Help with TH400 trans - having converter issues

[TTA850]

I'm having a problem or at least I think I'm having a problem with excessive converter slippage in high gear and wonder if anyone else has gone through this or has an opinion.

I'm running a TH400 w/brake and a PI Vigilante converter(non lockup)that they said is approx 3000 stall which is irrelivant becuase with the brake I am leaving at like 4000+rpm's(15+ pounds of boost) - does that sound right?

Now my concern is my rpm's through the traps and the fact that I'm getting around 21-22mph out the back.I was told I should see around 25mph which should put me in the 118-120mph range.Problem is I'm turning 5200-5300rpm's at 116.xxmph when I should be closer to 122.xx at those rpm's(with a 7% slip factor).Keep in mind I have 3.08 gears and have yet to run anything more than a street chip and pumpgas because I'm afraid of running out of rpm's if I switch to racegas.

Here are my two best runs:
60ft - 1.578
330 - 4.668
1/8 - 7.290@93.02
1000 - 9.575
1/4 - 11.517@115.52

60ft - 1.586
330 - 4.671
1/8 - 7.285@93.27
1000 - 9.564
1/4 - 11.498@116.19

Now,using this website http://www.smokemup.com/auto_math/mph_range.php I've figured out that my converter is slipping like 12-14% in high gear - which to me does not sound right.What should a properly built converter slip?I was told 5-7% max.I have already sent this converter back to PI and they tightened it up a bit(brought the slip down from approx 17% to 12-14%)and I picked up two mph and went from a best of 11.78 to 11.49 so I think I'm heading in the right direction with this.

Sorry for the long post but I'm not sure where to go with this and have lost my faith in PI - but don't know where to go from here.I have heard alot about Neil Chance,anybody using one of his?Any other suggestions?

Thanks in advance,
Steve

 

[6PacktoGo]

The converter is too loose. And you'll never get decent slippage numbers with a 3.08 gear.

 

[TTA850]

I was wondering if the 3.08 gears were a problem or not,but here's my thing - I really don't want to spin this thing more than say 5500 and if we assume the car will pick up around 10mph when it's fine tuned on racegas then it should go around 126.When I did the math 5500rpm's with a 26" tire and 3.08 with 7% converter slip would put me at 128 - this however goes out the window with 12-14% slip I'm seeing now.

I could switch to 3.25's but I'd have to run a 28" tire which I figure would put me back in the same boat as if I keep the 3.08's

I dunno,just getting tired of ripping the trans out of the car so many times and still it's not right.

Steve

 

[Eric Stage I]

I use an ATI 9" 3500 stall converter (I've not had it up to 3500 yet, my brakes aren't holding very well). I'm using 26" tall ET Streets and turn 5600-5700 through the lights at 123mph. I guess thats 3-4% slip. I've been very happy with this converter so far. By the way, I'm using a TH350 tranny .

Eric

 

[TTA850]

Eric,doing the math you are right in the 3-4% slip range which is excellent and where I want to be.

I've heard good things about ATI myself and if you don't mind I have a few questions for you.

For one,where did you get the converter?Do I or should I contact them direct for more information?

How much stall can you get it up to and how much boost at that point before it pushes?

Thanks,
Steve

 

[6PacktoGo]

If I remember correctly, Eric bought his from me. Last summer. I've been an ATI dealer since 1984.

 

[Eric Stage I]

Yep, got it from Alan. Good experience. He quoted me a price, but after looking at my combo, he recommended a different size converter which was more expensive. He ate the difference to honor my original quote! (It was over $100 difference as I recall.)

My brakes don't hold very well, but I just went out and recorded some data on the e-brake for you.

2500 0psi
3100 5psi
3500 8psi
3500-3600 overcame the e-brake at 10ish psi.

I asked for a stall of 3500 when I ordered it, and it looks like its pretty darn close.

Eric

 

[TTA850]

I'm thinking I need a similar converter - I originally asked for 3000-3200 or so.

Alan,in your opinion can it be made to work with the 3.08's?I'd probrobly need something a little tighter than Eric's in the stall department.I'm not looking for 3-4% slip(though I must admit thats impressive )but around 6-7% max.My combo is basically in my sig,the car is 3600lbs raceweight w/driver and I may switch to a lower 1st gear while I have the trans out.

After looking at ATI's website I like whatg I see.I'm not looking to buy right now but will about when the racing season ends(mid November)so I won't mind downing the car to rip the trans out again.If you could,give me a ballpark on what tyoe of converter I'd be looking at and around what dollar figure(not looking for something carved in stone or anything),and keep me in mind cause I'll most likely be contacting you in a month or so about getting one.

Thanks in advance,
Steve

 

[6PacktoGo]

I'll be glad to get you a quote, just email me. I don't think that they can do one tighter than Eric's 9", that converter has been a killer in four cars, but they said that it is on the limit as far as getting it any tighter.

One other thing, with a turbo, once you get boost, you can blow right through a converter if you have a brake. You have to be careful, because you just keep making more power and forcing more stall.

 

[Chuck Leeper]

VERTER PROBS!

YEP!

 

[TTA850]

Ok sounds good,I'll be in touch with you in a few days.And thanks again

Steve

 

[Turbo231]

Your times look like mine did a few years ago.
I had a PI "6" pump stall rated at 4k
my data logs showed my motor never went below 5800 from start to finish.
I swaped it out for a "0" pump PI stall and picked up 0.5 sec and dropped about 1500 RPMs.
It was a day any night difference.
You might just send your stall in and have it changed.
I changed mine three times but I'm glad I did.