Lower Stall Converter

[Buddy's Ram]

I have a built transmission with a lower stall converter. Very firm shifts, but works great. When sitting at traffic lights the Transmission temperature climbs and the EGT is about 550 degrees if I leave it in drive. If I shift to neutral at the lights the EGT drops to about 350 and the transmission temperature will actually cool down. The idle speed stays at 750 in either case. Question: Can you lower the idle speed and would it be beneficial?

Thanks!

 

[AEdelheit]

you cannot change the idle speed on these engines and there really wouldnt be a benefit, for that matter the engine will fuel iteself to maintain that 750 idle rpm if need be, In neutral there is no load on the engine other then the drive belt accessories and the ATF is being routed through the cooler so it should be quite a bit cooler, how hot does your transmission get? In traffic mine will go to 180 if im annoyed in stop and go.

 

[Buddy's Ram]

Transmission temperature runs 160-170 in drive. The fact that the EGT is higher makes me think I am burning more fuel to keep the engine RPM at 750 under load. If we can't change the idle RPM then I guess I can just keep shifting to neutral at long lights.

 

[AEdelheit]

ya well downside of a tighter converter, more friction being created and force to overcome, but or actually driving its a good route, could look into an additional cooler, good luck though!

 

[LRutigliano]

I have a built transmission with a lower stall converter. Very firm shifts, but works great. When sitting at traffic lights the Transmission temperature climbs and the EGT is about 550 degrees if I leave it in drive. If I shift to neutral at the lights the EGT drops to about 350 and the transmission temperature will actually cool down. The idle speed stays at 750 in either case. Question: Can you lower the idle speed and would it be beneficial?



Thanks!

Mine performs very similarly. In Drive (idle) and foot on the brake, the EGTs are approx 450F and the trans temp will warm up fairly quickly.



Stock stall was approx 2200-2300 rpm.



New Dunrite triple disk stall is approx 1600-1700 rpm.



However, it feels like a new better truck pulling away from a stoplight...

 

[TCDiesel]

The more efficient the the TC the more heat it generates. . couple that with the more drag at idle ,Increased load on engine lower stall will increase trans temps considerably. When towing with lower stalls will create 250+ trans temps in stop and go traffic in short order. The only way to over come the heat generated is serious Pump upgrade with fan over ride switch.

 

[fox]

The more efficient the the TC the more heat it generates. . couple that with the more drag at idle ,Increased load on engine lower stall will increase trans temps considerably. When towing with lower stalls will create 250+ trans temps in stop and go traffic in short order. The only way to over come the heat generated is serious Pump upgrade with fan over ride switch.

That doesn't make sense!!!



The load/vs slippage creates heat.

The lower stall, tighter converters will run cooler before lock up once rolling.

If the OP is feelling it is too tight, ask them to loosen it up.

 

[NIsaacs]

I think TC was only talking about stopped and in gear.



Nick

 

[TCDiesel]

That doesn't make sense!!!



The load/vs slippage creates heat.

The lower stall, tighter converters will run cooler before lock up once rolling.

If the OP is feelling it is too tight, ask them to loosen it up.

It does. . if in fluid coupling only... None the less. Simply stated lower stalls *** in stop and go traffic.

 

[cerberusiam]

Transmission temperature runs 160-170 in drive. The fact that the EGT is higher makes me think I am burning more fuel to keep the engine RPM at 750 under load.

The trans temps are not an issue, they are well within the norm. Even the EGT's is not out of line with the load on the engine, that is pretty typical for an emissions engine.



The extra amount of fuel burned at a stop is more than offset by the better power transfer at other times.



Shifting to neutral for long stops is an easy solution if one decides it is worth it.

 

[MChrist]

My EGTs in drive, stopped are 400-450. In neutral, EGTs are about 250. Low stall Goerend trans~1700 stall

 

[SDrake]

I put a low stall on my 94 and drivability was tremendously improved except for this one issue, heat at idle but at least the engine idle was allowed to slow from its normal 750 or so to 500 rpm, a bit slow. I lived with it by watching temps and shifting into neutral at stops but when you shift back into drive you get a pretty good thump. Got me to wondering on my 03 with the idle that gets what ever fuel it needs to maintain 750 --- just how much worse this problem can get?



I would be OK with this harder thumping if I could learn if the band that takes the hit when you drop into drive has a service life not appreciably shortened by the unplanned (by the designers) increase in quantity and severity of cycles.



BTW FWIW -- My 94 original TC was a real dog, the low stall made a tremendouos improvement in response to the throttle off the line and in response to traffic in town. My 03 is not quite the dog but still needs improvement in my opinion. I miss that low stall feel in town.

 

[cerberusiam]

That doesn't make sense!!!



The load/vs slippage creates heat.

The lower stall, tighter converters will run cooler before lock up once rolling.

If the OP is feelling it is too tight, ask them to loosen it up.

It does and it doesn't. Too much depends on how the TC was setup. Lowering the flash stall won't increase efficiency as much and will generate more heat at an idle. Increasing the efficiency of the fluid coupling will lower the stall but will not create as much heat generated at an idle.



The heat is created by the amount shear forces geenrated in the fluid coupling not slippage, there is no slip in a fluid coupling only efficiency differences. A lower stall converter will over all run cooler because it spends less time churning the fluid and transfers the power better. Heat generation is more the tighter the coupling but spending less time accelerating actually lowers observed temps.

 

[Prairie Dog]

Make sure you slip it into neutral at longer stops.

 

[mrtrombley]

My Bully Dog gauge will read fuel flow as one of it's readouts. I ran it for a while using this readout. I noticed that when stopped at a light, if left in gear, the fuel flow guage read almost 3 times what it would read when in neutral. Probably not a big issue as far as real amount of fuel used, but I thought that was pretty interesting. So I most always put it in neutral when stopped in traffic.



I also learned in previous Defensive Driving courses that it is a good idea to be in neutral when stopped in case someone hits you from the rear. If in gear when hit, it is a natural reaction for your foot to slam the go pedal down to the floor. Guess what that does when in gear!!

 

[cerberusiam]

If in gear when hit, it is a natural reaction for your foot to slam the go pedal down to the floor. Guess what that does when in gear!!

I think your defensive driving instructor needed to do more driving before teaching, they were just a tad confused. :-laf



If your right foot is slamming down on the go pedal when stopped your already violating defensive driving habits. Right foot goes on the brake not the accelerator when stopped.



Fuel flow is purely a calculated value based on sensor inputs. It is about as accurate as the slip percenatges and engine load percentages. About the only conclusion that can be drawn is it is higher at an idle with a tighter converter but not 3x.

 

[Buddy's Ram]

Thanks for all the great input guys! I was really interested in the extra fuel, thus higher egt's when in drive. I track every tank and if I spend a lot of time in town it is noticeably lower. I was hoping we could lower the idle speed some. I love the way the truck drives with the tighter converter!

Buddy