Torque converter 727

[Mr Cuda]

The 727 is an old design.  As features were added,  compromises were made.
First,  the lockup or A999 with no od. Yes, the lockup lowered heat through lack of converter flash, but only to a point. The rotating mass built some heat but likely airflow over the pan kept it down. Then as soon as you hit town,  the converter unlocked and resumed cooling.  We're talking the 80's with final drive being under 3.21.
Add overdrive in new cars  with 3.73 and going 80, and you start seeing burned up OD units.  I know mine did.
Chrysler really had a problem with a 727 variant behind the diesel.
Transgo has a mod that bleeds fluid to the cooler while in lockup.
By 1999, the new trans came out that had all the required features for modern technology.
Fluid flow from the manual

[Katfish]

So you're saying when the LU solenoid is activated , all fluid is diverted and doesn't flow to the cooler?
I'm driving on the Hwy for hours and the transmission lines are bone dry and the external cooler does nothing?

[Mr Cuda]

As with all hydraulic systems,  there is some fluid leakage internally,  but essentially yes. No cooler operation.
The converter is still getting a fill volume of fluid, but thats a metered volume.  I think its controlled but the valve shown in the picture. Once in high gear it's not much.
That's why we are all excited that chargerdon can do a couple heat tests with  his is switchable system.

[chargerdon]

Will do first chance i get. My A518 came out of a 1992 Dodge Van. On that model A518 its basically a 727 front and it shifts from first-second-third the same as any 727. The shift to overdrive 4th and Locking Torque converter is via two solenoids in the valve body and in the 92 Van it had a small computer to read speed and load and did the electronics.

Of course on a 74 Chally there is nothing like that so you can either hook up toggle switches to a 3 wire port on the transmission (one ground, and one post to provide pos voltage for the shift and another to control the torque converter. Many guys have hooked up pressure sensors to the diagnostic tranny fluid port to operate the shift to overdrive automatically and then a time delay for the lock up converter. Me i just use toggle switches for each. I found that i can leave the solenoid switch on for the 4th gear and it will operate just fine, shifting one-two-three-four with the shift to fourth fairly quick after the shift to third.. However you cant do that with the lockup converter or when you come to a stop it will shudder and possible damage the converter. I enjoy operating the switches...kinda like many enjoy stick shifts.

[SilverFrost73]

Recommend you call John at Cope Racing Transmission. I got the PTC torque converter and 727 trans from him a few years ago. Car runs great. But mine is a SB stroker to 416. It was dynoed at 528 ft-lb. The PTC I have is 11" 2800 stall. I am running 3.23 rear, 275/40/17, about 3000 RPM at 70 mph. I run a decent size trans cooler in front of the radiator and bypassed the radiator. Not a problem in CA.

I just looked at his website and he is no longer building complete transmission. But it does not hurt to call or email him with your questions. He was very helpful when I deal with him.

Thank you for the recommendation, I'll give him a call to see what he recommends for my application.

[SilverFrost73]

So I submitted a request into ACC Performance and they emailed me back suggesting the following converter.
I'm thinking this high of a stall is going to cause heat issues on long Hwy drives even with a aftermarket cooler. Am I wrong in thinking this?

[chargerdon]

Tried posting earlier.

Ok, today was 84 in Raleigh, took the Chally out for a drive until fully warmed up, then on a 7 mile trip around my area.   First was with OD and LU both on.   Speeds between 40-65 and when i got home, left engine running and transmission in neutral, and shot my tranny pan.   It read about 180  (several places says normal operating temps between 170-220 so i was right in the middle.    Repeated the trip with the LU off and read the pan and it was now 195 so about 15 degrees higher tho still in the normal range.   To verify repeated the trip with LU on and it still read about 183. 

So, conclusion is that the temp definitely is hotter without LU on but not drastically and still in normal range.    Incidentally, i performed my stall speed test again, by holding brake auto in gear, and brought RPMs up till rear tires began to spin, and my indicated RPM was 1900.   Not a drag racing stall by no means, but, more than enough as i have only 3.23 gears with 235x60x14 tires.   I can do burnouts with ease and in fact cannot take off by flooring it or it will go up in smoke.   Minimum speed before flooring is about 15 MPH and even then depending on whether on concrete or blacktop.  This is with a 408 stroker and Lunati Vodoo 703 cam.   So why would i want higher stall speed ?   

[Mr Cuda]

Very interesting  and thanks. Maybe the results would have changed if you did  the lockup off first?
Bigger question,  od on or off?

[Katfish]

Sounds right to me, I've always read you want LU to lower temps.
I don't see how you'd stop the pump from circulating fluid only during LU, doesn't make sense.

[chargerdon]

Very interesting  and thanks. Maybe the results would have changed if you did  the lockup off first?
Bigger question,  od on or off?

OD was on over 40mph in both cases.   I was going to repeat the test again with both OD and LU off and see what happens.   I would think the temps will be slightly lower than OD on and LU off as the OD on certainly puts a larger strain on the transmission than with OD off.   But, ran out of time.   Actually, i did the OD on and LU on as the first test, but, only read 150 at the pan, then when i did the OD on LU off and the temp jumped to over 190 i couldn't believe the difference so reran the OD on LU on and got the 183 temp.   Apparently, it simply took more than 7 miles to get it to normal temps.

The important thing to me is that with the 3.23 gears and 14" rims, cruising at 50 with OD and LU both on the RPM's (1500 is several hundred rpm lower than the actual stall speed of 1900 speed and yet the temperature stayed below 200 which is plenty safe and this is with using just the radiators cooling and not an auxiliary transmission cooler.   

[Mr Cuda]

I really appreciate you wasting gas driving around for us.
Temps will be the highest with od on and lockup off.
In that scenario,  you could be driving at engine speeds lower than the converter stall.
That will build heat fast.
1900 rpm stal speedl needs to run at 2200 to be safely out of flash.
On a side note,  what LIGHT THROTTLE engine speed does your 408 feel like its most comfortable?

[chargerdon]

It loves cruising at 45-50 and RPMs around 1600..   effortless...   It is the most responsive engine ive ever driven off the line...just give it half throttle and enjoy the ride.   

A few months back i used an application called Track Addict on my cell phone mounted on the dash.  Found a fairly flat and dead straight wide road...from dead stop toed into it about 1/2 throttle then nailed it at 15 MPH.   What a rush...0-87 in the 1/8 mile in 8.6 seconds.   Track Addict said 0-60 was 4.9 seconds.   Not bad for a street car with only 235x60x14 all season tires and only a 3.23 rear axle.   And yes when i nailed it at 60 it still burned some rubber...Sound was awesome...Flowmaster 40's really sound awesome.    So lucky no cops around...im 75 still acting like a 16 year old.   Now i know the new hot electric cars can do 0-60 in under 4 secs...but...no way they give the same feeling as that big engine and the sound it makes.