Trying to identify an RPO code related to my transmission.

[zetros]

Hi guys. My '97 Express van has the GM RPO Code KD1 (COOLING, TRANS OIL) . This implies it has some sort of external transmission oil cooler to me, but from what I can tell the trans cooler lines seem to go directly to the engine radiator.

It appears to me that it's some sort of dual layer radiator that cools both the engine coolant and transmission oil. I'm under the impression this may very well be a G van quirk, but I do not know for sure.

My question is, is that an upgrade from what would otherwise be stock on a van of this vintage or is this the "base" cooling option? From what I can tell conventional GMT400s have a smaller trans rad in front of the main radiator, but that is not the case for me. That being said, I'm not very experienced with this generation of trucks so please correct me if that is not the case.

I'm considering fitting an external radiator if it is not the case to help out the 4L60e with cooling considering the weight of the conversion equipment too.

Is what I have sufficient or not? I'll have to go for a drive and monitor the transmission oil temperature using my OBDII reader.

Thanks

 

[red98]

Hi guys. My '97 Express van has the GM RPO Code KD1 (COOLING, TRANS OIL) . This implies it has some sort of external transmission oil cooler to me, but from what I can tell the trans cooler lines seem to go directly to the engine radiator.

It appears to me that it's some sort of dual layer radiator that cools both the engine coolant and transmission oil. I'm under the impression this may very well be a G van quirk, but I do not know for sure.

My question is, is that an upgrade from what would otherwise be stock on a van of this vintage or is this the "base" cooling option? From what I can tell conventional GMT400s have a smaller trans rad in front of the main radiator, but that is not the case for me. That being said, I'm not very experienced with this generation of trucks so please correct me if that is not the case.

I'm considering fitting an external radiator if it is not the case to help out the 4L60e with cooling considering the weight of the conversion equipment too.

Is what I have sufficient or not? I'll have to go for a drive and monitor the transmission oil temperature using my OBDII reader.

Thanks

Can't say for certain on the vans, but I can tell you my 98 K1500 5.7 Auto has a trans. cooler bracketed to the front of the radiator with some little metal straps, and it is definitely external.

I could see them doing an internal one on the vans for space reasons, though.

Just add another aftermarket one on top if you're worried about it, can't be that expensive, it'll increase the longevity of the trans. and I can't really think of any downsides other than cost.

 

[stutaeng]

Yeah, don't know what would be factory for your generation van. But here's a good read adding an external cooler:

https://chevroletforum.com/forum/ex...ons-2019-savanna-3500-6-0-gasser-97491/page2/

How much are you planning on towing?

 

[zetros]

Can't say for certain on the vans, but I can tell you my 98 K1500 5.7 Auto has a trans. cooler bracketed to the front of the radiator with some little metal straps, and it is definitely external.

I could see them doing an internal one on the vans for space reasons, though.

Just add another aftermarket one on top if you're worried about it, can't be that expensive, it'll increase the longevity of the trans. and I can't really think of any downsides other than cost.

I've had my front grille off and there definitely is no cooler bolted to the front of the engine rad. I may not be planning on towing much, but I want to make this van last and I'm fine with throwing some money into it to make it run even better for longer. Last thing I want to do is figure out how to rebuild a 4L60e or try to fit a 4L80e in this thing.

(That being said, it would be cool having a 4L80e in this)

 

[df2x4]

It appears to me that it's some sort of dual layer radiator that cools both the engine coolant and transmission oil. I'm under the impression this may very well be a G van quirk, but I do not know for sure.

The GMT400 trucks all have the in-radiator trans coolers like yours as well. Some of them got the smaller AUX cooler in front of the radiator in addition, but not all.

 

[zetros]

The GMT400 trucks all have the in-radiator trans coolers like yours as well. Some of them got the smaller AUX cooler in front of the radiator in addition, but not all.

Thanks for the confirmation. Unfortunately my OBDII scanner does not have a readout for the transmission oil temperature so I cannot monitor it before I shell out the money for a gauge. I'm sure I'll figure it out though.

Thanks.

 

[stutaeng]

Just add an trans. temperature guage.

There's a 1/8 npt plug that's used to pressure test them. Put your sensor in there and monitor.

