• From: Fort Worth
  • Registered: 2011-07-19
  • Posts: 368

Topic: High Stall Converters

As drivers, we are basically low skilled.  We have always run an automatic trans in Speedy Monzales.  Early on, we put a 3000 rpm stall converter in it to save rotating mass.  We were always concerned about heat, but it was never an issue with the lowly 4.3 v6.  Transmissions were never an issue, even when we shifted manually ever corner to 3rd to 2nd to 3rd.

In Houston this year, we upped the engine game.  Never expected a transmission issue.  We had it apart, all was good.  Trans failed Sunday morning with loss of forward/reverse clutch pack.  Never detected any slipping during Saturday laps.

I am trying to decipher if the stall converter is the culprit through heat.  Historically, we exit corners in 2nd at 3500 rpms, shift at 5500 or so, dropping back to 3700 or so RPM for 3rd.  In Houston, we were not shifting to 2nd, so RPMs were dropping below 3000 on corner exit.  Am I correct in thinking the converter was "stalling" below the 3000 rpm mark and heating the fluid up?  Does it not slip past 3000 rpm?  If RPMs are above 3000 rpm, does the stall converter not generate more heat than say a stock 1800 RPM stall converter?

Organizer's Choice Award 2011 Heaps in Heart of Texas
IOE 2012 North Dallas Hooptie
2014 ECR Class C WIN;  2015 MSR Class B WIN
Speedy Monzales
  • Jimmy
  • Ripened Lemon
  • Online
  • From: Collegeville, Pa
  • Registered: 2019-06-19
  • Posts: 134

Re: High Stall Converters

I am no transmission expert but I do know that I smoked a brand new rebuilt chrysler 727 by down shifting it manually .

Once I left it in Drive the replacement tranny has made it 4 races with the 5th coming up at Pitt


As far as a 3000 rpm stall speed - I think your analysis might be right - the converter is slipping beow 3000 rpm which generates heat. But I would defer to people wiser that me ( just about everybody ) on that subject.

Good luck

Cordoba
  • chaase
  • Lemons Staff Stalker
  • Online
  • From: East Meadow, NY
  • Registered: 2009-08-06
  • Posts: 1,560

Re: High Stall Converters

You are probably correct that it is heat generation. Personally, I wouldn't run a high stall converter for Lemons. I would go as close to stock as possible. You want as little slip as possible.

1992 Saturn SL2 (retired) - Elmo's Revenge -  Class B winner, Heroic Fix winner x2
1969 Rover P6B 3500S(sold) - Super G-Rover - I.O.E Winner, Class C Winner
1996 Saturn SW2 - Elmo's Revenge (reborn!), Saturn SL1  Dazzleshipm Class C x2 and IOE winner
1974 AMC Javelin - Oscar's Trash heap - IOE,”Organizer's Choice" and "I got Screwed" award winner
  • From: Raleigh, NC
  • Registered: 2019-10-28
  • Posts: 93

Re: High Stall Converters

Really big piece of this puzzle is missing - I'm assuming you are not monitoring your transmission fluid temperature?  If you haven't already, definitely give some thought to adding that somewhere along the line, preferably leaving the transmission heading to the big ass cooler.

What transmission are we talking about?  700R4?  Assuming something with manual valve body control. Any chance something wasn't just exactly right when 'we had it all apart'?  Line pressure changed, filter didn't go in quite right, some shmutz got into the valve body, etc?  I know these are probably all unknowns, but, just pointing out (which you very well may already have considered) that it could be something completely unrelated to the torque converter. 

As for how torque converters work, I actually am not all that well versed on them, but, the logic *seems* sound, for what that's worth.  I've always been instructed that lower stall means lower heat generation.  Lower stall speed, higher line pressures, and big ol' cooler.  Fresh, clean fluid probably doesn't hurt.  Hopefully, your issue was a transmission overheating from a torque converter, just throwing some things out there to consider.

Semi-Sentient Centenarians
1996 Buick Century - we upgraded our crappy GM sedan with parts from a crappy GM minivan.
"It's got a van motor, a 220 cubic inch plant, it's got van tires, van suspension, van shocks. It's a model with the catalytic converters ripped out so
     it'll run good on regular gas. What do you say, is it a racecar or what?" - Blues Brothers, Probably
  • From: Fort Worth
  • Registered: 2011-07-19
  • Posts: 368

Re: High Stall Converters

mthew_m wrote:

Really big piece of this puzzle is missing - I'm assuming you are not monitoring your transmission fluid temperature?  If you haven't already, definitely give some thought to adding that somewhere along the line, preferably leaving the transmission heading to the big ass cooler.

What transmission are we talking about?  700R4?  Assuming something with manual valve body control. Any chance something wasn't just exactly right when 'we had it all apart'?  Line pressure changed, filter didn't go in quite right, some shmutz got into the valve body, etc?  I know these are probably all unknowns, but, just pointing out (which you very well may already have considered) that it could be something completely unrelated to the torque converter. 

As for how torque converters work, I actually am not all that well versed on them, but, the logic *seems* sound, for what that's worth.  I've always been instructed that lower stall means lower heat generation.  Lower stall speed, higher line pressures, and big ol' cooler.  Fresh, clean fluid probably doesn't hurt.  Hopefully, your issue was a transmission overheating from a torque converter, just throwing some things out there to consider.

TH350 rebuilt cheaply by me.  Not my first, but by no means an expert.  Trans had 6 full races and was functioning fine, but found metal in fluid.  Discovered a spun bushing.  Replaced fibers and seals and bushings as needed.  Never measured line pressure, but I have the gauge to do it. 

Stock valve body with shift kit.
Temperature...correct, no gauge.  Was already on the punch list.

Have not torn apart yet.  Plan is good rebuild kit, fan on cooler, gauge for temp, stock converter.

Organizer's Choice Award 2011 Heaps in Heart of Texas
IOE 2012 North Dallas Hooptie
2014 ECR Class C WIN;  2015 MSR Class B WIN
Speedy Monzales