I bought a 98 4x4 with the 4.6 and 4R70W for cheap ($250) with 177K miles to use now and then. The trany runs fine except it overheats on the highway (OD light flashes). I was going to change the fluid and filter this weekend and install a trans cooler just to keep it from overheating (on a tight budget on this truck and don't want to rebuild the trany). The truck has the towing package trans cooler but the one I bought is bigger. Has anyone ever installed the cooler in series (both coolers connected). I know this would overcool the fluid in the winter but again I won't be driving it all that often. Will connecting them in series restrict the flow too much? Should I just install the new one?

Thanks,

 

Series is how most are installed. Anytime changing the fluid and filter is a good idea, especially if yours is running hot. You should have a converter drain plug so you can drain more of the fluid out.

 

O/D light flashing does not necessarily mean the fluid is overheating. There are a number or possible problems that it could be. Best bet is to go to the dealer or a trans shop that can properly diagnose the issue. Adding extra coolers at this point would be like putting a Band-Aid on a gunshot wound.

 

I know I could go to a trans shop for a diagnosis but again I only paid $250 for this truck and just replacing the fluid and filter has blown my budget. It would cost me over $100 for a diagnosis. I already bought the trans cooler. I am looking for a bandaid. My question was, can I put the two coolers (three if you count the radiator cooler) in series or should I just replace the factory one with the bigger one I bought. Is putting them in series going to reduce the flow too much? Again by no means will this truck be a daily driver (maybe 750 to 1,000 miles a year) and it has many additional problems, I am only trying to be able to get it to the point where I can drive it on the highway without overheating the transmission. If the transmission goes in a year or two, I will worry about replacing or fixing it then. I am going to install the cooler today. Let me know if putting them in series is a bad idea or if I should just replace the factory cooler.

Thanks again for any help.

 

Auxillary transmission coolers are just that. They are designed to be hooked up in series (not replace) the factory cooler. If you were going to replace the factory one, you might as well not even bother with the auxillary cooler as the end result would be the same. I don't think that another cooler is going to give you the results you're looking for to be honest. They are made to keep the trans at normal temps under high stress situations like towing.

Let us know how it works out, although I wouldn't be surprised if the trans gives up the ghost before a year is up.

 

If your trans is overheating in OD, then it probably means that the TC is not locking. Adding an additional cooler won't necessarily help much...

What kind of cooler is it? Is it a 'tube and fin' cooler? If it is, just because it's 'bigger' does not necessarily mean it's 'better' then the stock one... Those kind of coolers need a lot more surface area to achieve the same cooling as the smaller 'stacked plate' coolers..

I understand your economy reasoning on this, but I've also heard that it's not good to put coolers in series on some transmissions because it does lower the fluid pressure in the trans..

There are other guys on here that are true trans gurus and hopefully they will chime in to help you..

Good luck!

Mitch

 

This is good info, and I've also heard that only one aux cooler should be used (in addition to the tank cooler) for the same reasons.

Andy