I've got a 10" converter that stalls at 3000 rpm.

The car is the 72 in the sig. Its a stock 502, with 3.55 gears.

The converter slippage is kind of a drag on the highway, so I was thinking of dropping down to a 2500 stall, but I don't want to slow it down, on the track.

I was even thinking of keeping this converter and going the 3.73 gears but I'm not sure if that will give me what I want either.

I've got a good sized transmission cooler, but the slippage is something new to me. My other cars have had stock converters, or have a clutch.

I think what I really want is an overdrive 4 speed with a lock up converter, but I know it'll be a while before I can save enough to do that with the other projects I have in mind.

are you really unhappy with the rpm your turning at highway speeds and kinda thinking its convertor slippage? even with 3.55 gears you are turning at least 2700 rpms at 60 and 3100 rpms at 70 with an est. 26.5 tire.

and with 3.73 gears this will be around 2850 at 60 and 3300 at 70 mph.

so you will just add even more rpms............

about the only real time i notice a looser stall is when pulling step hills down the road, at cruise speed its pretty "normal" i think, i have a tci 10" that brake stalls at 4500 rpms and have had several 12 to 10" convertors, even with my z28 with 2.41 gears and 2.73 gears with 2800 stall it still held nice at 2100 rpms with 2.41 gears and 2500 with 2.73 gears at highway speeds.

if you still feel its convertor slippage thats giving you the rpms at speed then maybe a 2500 rpm convertor might still give you what your looking for and if you get a good unit you might even gain some top end in the 1/4 because you will have less slippage at full throttle.

Thanks Dennis,
I was just wondering if a converter should stall right at what is supposed to be the torque peak, or if it would be more optimal to be slightly below, so that torque peak would be moving the car, and lowering the highway rpm slightly.

I live in PA so we have a bunch of hills. (My home is 800 ft. above my work)
On long grades it just seems like its slipping baddly under 3000 rpm.
I'm running a 28" (275-60-15) rear tire, and calculated 2,557 rpm at 60 mph.
(Didn't know what percentage to use for converter slippage)

Maybe I'm going faster than I think,
maybe its just the nature of high stall converters,
maybe I'm just used to the manual in my 68, but the 72 feels sluggish until 3000 rpm.

I've had the trans rebuilt recently, and the thought of spending the money on another rebuild is kinda unapealing, so if its slipping too much I figure thats not a good thing.

Been thinking about a road trip to CB 2006, and scared of making such a long run in a car that might not be up to long hours on the highway.

Its funny the 72 is more that a full second quicker than the 68 yet the 68 feels quicker.
I thought a low 12 second car would be a thrill ride, but its almost boring. Just aim gas it and bump the lever twice.
To run a mid 13 in the 4 speed 68 is far more exciting/challenging.

Its funny the 72 is more that a full second quicker than the 68 yet the 68 feels quicker.


That proves the butt dyno theory ;)

I thought a low 12 second car would be a thrill ride, but its almost boring. Just aim gas it and bump the lever twice.


As heavy as these cars are, a 12 second pass with an automatic is pretty uneventful, unless you're on street tires, That will make your sphincter pucker!! :D

A lot of the higher power cars go to a tighter/ lower stall converter so they don't drive thru them.

Thanks for the reply Bob,
I've checked out your car in the past, and have been impressed by its performance and appearance.

My 12.19 was on TA drag radials.
I've been thinking cam or nitrous, for next year, leaning toward nitrous, since its likely to be a little easier, and it won't hurt street manners.

Thats the idea with the thoughts on the converter, didn't know if I'm leaving torque on the table with a stock 502. And if a tighter converter could make it both quicker and more pleasant on the highway, it would be totally worth it to me to make the swap.

Was thinking about the tight ATI 10" tech guy told me it'd stall about 2400-2500 rpm. I've been reading about this stuff for a while but have fairly little real experience.

ass dyno :D
I agree completely.
My old 4 speed 70 SS396 with 4.10 gears sure was a blast and had a great seat of the pants feel,although it was quite a bit slower than the black cherry car at the track,which is as Thad mentioned about his own car,feels boring.Floor it,click the shifter twice and thats it.I guess that's why some guys keep wanting to go quicker.
Me,I just bought a Grand National instead..probably isn't quicker than my 70but has a tremendous seat of the pants feel that certainly builds your ego ;) :D

Thad,sounds like you need a quality convertor like an ATI as you mentioned,or a well built 2004R

What converter do you have now? My ATI 10" converter flashes to 35-3800 and is pretty streetable, but havent taken and won't take any longer trips with the solid roller, don't wanna wear out the springs, gotta save em for the track. It comes to a point when you have to decide what you want to do, go faster or be able to drive it anywhere you want. I want to get mine in the 10's year around and driveability is going away, some day I might go back the other way, I'm going to order an ATI 8" converter after the holidays and before the sale is over. I'd like to drop my 60ft down to mid 1.4x and e.t. in the 10.50-10.70 range. We'll see what happens, I hate working on my car in cold weather :(

Bob.....can you believe I've gone faster with absoluetly NO converter AT ALL! Why not call Coan, Winters or any of the serious trans/converter shops and get their opinion or talk to Bill and get some feedback......BTW....the rest of the combo?:beers:

Did it used to be an automatic Joe? ;)

Thad, it's a cross between the inherent nature of the converter, driving style and terrain. I live in east PA - a lot of hills here also. I find the 10" converter to be too loose for my tastes also. Even with the 408 motor, 3.73's and the reworked 10" converter, I think it is just not responsive enough at lower RPM's. When I install, the bigger motor, one of the things on my list is a different type of converter. I am considering a converter rated for towing - higher than stock stall with high torque multiplication out of the hole, but then has good lockup. I think with the weight of these cars, you almost have to set them up like you are going to be driving a truck - for street manners. Would be a completely different ball game if these were Nova or early Camaro's. Check out Transmission Speciaties, look under towing.