Auto trans cooler....wow
 

Ok, I thought this would be big but it is a little smaller than I thought. The transmission coolers on AWD turbo automatic eagle talons are double this size on a 4 banger![verymad]

But it is thicker than normal.

Don't forget, thats not the only one. There's a water to oil cooler on the passenger side below the turbo.

What is the diameter of the tubing on that cooler? Many a CTD automatic transmissions have been burned up by well-meaning-unknowing owners, the tubing on our trucks is 5/8, you don't want to restrict the flow with smaller (3/8) lines. DTT recomends Tru-Cool brand oil cooler, might want to check it out. Last time I checked they were around sixty bucks.

Striper, I believe the tubing on my 93 is half inch, not 5/8's. I don't know if the earlier trucks used larger tubing though. That said, I used 1/2 inch tubing for plumbing in my auxiliary cooler which has 1/2 tubes.

Tubing is measured O.D.

Hose is measured I.D.

Do not restrict your transmission fluid cooling capability, especially if you work the truck (pulling etc) or if you bomb the heck out it and drive her hard. You'll read all sorts of folks who don't think so if you search, common size cooler lines are 3/8 etc. Our cooler lines are 5/8 OD, Allison uses 3/4 FWIW. People don't want to pay more for rated temperature and pressure line, or no availability. Temps and pressure asside, the right sizing is the cheapest insurance to keep from having a large expense...

Your tubing is about .555 depending on the wall.

I have bought replacement steel tubing in .527 or .555 Inside Diameter. Outside Diameter is 5/8 or .625, that is the factory steel transmission cooler tubing size. The thicker wall has a higher pressure rating, either wall size is overkill...

After doing major automatic transmission plumbing work on 2- 1993 1st gens, anywhere from aux tranny coolers w/ fans and t-stats, all the way to an atf valved flush system on both trucks, I know for sure it is 1/2" ID for transmission hose, and use 1/2" for any hard tubing and all fitings are 1/2" NPT, including compression fittings.

And my old 1st gen also had a tranny cooler located underneath the Bed on the driver's side, right in front of the fenderwell. So they could actually have 3 tranny coolers. Upfront, under turbo, under back bed.