I was one who had probably 2 transmissions fail because of coolant infiltrating the internal radiators trans cooler. my rad did not leak and had no bad signs. the coolant didn't have any milky residue or anything and the tranny fluid had no signs of coolant in it. but I gernaded a tranny in 20 000 kms and it failed in multiple ways.
the problem was only found by a fluid anylsis while having the tranny rebuilt a stage 3 HD. since it's been 6-7 years and I do occasionally pull heavy loads for a couple hour trips I can say I have not had a single problem. also the company who suggested this since I couldn't afford a new rad said they do do this all the time without problems and it does not affect their warranty. every race truck has this bypassed is also what he said since this shop is a race shop first. so I almost see that oem rad configuration as an eventually timebomb that's guna eventually go off and I dont trust it. i mean it cost me 2 trannys!
so I personally wont ever trust that internal cooler again.
Al
The auxiliary cooler/heat exchanger also serves to warm up the trans on cold starts--important to keep line pressures and such down. Hydraulic fluid does get rather "stiff" in cold temps. If coolant is leaking into the trans the radiator is wore out--period. Time to get a new one. I'd rather have a new radiator than spend a lot of money on a stage 3 trans. Race shops are not somebody I look to for longevity of parts--been there.
GM didn't go to all the time and cost of developing and installing a heat exchanger in each side of the radiator tank because they thought it was superfluous. Their goal is to keep costs down so they can sell vehicles. As Shurkey has previously explained the heat exchangers use the "reverse flow" concept to heat/cool the oils, and that is the most efficient method to heat or cool a fluid. The coolant flows
down in the radiator tanks while the oils flow
up through the heat exchangers.
Guys buy a used truck that is new to them and often think of it as being "new" when it's not, and there are a lot of the systems on the truck one has to start looking at with a critical eye, especially beginning around the 150k mark (at least with normal maintenance). The heat exchangers in the radiators are not a weak link in these trucks. Naturally it can be damn frustrating when a heat exchanger leaks fluid into the trans/engine oils without it being noticeable and ruins the trans or motor.
Back in the day TH350's and 400's often didn't come with any kind of cooling for the trans--or engine oil cooling either. And those trans heat exchangers in the radiator may be the biggest reason 4L60E's last on average 50k longer in a pickup than the TH350's did. I know, I've owned one 71 K10 (bought in 73 with 22k on it) and three square body K10's with TH350's. I was grenading GM auto trans before most guys were on this planet. Through experience I've learned (most of) the things not to do to these trans, and hopefully most of the things that
should be done.
Although I do like the idea of having a fluid analysis done on the tans fluid. Where can a guy have that done at? Does Blackstone, Titan, etc, do trans fluid analysis?
When my 96 K1500 radiator sprung a leak at ~240K I bought the Spectre HD version when Advance had a 25% coupon and it was on sale. It was a drop in fit. Liked it so much I bought one for my 97 (which has 166k on it). Now you're motivating me to go out and install it as preventative maintenance............sheesh.
