jdrafke

Well, not compared to a civic but compared to my buddies 91 z it seems to be a bit slow. His is a stock 700r4 with a shift kit. Now dont get me wrong this isnt with reving up the converter just pushing the gas. From a light throttle to a medium throttle his seems to be better. Also, without reving the stall and just going wot his seems to be a little quicker. Could this be because of the 2.77 with the 2500 stall. I love to rev the converter up everytime but i just dont like to do that (not good for drivetrain). Is the stall slowing me down out of the hole being becuase i only have 2.77s? WOuld putting a new gear set and carrier(3.27-3.45) in the back make a big difference?

xpndbl3

iTrader: (5)

i'm sure some bigger gears would definately help a LOT out of the hole.

jdrafke

Yea def. U think it could be making my car even slower though with the stall. Im not talking when i rev it up just a mid throttle or 3/4 throttle launch. It sucks 9 bolts are so much money to build up:-(. I dont think my posi is working niether because last night i did a reved up burnout and left only one patch:-( Can i check and see if my posi is ompletely dead. It does whine a bit now and then.

Nixon1

I doubt the stall is slowing you down. Even though you're lightly modified, it's a 350 so it should have enough power/torque to pull a 2600 stall just fine. Just put some better gears on it. Those 2.77's are almost surely what's making you a dog out of the hole.

F-BIRD'88

Actually you're right. The stall is slowing you down.
If you're talking about acceleration at less than full throttle. Like pulling away from a light at say 1/3 to 1/2 throttle.

A High Stall converter is just that . It has a higher stall speed. It allows the engine rpm to flair up more before coupling occurs.
This allows quicker acceleration at full throttle by allowing the motor to move into is more powerfull rpm range at launch.
But the down side is the converter is less efficient at part throttle light loads. Like when you leave the start at less than full throttle.
This slipping or dyno effect is especially noticable on a stock diameter converter that has been modified internally to achieve a higher stall speed. (fin angle, clearance and stator window mods)
Esentually the coupling speed relative to load input is raised.
The design of a torque converter is a compromise of different driving characteristics.
A "high stall" torque converter trades off coupling efficientcy at low spped/input for a higher stall speed at full throttle.

Just push the throttle further to the floor.

Yes a higher rear gear ratio will help a lot.
With 2.77's your converter stays "on the stall" as you accelerate for too long. With say 3.73's the rpms would raise much faster during launch and pass through the coupling phase of the torque converters' operation.
The "dyno effect" will be much less noticable.

jdrafke

Hey thanks for the good info guys. Another question real fast is to whether the damn thing is slipping or not. When i give a full throttle launch with just full pedal the rpms rise to about 500 before it shifts but if i rev up the converter it goes way into the redline(about 5900 rpm). Is this because my trans is slipping? It shifts fine under light throttle and goes into overdrive fine. The tv cable is adjusted so that there is barely any line pressure(the cable isnt pulled out very far). If i pull the cable out farther it will make hte shift points higher right? I want them to be lower but it doesnt seem it can go any lower.

F-BIRD'88

Define "I rev up the converter".

jdrafke

basically i have the break to the floor rev up the rpms to about 1900 and when we go i let off and floor it. basically try and flash the converter

razor

https://www.thirdgen.org/newdesign/tech/detent.shtml

Make sure you have the detent cable set correctly. It sounds like you are killing your tranny by not having enough line pressure to create a firm shift. Do a search on the tranny board for this. It is critical that the cable be set as described and then left alone. You can do serious damage to the tranny otherwise.

F-BIRD'88

Mis-adjusting the TV cable to give less pressure will only change the shift point a little. But it will affect the trans
life a lot. Sounds like its flairing up during the shift.
First thing to do is to readjust the TV cable properly.
Full throttle should fully pull the cable.
You're risking damageing the transmission by misadjusting the cable. If you want to modify the shift points, play with the governor not the tv cable.
Don't know why this flairing up during the WOT shifts tends to happen more if you load up the converter during the launch.
As a note: the car should accelerate the best by stabbing the throttle from an idle.
(assuming you have good traction)

Fast305

So basically you'll are saying that a 2,600 rpm stall is a little high for daily driving efficiency. I can agree with this. Why do you think trucks use special converters. They are designed to efficiently move power at low engine speeds without heating up the trans. The 2,600 rpm stall works good @ WOT but suffers @ part throttle.

I would change the gears down to about 3.23 or 3.42. That will help you get out of the hole quicker. I have a friend with a suburban that bracket races it. He changed from 2.73 to 4.56s and dropped his quarter time by 2 seconds. Keep in mind suburbans have a much larger tire. His 4.56 are probably equivalent to 3.42s or so in a camaro. I know this because with a turbo 350c he is still only running @ 2,600 rpm @70 down the highway which is about right for his rig. Point is go to 3.42s and keep the stall or put the factory stall back in and keep the 2.73s.

AM Racer

I'm having a hard time understanding what you mean by revving up the converter?

A converter is a torque multiplier as long as you're away from the point of matching rpm ( converter input to output).

430T/A

I think what he means is pre-loading the converter with a little brake torque...

Ditch the 2.77s, swap in some lower gears, 3.73s or so. that outta help the anemic L98 get up and go...

AM Racer

A gear change will help some. You have a trade off to take into consideration with a street setup. With lower gears in the rear, the converter will go to a 1:1 ( theoretical) much sooner. This means that you lose the torque multiplication feature of the converter sooner. Converters only build power while in the "slipping mode". Afterwards, it's gear and motor only.
Never try to change the wide open throttle shift points with the TV cable. You'll cook the trans if you haven't already.

430T/A

A true 1:1 not possible, with out a lock up converter, not to nit picky... But a stall converter is only good for off the line, if the converter was slippin all the time, like it does in full throttle flogs, your tranny would last about 15 minutes. HE is right,once the converter stalls, and begins to catch up to the motor, your torque multiplication goes in the crapper, its up to the motor from there on out...

AM Racer

I only used 1:1 as an example since the best case of 3~7% slippage has no measurable multiplication.

MYBLUZ

Good info in this post guys, I just have one argument. jdrafke had said he doesnt like to load the converter because its hard on the drivetrain. But later said something about burning out. Burning out is far more hurtful of the drive train than loading the converter. IMO.

Nixon1

Worst thing you can do to the drivetrain by loading up the converter, I imagine, is breaking something on launch. And that's if you launch the holy hell out of it....I imagine you'd have to be doing at least 12's before you start breaking things, unless they were parts on their way out to begin with.

430T/A

you have to remember, Driveline parts in mustangs are far superior than those of f-bodys. Parts start breaking in low-13s. If I'm not mistaken, fox-bodys have 8.8" rear, compared to the 7 5/8". not to mention the driveshaft and u-joints are about the size of a pencil.... and the almighty 700r4, don't get me started on the slush box.........

AM Racer

You've got a lot less to break in an auto car than a manual tranny.
Just make sure that you've got more than enough of a cooler on the trans cause you're building lots of heat.

Fast305

A good cooler is a must with a 2000+ stall. I have a 1800 rpm stall in my tow vehicle. The transmission was running 240* all the time whenever I wasn't in lockup. Towing in 3rd near full throttle. I put a good cooler on it (the biggest I could find/fit, looked like an A/C condensor LOL) in series with the stock cooler. I ran the stock cooler after the aftermarket so that on cold days the transmission isn't too cool. Now it won't get above 180*, in fact it sits @ 180* no matter what.