Big block 727 3k stall Transmission overheats

[Mrs. 69 Bird]

I am having a over heating issue with my big block 727 Transmission with 3k stall converter, I have a trans cooler with a fan pushing through it but after maybe 15-20 miles of driving, it would get upto 210 degrees, I evened bypassed the thermostat to straight 12 ignition switch for the fan but will still overheat over time.. Any ideas on how fix it?? Or should I

switch to a Tremek 6 speed manual transmission? Any information will be a helpful..

 

[bm02tj]

At a slow cruise gear down so converter is not slipping that is where the heat comes from
After trial and error you will find what gear to select

 

[pnora]

What radiator? Do you have a shroud? What type of fan? What is your ignition timing?

 

[ruffcut]

Lots of unknown variables like @pnora was asking.

 

[pnora]

One item jumped out at me on your engine picture. Pulley size. That crank pulley is small and the water pump is large. That tells me you may not be spinning the water pump fast enough.

 

[A70Runner]

I may be wrong but I think they are talking about the trans overheating, not the engine .

 

[F4R/T]

Your combo sounds off, what gear ratio are running because you need to get the engine out of the stall range of the convertor . Pulley size is critical and fan size and set up, radiator . Share some more information on your combo.. cam compression etc.

 

[1 Wild R/T]

As others have mentioned... Please clarify, engine temp or trans temp... My take is your concerned about trans temp... So gear ratio becomes a serious question... A 3K stall convertor, especially one of the budget minded variety needs to live at of above it's rated stall... So if your running 3.23's and what looks like a pretty tall tire at 65 MPH your spinning the engine at around 2500 RPM's and the convertor is slipping creating heat... You either need to drive faster, change to a numerically higher gear or run a shorter tire.. Or swap convertors... Either a lower stall, or a tight 3K unit...

Assuming a 28.5" tire & 3.23 gears 80 MPH is 3000 RPM's...

 

[#41]

Not too many people run a trans temp gauge. IMO, it does not need fixing. 210 is not excessive for a 727 with a 3000 stall in a warm climate.

 

[sabre67]

 

[493 Mike]

210* is not even hot enough to boil water. Just like engine oil, transmission oil has to boil off any moisture from condensation.
Mike

Mechanic Base
https://mechanicbase.com/transmission/normal...

What Transmission Temperature Is Considered Normal?​

Most modern automatic transmissions are meant to operate at temperatures between 175 and 225 degrees Fahrenheit. If it gets any hotter than this, there’s a mechanical problem that should be dealt with.

 

[DanielSlocum]

Headers? If so, are your trans coolant lines insulated from header heat?

 

[1 Wild R/T]

210* is not even hot enough to boil water. Just like engine oil, transmission oil has to boil off any moisture from condensation.
Mike
View attachment 1685844
Mechanic Base
https://mechanicbase.com/transmission/normal...

What Transmission Temperature Is Considered Normal?​

Most modern automatic transmissions are meant to operate at temperatures between 175 and 225 degrees Fahrenheit. If it gets any hotter than this, there’s a mechanical problem that should be dealt with.

I agree to a point.... 225 may be normal for newer vehicles running synthetic fluid but conventional fluid like most of our cars run starts breaking down around 200 degrees... I wouldn't be to concerned about 210 but if the temp continues to climb then it does become a serious concern... Luckily Florida doesn't have much in the way of mountains and I doubt that Roadrunner is gonna be towing any trailers...

 

[493 Mike]

I agree to a point.... 225 may be normal for newer vehicles running synthetic fluid but conventional fluid like most of our cars run starts breaking down around 200 degrees... I wouldn't be to concerned about 210 but if the temp continues to climb then it does become a serious concern... Luckily Florida doesn't have much in the way of mountains and I doubt that Roadrunner is gonna be towing any trailers...

I have switched to ATF+4 in all my TFs. After reading comparison specs I see no reason to use Dexron.
Mike

 

[Phantomx]

Agree with some above. If you’re cruising around with the rpm below the stall speed of the converter, it’s going to be making big heat because the converter is slipping like mad. It’s not a modern unit with converter lockup, so you need your cruise rpm to be above the stall rpm to keep it happy. You either need a tighter or more efficient converter, a smaller cam so you can use said tighter converter, or lower gears to make your cruise rpm higher (or just drive around in second gear). Or my personal favorite way of curing the suto trans blues, install a manual.
Travis..

 

[ruffcut]

Yea, I thought a tighter unit also would cure the overheating.

 

[Mrs. 69 Bird]

As others have mentioned... Please clarify, engine temp or trans temp... My take is your concerned about trans temp... So gear ratio becomes a serious question... A 3K stall convertor, especially one of the budget minded variety needs to live at of above it's rated stall... So if your running 3.23's and what looks like a pretty tall tire at 65 MPH your spinning the engine at around 2500 RPM's and the convertor is slipping creating heat... You either need to drive faster, change to a numerically higher gear or run a shorter tire.. Or swap convertors... Either a lower stall, or a tight 3K unit...

Assuming a 28.5" tire & 3.23 gears 80 MPH is 3000 RPM's...

Hello, sorry just getting back to the thread but yes, either a tight 3k stall converter or switch trans out.. As the others asked wether trans of engine, its transmission, engine runs cool.. The engine is a 440/512 440 source 650hp performance online engine build spec. Engine runs strong only 428 miles on a new build. Tranny builds heat even at 3k rpm above, I tried it several times, it still will heat up over time, dont know what is causing it.. the converter is a 9.5 inch high performance converter from a racing company in Tampa Florida, with a CRT Racing Valve body..

 

[1 Wild R/T]

Well... As you probably know, the 3K rating of a torque convertor is based on a number of variables.. Torque & horsepower being part of it.. If the convertor was rated at 3K stall with 400 HP & you have 650 in front of it the stall will be higher... Add to that the gear ratio of the axle... A 4.10 gear accelerates quickly reducing the load on the convertor so the convertor stalls lower, a 3.23 forces the convertor to stall higher... Throwing 3.55 or 3.73 gears in might help... Or get rid of the convertor & swap in a TKX 5 spd manual... Convertor can't get hot sitting on a shelf...

 

[Phantomx]

Or, if you have 3.23 gears, you could run an a833 4 speed and not require a gear swap as well
Travis..

 

[pnora]

One other thought is where is the sending unit? If its in the line you will see a higher reading and that might not be so bad. If its in the pan then it is getting a little on the warm side. Are you also using the factory style cooler in the radiator? If so I have seen the transmission temperature will eventually equal the engines water temperature. This is mostly at idle, traffic, and low speed driving. It takes a big auxiliary cooler to bring the temperature down and lot of road speed driving to push enough air through to make the cooler effective. The higher the ambient temperature the harder it will be to cool the transmission. If using the radiators cooler you could bypass it and just run off the auxiliary cooler and see what it does.