Can extra trans cooler affect shift quality?

[davepl]

I was wondering - if, like me, you plumbed your automatic trans through the factory radiator cooler and an auxiliary cooler, I've heard that doing so can increase the pressures in the transmission.

Does anyone know (a) if that's true, and (b) whether it can change shift feel as a result?

I have a 4L80E in my truck plumbed that way and wonder, as it's supposed to be a completely stock rebuild but it shifts 1->2 very crisp if you have any RPM going at all.

[Hart_Rod]

Originally Posted by davepl

I was wondering - if, like me, you plumbed your automatic trans through the factory radiator cooler and an auxiliary cooler, I've heard that doing so can increase the pressures in the transmission.

Does anyone know (a) if that's true, and (b) whether it can change shift feel as a result?

I have a 4L80E in my truck plumbed that way and wonder, as it's supposed to be a completely stock rebuild but it shifts 1->2 very crisp if you have any RPM going at all.

I've plumbed the last two I have built that way and haven't had any problems.

[ptc]

It will only change it if you dont top off the fluid to fill that extra space you have added into the circuit.

['68 Newtricks]

The fluid going to the coolers is at the end of the loop. The trans uses it for lubrication, cooling, and pressure before it's sent out. After the cooler it dumps into the pan. I also believe not all the fluid going through the trans ends up in the cooler. For some reason I think the pressure bypass is what sends fluid to the cooler, meaning there is more pressure going through the cooler in neutral/park than there is when driving. Like FMVB autos have less going through the cooler.

just thinking out loud

[mike16]

wouldn't it be unnessessarry to both eat and cool the tranny fluid. external tranny coolers cool the fluid more than the internal ones do. the internal ones rais or lower the fluid based on the temp relationship between the tranny fluid temperature and the coolant fluid temp.

some other disadvantage of the internal cooler is that if there is a failure water does not enter the tranny cooling system. disassembly of the radiator tranny lines can be a pain.

[57taskforce]

Originally Posted by davepl

I was wondering - if, like me, you plumbed your automatic trans through the factory radiator cooler and an auxiliary cooler, I've heard that doing so can increase the pressures in the transmission.

Does anyone know (a) if that's true, and (b) whether it can change shift feel as a result?

I have a 4L80E in my truck plumbed that way and wonder, as it's supposed to be a completely stock rebuild but it shifts 1->2 very crisp if you have any RPM going at all.

My 3100 is Plummed like this and I've had no problems either.

[davepl]

Originally Posted by mike16

wouldn't it be unnessessarry to both eat and cool the tranny fluid. external tranny coolers cool the fluid more than the internal ones do. the internal ones rais or lower the fluid based on the temp relationship between the tranny fluid temperature and the coolant fluid temp.

some other disadvantage of the internal cooler is that if there is a failure water does not enter the tranny cooling system. disassembly of the radiator tranny lines can be a pain.

I both heat and cool in some cases because I'm trying "stabilize in the middle". So I run through the air-to-air first and then to the air-to-water because I want the trans temp brought up to engine coolant temp.

I think some vehicles, like the Z06 with it's rear mounted trans, don't interface with the engine coolant at all, so it's probably not a big deal, just the way I've always done it based on a hunch!

['68 Newtricks]

depends on your climate, the coolant just helps the trans warm up faster
also, the trans fluid is going to run hotter than your engine coolant no mater what, so the coolant will always help cool the fluid


EX: take a piece of steel. Get it red hot. Wave it around in the air for 20 seconds and measure the temp. Now heat it again and plunge it into some water for 5 seconds. Which cools the steel better?

Being in CA, I run the internal first and the external second. My external has a fan also. It's just there to cool the fluid more than if it was the internal alone.

[AnotherWs6]

I was always a believer in the factory and then auxiliary cooler plumbing route. Now I have a $2,500 transmission waiting to replace the blown one in my Silverado. Having talked to the guys that build such things, I am now 100% convinced not to ever use the factory cooler again.

My grandfather was big on towing and always added a cooler after the factory route to his tow vehickes. My grandfather never built 1,000HP capable race transmissions. I'll stick with the words of the guys that do.

That doesn't answer your question though. My guess would be that something done by your re-builder is causing this. Shift firmness is either mechanical or "tuned". Have you taken it back to the re-builder with your concern?

['68 Newtricks]

Running only an external cooler on my K5's 700r4 caused it to run hotter than running both. No other changes were made. Same synthetic fluid, same everything. Not saying trans builders don't know a thing or two, but I've already tested the idea on the Rubicon and Moab.

1-2 shift is the accumulator spring and valve IIRC
Any change in that over stock is going to run different. If the servo is different, it might shift different too. These are two things (vette servo/spring) I always change in all my transmissions (700r4 and 4L65) Might be why it shifts different, dunno

[67ChevyRedneck]

4L80e's are electronic... I'd assume you have a stand alone harness for it, can you make shift adjustments by plugging it in to a laptop?

[AnotherWs6]

Originally Posted by '68 Newtricks

Running only an external cooler on my K5's 700r4 caused it to run hotter than running both. No other changes were made. Same synthetic fluid, same everything. Not saying trans builders don't know a thing or two, but I've already tested the idea on the Rubicon and Moab.

1-2 shift is the accumulator spring and valve IIRC
Any change in that over stock is going to run different. If the servo is different, it might shift different too. These are two things (vette servo/spring) I always change in all my transmissions (700r4 and 4L65) Might be why it shifts different, dunno

^^^I don't doubt it in a situation like that. Drag racing and road racing, even off road racing, will cause good air to flow across the cooler. As will cruising down the road in a truck/tow vehicle. 4mph with a converter slipping over and over again.......... THAT is a torture test. Though not one a big cooler with an auxiliary electric fan probably couldn't handle.