 

[alpinecrick]

Hi guys. My '97 Express van has the GM RPO Code KD1 (COOLING, TRANS OIL) . This implies it has some sort of external transmission oil cooler to me, but from what I can tell the trans cooler lines seem to go directly to the engine radiator.

It appears to me that it's some sort of dual layer radiator that cools both the engine coolant and transmission oil. I'm under the impression this may very well be a G van quirk, but I do not know for sure.

My question is, is that an upgrade from what would otherwise be stock on a van of this vintage or is this the "base" cooling option? From what I can tell conventional GMT400s have a smaller trans rad in front of the main radiator, but that is not the case for me. That being said, I'm not very experienced with this generation of trucks so please correct me if that is not the case.

I'm considering fitting an external radiator if it is not the case to help out the 4L60e with cooling considering the weight of the conversion equipment too.

Is what I have sufficient or not? I'll have to go for a drive and monitor the transmission oil temperature using my OBDII reader.

Thanks

I have a 96 Express and 02 Savana, both have the KD1 RPO on the build sticker, neither have the external cooler.

In GM nomenclature:
AUXILARY cooler is the heat exchanger in the passenger side radiator tank.
EXTERNAL cooler is the cooler that is located out front of the radiator or condenser if equipped with AC.

I have 265k on one van, bought it with 155K on it, and replaced the trans 110k ago, the other van has 201k on it, I bought it at 60k and have never replaced the trans. The everyday payload on both vans are pretty much maxed out, plus I have a stack of ladders on top that act like a big sail. It's always bugged me that these vans didn't have the external cooler, and I have threatened to install a cooler (I have two GMT400 coolers sitting on my parts shelves).

BUT.......I keep my fluid BRIGHT RED--not red, not dark red, not brown, not black, but BRIGHT RED. I have come to believe keeping the fluid new in these 4L60's is at least as important as a big *** cooler out front. I installed a drain plug in the pans and pull the plug on them, top them off, every 2-3 engine oil changes.

There was a member on here who was having trans overheating problems when towing despite having a larger aftermarket cooler on his Suburban, only to find some previous owner has disconnected the auxiliary cooler.

Although towing may change the equation, it's pretty obvious from owning my overloaded vans for 15+ years that the auxiliary cooler works, and works well. Having said that, an external cooler will never hurt and may be extra insurance. Just keep the fluid bright red regardless.

 

[zetros]

I have a 96 Express and 02 Savana, both have the KD1 RPO on the build sticker, neither have the external cooler.

In GM nomenclature:
AUXILARY cooler is the heat exchanger in the passenger side radiator tank.
EXTERNAL cooler is the cooler that is located out front of the radiator or condenser if equipped with AC.

I have 260k on one van, bought it with 155K on it, and replaced the trans 110k ago, the other van has 201k on it, I bought it at 60k and have never replaced the trans. The everyday payload on both vans are pretty much maxed out, plus I have a stack of ladders on top that act like a big sail. It's always bugged me that these vans didn't have the external cooler, and I have threatened to install a cooler (I have two GMT400 coolers sitting on my parts shelves).

BUT.......I keep my fluid BRIGHT RED--not red, not dark red, not brown, not black, but BRIGHT RED. I have come to believe keeping the fluid new in these 4L60's is at least as important as a big *** cooler out front. I installed a drain plug in the pans and pull the plug on them, top them off, every 2-3 engine oil changes.

There was a member on here who was having trans overheating problems when towing despite having a larger aftermarket cooler on his Suburban, only to find some previous owner has disconnected the auxiliary cooler.

Although towing may change the equation, it's pretty obvious from owning my overloaded vans for 15+ years that the auxiliary cooler works, and works well. Having said that, an external cooler will never hurt and may be extra insurance. Just keep the fluid bright red regardless.

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.

 

[df2x4]

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, plus you keep the added benefit of bringing the trans fluid up to temperature faster in cold weather.

I added an AUX transmission cooler to my red truck when I did the 4L80E swap and set things up so that the fluid flows through the in-radiator cooler first, then the AUX cooler, then back to the transmission. I'm not actively monitoring trans temp in any way, but nothing has exploded or caught fire yet.