Transmission Overheats 700R4

[Duke]

Help!!! I have a 1990 Chevy Sportside  4wheel drive truck. It has a 383CI, 370HP & 410 torque, 1-5/8 headers, 3:42 gear ratio, 31.5 tire diameter & a 700R4 with a deep pan. I can't find the reason the transmission is running hot & failing. Before the new engine was installed the trans. was sent to the local trans. shop for beefing up & a JW Performance lock-up converter 1900 stall was installed. The trans. failed after 3000 miles. Again they rebuilt it & all the lines were flushed.  I installed a temperature gauge in the truck with the pickup in the rear of the trans. pan, at the same time a Perma-Cool cooler with a fan was installed. The trans. was installed with another new converter & after 30 minutes of driving the temp. was at 240 degrees. They again went thru the trans. but with the same results. The TV cable & geometry was verified to be correct. The shop no longer new what to do so I received a refund. I purchased a Raptor Level 4 from  PATC with another new converter & it also ran hot & failed. Another of their trans. & converter was installed. It is also running hot but it was shut down as soon as the temp. went that high. The temp. was verified with a infrared gun, lines are clear, correct pressure at trans, 7 qts flow. We are at our wits in, no one seems to know what is going on but the entire trans. is hot. I have wondered if it could be the header heat but there is so many vehicles using headers that surely if that was the problem someone would know. If you could help me or point me to someone that could I would appreciate it.

[enjenjo]

What do you have for a cooler?

[HOTRODSRJ]

Is this just one tranny or many?  I can't understand some of your jargon. If it's one tranny, I would suggest a weak pump if all the other lines are clear.  Did your shop check for flow???  If not, then I would go there.  Also, synthetic tranny fluid will definitely lower op temps. Expensive tho...about $100 a fill.

[1FATGMC]

Where is the cooler?

Mine is in front of the radiator.  The fluid goes from the transmission to a large remote filter.  Then to the cooler built into a stock Camaro radiator and then to the B&M cooler in front of the radiator and back to the transmission.  It runs extremely cold, under 135 without pulling the teardrop and about 145-150 towing the teardrop.  Combined weight of the truck and trailer is 5800 lb..  Make sure your lines are not reversed, the "in" and "out" lines.  They are different than a 350/400.

I run headers and don't think that is your problem at all.

Is the converter locking up for sure in 4th?  If not that is probably your problem.  

I would also double check the TV hookup to the carb by using the information on my site.  Don't take someone else's word on that.  The hookup shouldn't effect the heat, but it has to be right or the transmission won't last.  Check it yourself.

c ya, Sum

[Crosley.In.AZ]

I would be curious of the operating main line pressure of the tranny, if lock up has been verified .  High main line pressure will develope lots of heat

As I read your OE post , the cooler flow and pressure was verified?  7 quarts per minute flow?

Cooler lines in and out will not make any difference. there should be no check valve in this cooler system of the 700r4 tranny

[slocrow]

So Duke, let me see if I got this correct. I'm guessing here but I suspect you installed the 383 at the same time as the first rebuilt 700R4. Is this right? What eng/trans combo did you replace? Anyway you've tried two rebuilds with one go through and two converters locally. The first going in 3000 miles (presumably from heat) and the second running hot almost immediately (30 min's). Doing a R&R with an inspection to the second and finding nothing internally wrong (that's the third) it was reinstalled and again over heated.
You received a refund, purchased a PATC and installed the forth (it failed from heat) and fifth tranny and converter. You stopped overheating the fifth and I assume it's still intact. Just wondering why you didn't stop when the forth was heating up? No big thing I guess.

Anyway that's 5 tranny's and 4 converters. As you did when questioning the header heat I'm also suggesting that after that many product failures it's not the product. I'd guess the cause is something else.

Was this the block that was originally in the truck? If not maybe this new block isn't square where the tranny mates. Also I like Sumner's suggestion that the converter may not be locking up in forth. I believe a bad ground would cause this and affect all the tranny's you've tried. Maybe the driver side plug-in which I'm guessing is common to all the boxes, got messed up.

Good luck but I'd start looking outside the transmission and converter for the problem. Let us know. Welcome aboard.....Frank

[1FATGMC]

Cooler lines in and out will not make any difference. there should be no check valve in this cooler system of the 700r4 tranny

Hi Tony I'm wondering about the lines not making a difference.  My fluid goes to the radiator and then to the aux. cooler.  I have a temp gauge on the transmission.  It always runs about 50 degrees cooler than the motor, so I'm thinking in the radiator the fluid might actually pickup heat, but dump it in the aux. cooler.

If the engine runs hot, say 200/210, and the lines are reversed couldn't the cooler fluid coming from the aux. cooler actually be heated in the radiator cooler?

One time I was going over Wolf Creek pass in Colorado with a bunch of guys and we weren't going slow.  I had the teardrop in tow and was running WOT in 3rd, and the converter was not locked up.  As I neared the top of the pass the motor temp and trans temp both went up.  The trans. temp rose to the motor temp of about 185 and then they rose in unison.  At the top they were both about 230.  Only at that temp for about 30 seconds and both temps dropped right away as I headed down the other side.  Once they got to the 185 of the thermostate the motor stayed at that and the transmission went on back down to 135.

I know there has been a lot of discussion about running the fluid through the aux. cooler first or the rad. first.  I think most people don't run a temp gauge on their transmission, so they never really know what is happening.  Me, I'll keep it the way it is.

BTW Duke sent me an e-mail first and I suggested he post here, so thanks Tony and the rest of you for giving him some things to think about.

c ya, Sum

700R4 Information

[HOTRODSRJ]

Cooler lines in and out will not make any difference. there should be no check valve in this cooler system of the 700r4 tranny

Hi Tony I'm wondering about the lines not making a difference.  My fluid goes to the radiator and then to the aux. cooler.  I have a temp gauge on the transmission.  It always runs about 50 degrees cooler than the motor, so I'm thinking in the radiator the fluid might actually pickup heat, but dump it in the aux. cooler.

If the engine runs hot, say 200/210, and the lines are reversed couldn't the cooler fluid coming from the aux. cooler actually be heated in the radiator cooler?

YOu make an excellent point here!

If you have a fairly large radiator and the shear capacity always overwhelms (keeps cool) any driving condition that you may run into, then running the tranny output thru the radiator appliance FIRST is okay.  The bottom of the radiators usually stay 30 to 80 degrees cooler than the engine temps, depending on ambient air temperature thru them.

But, if you are alway living on the "cooling edge" where you will see the engine temps commonly rise to over the thermostat opening/cycling point meaning incoming temperatures at the bottom of the radiator are high...then a complete external tranny cooler is necessary or you WILL pick up heat from the bottom of the radiator.

The example in the above post shows this very thing happening.

[Crosley.In.AZ]

Duke sent my a PM on this bbs.... some of his statements I had questions about , no answer from him yet.


Air to fluid coolers are less efficient.  fluid to fluid are the best ( I am told)

Chances are Sum , you are heating the radiator water in certain case, other times it is heating the tranny fluid.