A friend of mine just had his TH350 tranny rebuilt and had a 2500-2800 stall converter + a 2 stage shift kit installed. He got the car fired up and put it in gear (forward or reverse) and he can take his foot off the brake and the car don't move unless he puts his foot heavy on the gas it will launch the car.If he goes easy on the gas it doesn't budge. We both have no knowledge about stall converters and were wondering if this was the way it works. He is going to give the tranny place a call on Tuesday when they re-open but i figure i'd ask for some opinions here on his behalf.Thanks

David

That is exactly how a high stall-speed converter works.

As far as I've been able to determine, that's the way it works if your stall speed is too high. You really only need a high stall if your engine doesn't make any low end torque, like if you have a huge cam. Smaller engines often will use a higher stall speed as well. GM converters I've found can come with a stall as high as about 2100, and stock regular for the 1stgenv8 i think is about 14-1800.

This is a reprint from and old HPP article


http://www.boyleworks.com/ta400/psp/Twisting.html

With a high stall torque convertor, the trans should respond like a normal automatic, just with extra slippage and rpm to get rolling. It shouldn't require "heavy" throttle application to get something to happen.
From your description, it sounds like the trans is locked, then suddenly releases when you get to a certain throttle setting. Is this what's happening?

Thanks for the info and the link guys. He is running a 350SBC, he figures it to be around the 350-370hp range.Has DBL hump heads(done) and a large cam,headers.Car was originally a 6cyl and at current still has the original rear end in it.What is happening is like he needs to give it a good amount of gas for it to roll and when it does it squaks the tires. He basically doesn't like the feel or uncomfortable that the tranny is doing this.He has yet to take it out of the driveway for a run.Does it sound like he may have went a little overboard on the stall converter? Could it be like TOHcan mentioned, trans is locked? Or is this something he just needs to get used to? Thanks for the input.

David

so my only comment is pretty basic but thought i would metion it
double check the fluid level when the trans is warm and the engine idling, sounds lame but low trans fluid sucks, and makes trans do stupid things

I agree with the low fliud. I'm running the same 350 pretty modified with a th350 with 2500-2800 stall convertor and you don't have to apply heavy gas to it or break the tires. I did however experience this in a couple vehicles that leaked fluid and when they got especially low. Did they re-check after it ran awhile and filled up the convertor after install?

I wasn't meaning necessarily that the trans is locking up, just trying to clarify how it's behaving. Can you get more details, impressions, info, etc., on what's happening? Rpm, approx. throttle opening, is the car free to roll before the jerk (still could be locked but not likely), fluid level as mentioned, correct dipstick, make and type of shift kit installed, that sort of thing?
I had a switch-pitch set-up on my TH400 that allowed me to change the stall speed from about 1500 rpm to 2500 rpm at the flip of a switch, and the only difference was a bit higher rpm to get the car to move from a stop under normal driving, as well as the intended benefits of less load on the engine while idling in gear (041 cam) and the better launch when I got into it.

Only the first start from stop, or even after driving?

One of the current Chrysler torque converters (used in Durango and Ram pickups with 4.7 and 5.9) does the same thing after a cold start. It sometimes takes 2500 rpm to pull the dang thing out of the garage. After the converter fills and the trans pressure is up, it's all fine. In this case, it's poor design for a consumer vehicle. Dealers say it's "normal". I don't agree.

I am going across the street right now and confirm everything.He just dropped the motor and tranny into the car and has yet to drive it around the block, basically testing it out in his driveway.I suggested he drive the car a bit to truly get an understanding of it first before making assumptions.I post back shortly and thanks for the input all!

David

Well we took her for a test run through the neighbourhod.Car is idling about 750rpm. We took it over 2000rpm and it just lags all the way through .Motor sounds great and it seems like it just chomping at the bit to get the power to the rear wheels but seems like the tranny is holding it up somehow.We both were very unimpressed .Off hand he is not sure of the brand of shift kit or converter.He said he told them what his intentions were.

David

Did the converter FULLY seat into the trans when installing? Two clunks?

How is it acting otherwise? Shifting properly and firmly, etc.? Was the take-up smooth? What's the rpm with a more aggressive leave? As mentioned earlier, the converter allows more slippage when transfering the torque, so it may seem as if you're not getting the performance that the rpm and throttle opening used to give. It'll feel and sound as if you're slipping the clutch.
I opted for the switch-pitch because I wanted the low stall speed for 90% of my driving and the high stall to fill in the bottom end when I felt like having fun. If the engine is content to idle at 750 rpm, he may have too much converter depending on the rear gear.
I enjoyed the high stall speed off the line when at the stoplight Grand Prix because it sounded like I was trying much harder than I actually was, and made for a bigger surprise when I did use the Force.

It seems content idling at 750rpm. With the shift kit installed i didn't even notice it (as a passenger) shift into second unless he told me it did.He did not want to take it into the higher rpm ranges before he talks to the tranny shop.Had another friend with a shift kit in his monte carlo and it was a night and day difference before and after.Shifted hard and ripped the tires in second.This was dismal at best.Rear gearing we are not sure. It's an 80'malibu original 6cyl car with original rear.Not sure if he fully seated the converter but will ask.
Thanks,

David

CHECK THE FLUID LEVEL!!!!!

Checked and rechecked and fluid level is fine.

David

Sounds to me like a typical stall converter in the 2.5k range, working properly. If you want full blown drag race, it's a good way to go because that all the car is good for. One reason that it's hard to tell that it has a shift kit could be the relation between the engine rpm at the time of shift. Unless you're into it fairly good, the engine will probally shift well below 2.5k.

I don't have a tach, but a good guess for shift speed is 2k--tops, unless I'm into it some. If you have a 2.5k stall in the mix, it gives slush box a new definition. It's probally working fine. If the car has a stall, and he wants to verify whether or not it's correct, he needs to go out and matt it out. That's what's it's designed for and nothing else. Personally, I wouldn't own a stall converter.

Did you check to see if the car rolls freely? The emergency brake cables may have been moved, and may be causing the rear brakes to be partially applied.

Car rolls very freely.But he mentioned it feels like he is driving it with the parking brake on! (its not )He's on afternoons now so i won't see him till tomorrow and i'll find out what the tranny shop has told/suggested to him.
Car now has a 350sbc with big cam, 650 dbl pump holley,edl intake,new valves,rings,etc... TH350 tranny rebuilt with stage2 shift kit. Original 6cyl rear.
Car had 305 chev with hotter cam,650dbl pmp,edl intake,new valves, regular TH350 tranny and original 6cyl rear end.With this combo the car would launch well/rip the tires but had lacked the power he was looking for,hence the 350 and additional upgrades but it... Could we be possibly be looking at a rear end issue?

David

Unlikely, I would think you'd hear a lot of noise, and the car rolls easily. Any hint of a burnt smell from the tranny fluid?
I had the same diff in a '78 Malibu wagon, and it survived a couple dozen passes in the mid 14's, but I did end up breaking the side gears. Wouldn't hurt to start looking for a replacement now.

the high stall will probably negate any effects of a shift kit, but you should still be able to tell that it's shifting. From the description(s), it sounds like it might not be.

TC, i was meaning the gearing being too numerically low as the issue for a 2500-2800 stall.
Scott, i couldn't tell he was shifting, it was smooth/quiet and I expected the shift kit to hit hard.He felt it shift, if he didn't mention it i never would have known!

David

Well thanks for all the info everyone.Turns out the stall was working as it was supposed to but his car ended up lacking the driveability he was looking for, hence his dismay.He took the car in and i guess they misunderstood what his intentions were and are now installing a 1700 stall for him.

David