Hey all,

I am replacing the transmission in my 84 T/A. The 1-2 and 3-4 is starting to slip pretty bad when I get on it. I have to baby it around for it to actually shift.

I picked up a 1990 2wd 700R4 (Well, numbers were shaved off but it does have the elctronic VSS in the back of it so should be an 88+) and want to get a lockup torque converter to replace the stock converter I'm running now.

This winter I'm going to have my new tranny rebuilt and will be putting a new converter on it so I started searching here on the boards for info regarding converters. It seems like Vigilante, ATI or Circle D are the only way to go from what I'e learned of who to buy from. After that, my question is how do i determine which stall to get? I've read two things about choosing a converter's stall speed, both here on the boards. The first is a that I want to shoot for 400-700 rpm above the power band of the cam. The other is to match it to the peak torque RPM of the motor. Now, just having dyno'd my car, my torque spiked up and seemed to hold steady from around 3200ppm all the way to 5000rpm where it fell off the wagon.
If I use the first theory, with my cam's rpm power band being 1800-6000, means I would get a stall around 2500rpm, maybe a little less. This seems more suited to street use. This is primarily going to be a street car and I don't want to go around smoking the tires off of it every time I hit the throttle.

Using the peak torque theory, I should get my converter to stall around 3000-3200 rpm. Probalby better for track yes but less so for street use?


I could use a little advice from those in the know. Options, opinons, thoughts, general BS? Thanks.

Full list of engine mods:
- Edelbrock Performer Intake
- World Sportsman II Heads, 2.02 int/1.60 exh, 64cc chambers
- 9.3:1 compression pistions, no idea what my final compression ratio is, sorry
- Lunati 60121 Cam...specs:
•Advertised Duration (Int/Exh): 270/278
•Duration @ .050 (Int/Exh): 219/227
•Gross Valve Lift (Int/Exh): .515/.530
•LSA/ICL: 112/106
•Valve Lash (Int/Exh): Hyd/Hyd
•RPM Range: 1800-6000
- 3.73 Gears
- Headers, 3" catback
- BeCool Aluminum radiator, I will be getting an aux cooling unit for the trans

Any input would be greatly appreciated! Thanks!

 

No one has any ideas?

 

I think you nailed it. Alittle over cam powerband is better for street driving. Less initial slip when pulling out from a stop, or climbing hills when converter is unlocked.

By your dyno results, 3200-3400 is pretty good for best track numbers. Could even try 3500. Its been said few hundred rpm below peak torque is where you wanna be for track performance but some put it around peak trq rpm.

So you decide what you want the most. I personally would go 2800-3000 for more street car use. Especially if you are not used to driving stalled cars. It is different and takes some getting used to. I ran 2800 in my stock L98. Car was absolute blast. I daily drive 3200 in my bolt on Ls1 which makes peak trq closer to 4000-4200. Its also a good match and fun car

Make sure you get a lock up style converter. Drives like stock once locked

 

Thanks for the reply! I will definitely get a lockup. I'll shoot for 2400-2800 I think. 3000 may be a bit more than I'm looking for.

Would you get an auxillary trans cooler with a fan or without a fan?

 

Do you still have stock style cooling system lines that go thru rad?

If not then you can add a small cooler. Mount up front, no need for fan. It shouldnt get hot. My very loose stall th400 runs a b&m plate style cooler, one of their bigger ones and never gets over 180 deg even when beating on it

Now only one time did i think i overheated tranny abit with 2800 stall. It was an hr drive up the mountain and i was corner carving and on throttle alot! Motor was 220 deg and trans felt like it slipped. I let it cool for 15 min and felt fine after that. That was with a stock rad cooler system, 700r4

 

Yes, I'm currently running the factory lines through the radiator. I've read though that I should also run a secondary aux cooler whenever running an aftermarket torque converter. I currently have a plate style B&M cooler with no fan but it's not installed yet. Put it in front of the radiator?

 

It wont hurt but you likely wont need it if you arent constantly abusing it.

 

I say that parts combo needs a loose 2500 stall. Better a 12" than a 10", in this case. The real problem is those heads, I'd sell them then put that money and the converter money to some decent 180 cc heads. In which case I'd say the 10" converter would be good.

 

My farvorite saying.

"If I had known then.....what I know now"....I would have gone with a set of AFR heads instead of the World Heads. However, that's not the case and I have the money now for the Converter, which I won't if I buy a new set of heads.

Vigilante doesn't sell a 12" converter with a 2500 stall. I'd have to step way down to B&M or TCI and tha'ts not something I would like to do right now.

 

I agree. 2500 stall just isn't worth the cost of the swap. Go 2800 min. I wouldn't go much over 3200 if you're worried about too much stall. This sounds like a Circle D 2C converter would be the one you'd want.

 

I had good luck with Edge racing converters, medium price grade but worked well. One 2800 in 9.5" one 3600 in same housing and one 3200 in my ls1 which is also 9.5". I havent had any issues, but usually the lower stall speeds are larger diameter.

 

A converters stall speed is different behind different engines. The stall rating is only an estimated stall speed.

Now, a stall speed based on your camshaft would indicate that for best performance, a converter with a stall speed in the 2500-3000 range should be used. As mentioned above, I wouldn't go higher than 3000 and 2500 might be slightly low. 2800 will probably give you the best performance.

Doesn't matter what else you've done to the engine or the car. Best converter stall is based off the camshaft grind. Any other mismatching of parts won't change where the camshaft powerband is for the converter to use.

 

Bingo...

 

It looks like I will be going for a 2500-3000 Stall based on recommendations. I want good street manners, as mentioned, I want to get up an go but I don't want to smoke the tires off every time I hammer it. I'm sure I"ll find out more when I talk to the company about building the converter.

 

I agree. I have a Vigilante 3200 advertised that flashes to around 3000 and I definitely wouldn't want to go any higher. The slipping is most noticeable in OD unlocked. I can bring it up to 3500-4000 in OD when my actual mph locked would put it at 2000 rpm.