Amazon. My rig already had the factory transmission cooler so this was almost a direct swap. I did this because my wife, our dog and our 27' travel trailer made a trip from CO to ME this past summer. We had two additional passengers on the way back; my wife's 91 year old Mom and her 43 year old niece flew into Maine and rode back with us.

The cooler definitely did the job. The transmission never went above 220 or so, even through the mountains of West Virginia. If I ever add a cooler to my 2002 Blazer, it will likely be this one.

I wouldn't put any faith into a used transmission, especially one from a salvage yard. It is just too easy to burn one of these things up. When my Yukon is ready (178k original miles), I'll be taking it to a reputable shop and having some upgrades done to it for towing purposes. We're taking our travel trailer to CA this summer, and I'm trying to decide if I should preemptively get it rebuilt. It doesn't give any indication of failure, but I don't want to have us all stranded.

 

The proper way to do it is run the tranny fluid lines through the radiator cooler as normal and take the return side and run it to the external cooler then back to the transmission. There is no such thing as too much cooling with an automatic. You must make sure your radiator cooler is not leaking, blocked or dirty first though., Also if you are hitting those types of temperatures i ,would definitely make sure the engine cooling system is all functioning properly. The temp should never get too 250 even under load. Maybe add an electric fan to the front of the radiator for extra cooling.

 

Thanks for your input. The motor temperature will stay between 188 and 197 when the temp goes up if my memory serves me well.

 

in the radiator, which line is the one with fluid coming from the transmission? I rather not have to manually test that....

 

If memory serves me right.....the bottom line is the feed from the trans & the top line is the return........ btw., I would just bypass the radiator completely! I installed my aftermarket cooler this way, cut the ends of the lines off, and run the rubber hoses to the external cooler......why do u want to leave the trans fluid running through the radiator? Think about it.........how warm is the coolant in your radiator? 195-200 degrees, now what is the biggest destroyer of transmissions? - HEAT.....need I say more?

 

Yes the right side or passenger side of the radiator is the trans cooler side.

 

Think about it, the coolant is at engine heat level on the side that the coolant enters the radiator. On the other side where it leaves the radiator is should be cooler, how cooler, I really dont know but I will check when possible. I bet the difference is noticeable but I also suspect it will be very dependent on weather. At least in my blazer the cooler is in the passenger side of the radiator which happens to be the cool side.

I decided to run in in series with the OEM cooler to help with the transmission warm up. The fluid will go to the OEM cooler then the aftermarket cooler. That way when the car is parked and not moving while warming up the aftermarket cooler wont cool much but once I start moving it will help. During summer time I might feel different but I am not wanting to drive a cold transmission neither I want to be in the cold parking lot a minute more than needed.

I got the cooler in place this past weekend. I connect everything but the hoses to the new cooler. I not sure I want to run this transmission thru it until I do a flush, then I will decide if I will or not...

Why doing a flush?....

Lucas Transmission Fix... I thought this was "snake oil" but Lord... It does work... First thing it did was to make it shift back to normal, it also dropped the temperature down by 10 deg... So I think if I flush and change the filter I might get a few more months out of this transmission. If the pan dont look too horrible then I will add the cooler. I will rebuild the transmission either late spring or early summer....

 

Trans fluid enters the top fitting on the radiator, just like engine coolant. The OEM cooler is in the side tank of the radiator. It's a coiled up tube, (looks like a spring) and is submerged in engine coolant. It does NOT go through the core of the radiator. The fluid exits the OEM cooler directly below the inlet. As fast as the fluid passes through it, it's amazing there is any heat transfer at all!


"I decided to run it in series with the OEM cooler to help with the transmission warm up."


Running 215F to 250F, it doesn't sound like it needs any help warming up If you eliminate the OEM joke cooler, the 243012 cooler will maintain trans fluid ~60F above ambient, and you won't need any "snake oil", just DexronVI, which is what is recommended. As mentioned, heat kills transmissions, the cooler the fluid is, the longer the trans will last.





EDIT: When the cooling system and transmission are operating properly, it can take 20 miles or more, for the transmission fluid temperature to equalize with engine coolant temperature.

 

Im aware of that but I appreciate you taking the time to go over it, some might not.

The 215 to 250 degrees are not while warming up the engine while on park. Actually, after adding the "snake oil" (lol) the transmission would not go over 194 deg under normal driving which would always be over 200. Heck, it barely made it to 180 on my drive to work and we had 55 deg weather today.

Thanks everyone for your input, I will be experimenting a bit further.