I've noticed lately that under normal driving, the trans temps are not even reaching 160 degrees on the colder days. As we know, high transmission temperature can cause instant death to an automatic trans.

But how low is too low? I've always aimed for 175-200 and with the trans cooler and I've never seen above 200, even on hot days. I've seen as low as 149 though under extended highway driving on colder nights.

So what are some opinions on minimum fluid temperature for proper fluid flow and transmission operation?

 

IMO, there is no min. fluid temp for best results. Granted, I've never run the car hard with trans temps under about 140/145, but that's mostly because I WILL NOT for any reason beat a cold motor. And by the time the motor/oil is up to temp, the trans is usually around 140+.

 

I like an operating temp of 160 - 180. I shut down at 200 and try not to do WOT blasts when the temps are cold.

 

yea 200 is where you have to start worrying...

 

I generally think of 160-190 as being ideal but 140-200 as being "ok". I have no real proof of this idea that I've formed, it's just that...

Number 1 rule? I absolutely WOULD NOT go WOT above ~220. That's just begging to kill frictions in a hurry, IMO. If you're seeing close to that then it's time to install better cooling.

 

I live in Southern California (warm cliamate), and have a B&M 24K cooler, with a 3 Qt. deeper pan, with a stock tranny & TC. On cool days on the freeway, I average anywhere between 135 and 150 degrees. In town I average 160 to 180 degrees.

SteveC

 

Isn't there something about the trans not going into
lockup until a certain temperature threshold? Is this
ECT, or TCT?

 

Carl Rossler told me that he likes to see between 135 and 165. He also said temps below 200 are fine.

He did say that below 135 the trans could flash, and once that happens it will only get worse. He told me to tune so that line pressures are:
50% at 25%TPS
75% at 50%TPS and
100% at or above 75%

SC-

 

I have burnt up the stock tranny, and 2 built ones. I just burnt up my 3rd this weekend. I too have a cooler, and a deep pan. I hate the 4L60E. It is a crap shoot and an expensive one to boot.

 

dragon, how much power are you making?

The 4L60-E actually impresses me for a street/strip tranny. It can be made to take 525 RWHP somewhat reliably and can take ~450-475 in a daily driven street car that gets pounded on relentlessly.

The biggest reason that some people have good luck while others have bad luck with the 4L60-E is the talent of the builders (NOT necessarily due to the parts that are installed.)

 

Exactly Colonel. I mentioned this the other day but I know know how many people actually noticed.

70% builder
20% parts
10% luck

I've seen "built" transmissions with all the bells and whistles fail behind a 400RWHP H/C setup and mostly stock rebuilds last behind F/I-nitrous 600RWHP setups. The difference was almost always who built it.

I think some of it also has to do with the driver. For example, a lot of highway-racing type 4-2 and 3-2 kickdowns behind a 400+hp motor can shorten the transmission life considerably. Boosted motors tend to make a lot of torque at low RPM, and a "built" trans won't last worth a damn if it's not tuned for more line pressure at low RPM. And so forth...

There is a big difference between a transmission "assembler" and a transmission "builder". Wich is also the reason most transmission shops, despite specializing in rebuilding transmissions, have a 30% or HIGHER come-back rate.

For every post I see like "I got 40,000 miles from my stock trans and since I went to XXXX brand "built" trans I've smoked three in 5,000 miles, the 4L60 is a peice of crap...." I can see the problem from a thousand miles away, and it's almost never the trans is what ultimately failed

 

this is a good thread...there was one like this a few months back. i still cant figure out why my 4l60e's temp wont stay under 190 in the summer with a deep pan and b&m 24k cooler. anyway...i think next year im going to add a second, smaller 16k cooler. anyone see any reason why that might not be a good idea?

 

I was informed that the temp limit was 266F. The PCM fault indicator will show on the dash & the trans will lock into 3rd when this happens (havent reached this point, but its what I was told by a trans builder).

 

Dean, that may be the "factory" temp limit, but for a hi performance application, 200 is MAX you want to ever see.

 

up ya go

 

Why only 200? If kevlar clutches/bands can handle high temps better than stock, I cant see why it shouldnt handle as well or better than the stock limit. I regularly see 210 on long hilly trips. It will usually come back down to 180 on a flat or downhill (large trans cooler fitted).

 

At 226 degrees the PCM will put the trans into "Limp Mode". Be there, done that 3 times.
Since installing the B&M 24K cooler and turning the fans on at 190 degrees, no more problems.

 

So who are some talented builders......I called around and was going to go with a Speed Inc. stage 2. I'm on the stock one with trans-go right now, but its slipping bad.

 

Odd, I have seen a 2002 LS1 car go as high as 242 degrees (as verified on a-tap) and not hit "limp home mode". Not that I would ever advise running the trans up to that temp...

 

Why only 200? Simple.

To protect the fluid.

Also, just because the clutches "can" handle more power, doesn't mean you should abuse them unnecissarely. The cooler they stay, the longer they will last. Heat is a tremendous killer for friction materials. Friction materials (clutches, brakes) work by converting kinetic energy to heat. The more heat they can dissipate and faster, the more efficiently they will operate. Think about a time when you really heated a set of brakes up, and they felt like total crap for a few minutes till they cooled. That tells us that as heat increases efficiency decreases, it's just as humans we need a drastic difference to be able to notice.

If you had a 12 bolt, would you do wheels up launches from every traffic light? Hell no. Just because a 12 bolt can handle a wheels up launch doesn't mean it's not BAD for it.