Trying to identify an RPO code related to my transmission.

[alpinecrick]

Thank you for the clarification with the nomenclature.

I have just changed the fluid recently. It had not been changed since the van got a new 4l60e ~40k miles ago and while it was still red, it did smell a tad burny so I got it changed as soon as the new filter came in. Have driven about 200 miles or so since and still shifts firm and have no issues.

I'm still definitely considering slapping on an external cooler anyway. Would having it run in between the return line from the stock cooler and transmission work fine? Would still utilize the stock cooling power and the hypothetical secondary cooler.

Yes, that's how the factory does it. Into the auxiliary cooler in the radiator first, then out to the external cooler, then back to the trans.

And as df mentioned, the auxiliary cooler (which is really a heat exchanger rather than merely a cooler) heats the fluid when cold and brings the trans up to temp.

I mention the GM nomenclature thing because when folks start posting about the auxiliary vs the external coolers I have watched threads become one of those hysterical "Whose on first base" kind of threads.........

 

[df2x4]

I mention the GM nomenclature thing because when folks start posting about the auxiliary vs the external coolers I have watched threads become one of those hysterical "Whose on first base" kind of threads.........

I read your first post and then completely ignored the nomenclature part in my next one. I've just always referred to the external cooler as the AUX because it's supplementary, where as the radiator cooler is standard equipment. I never knew that GM referred to the in-rad cooler as the AUX.

 

[alpinecrick]

I read your first post and then completely ignored the nomenclature part in my next one. I've just always referred to the external cooler as the AUX because it's supplementary, where as the radiator cooler is standard equipment. I never knew that GM referred to the in-rad cooler as the AUX.

I have the schematic of the trans lines and cooler parts bookmarked somewhere that id's the parts by name, one of these days I'll run across it again........

 

[zetros]

Yes, that's how the factory does it. Into the auxiliary cooler in the radiator first, then out to the external cooler, then back to the trans.

And as df mentioned, the auxiliary cooler (which is really a heat exchanger rather than merely a cooler) heats the fluid when cold and brings the trans up to temp.

I mention the GM nomenclature thing because when folks start posting about the auxiliary vs the external coolers I have watched threads become one of those hysterical "Whose on first base" kind of threads.........

Hmm... Strange. I feel like that may have some unintended side effects if the transmission were to get real hot and inadvertently cause the engine to get hotter too, if the SBC runs cooler than the trans...

Maybe I'm being too worried, considering GM did this sort of setup from the factory. Would trying to bypass the stock setup completely and just have one big ol' trans fluid radiator be a fool's errand, or really just down to preference?

 

[alpinecrick]

Hmm... Strange. I feel like that may have some unintended side effects if the transmission were to get real hot and inadvertently cause the engine to get hotter too, if the SBC runs cooler than the trans...

Maybe I'm being too worried, considering GM did this sort of setup from the factory. Would trying to bypass the stock setup completely and just have one big ol' trans fluid radiator be a fool's errand, or really just down to preference?

I think the trans would die by the time it got hot enough to really effect the engine coolant enough to hurt the motor, and we would be shutting it down before that.

Having said that, my neighbor has a nicely restored '74 F-100 2wd with a rebuilt 390 (rebuilt Ford V-8's all seem to want to run warmish), with a rebuilt C-6, and one of those high dollar aluminum radiators. Engine coolant ran warmer than he liked. I gave him one of my GMT400 trans coolers to install and he says his engine coolant now runs 5-10 degrees cooler.

Given what I have read and seen, I would not give up the auxiliary cooler/heat exchanger under any circumstances exept maybe for a full house hot rod. Indeed, I would keep the auxiliary cooler and ditch the external cooler first.

As I mentioned my vans seem to do fine without the external cooler. Keeping the fluid bright red seems to do a lot for longer lived 4L60's.

 

[df2x4]

Would trying to bypass the stock setup completely and just have one big ol' trans fluid radiator be a fool's errand, or really just down to preference?

IMO it's down to preference. As I mentioned previously if you give up the cooler in the radiator then you give up heat transfer between fluids when the vehicle is warming up; but you also prevent the possibility of that cooler failing and allowing engine coolant to contaminate the trans fluid. I've never seen that failure personally but I know other members here have.

Personally I choose to keep the radiator coolers functional. I think they help out considerably.

 

[zetros]

I think the trans would die by the time it got hot enough to really effect the engine coolant enough to hurt the motor, and we would be shutting it down before that.

Having said that, my neighbor has a nicely restored '74 F-100 2wd with a rebuilt 390 (rebuilt Ford V-8's all seem to want to run warmish), with a rebuilt C-6, and one of those high dollar aluminum radiators. Engine coolant ran warmer than he liked. I gave him one of my GMT400 trans coolers to install and he says his engine coolant now runs 5-10 degrees cooler.

Given what I have read and seen, I would not give up the auxiliary cooler/heat exchanger under any circumstances exept maybe for a full house hot rod. Indeed, I would keep the auxiliary cooler and ditch the external cooler first.

As I mentioned my vans seem to do fine without the external cooler. Keeping the fluid bright red seems to do a lot for longer lived 4L60's.

IMO it's down to preference. As I mentioned previously if you give up the cooler in the radiator then you give up heat transfer between fluids when the vehicle is warming up; but you also prevent the possibility of that cooler failing and allowing engine coolant to contaminate the trans fluid. I've never seen that failure personally but I know other members here have.

Personally I choose to keep the radiator coolers functional. I think they help out considerably.

Thanks for the help fellas.

I think for now I'll get a transmission temperature gauge set up in this thing to monitor how hot it gets down here in the Georgia summer and then decide accordingly. I would have thought the thing would have a probe already, but unfortunately my OBDII scanner on my phone doesn't seem to have an option for transmission temperature. Darn.

I may still end up installing a radiator for the transmission fluid anyway, because if it gets hot enough when driving around with nothing on the hitch, I could imagine it'd easily overheat when towing. Cheap insurance, really.