I am a chevy guy but would love to get some info from you guys on what performance to expect from converting to a switch pitch tranny. I currently have a 408 sbc that is making about 450hp. I am running a TH400 with a BTE 3500 10" converter. I am considering going the switch pitch route for better street manners but still a hard launch at the track. If I were to go to a PAE or like converter with say a 3500 stall on high stall what kind of difference could I expect in the ET at the track?? I plan to add a gear vendors OD in the future so the 3500 stall would be slipping to much. So in short I guess I am asking will the car slow down with the switch pitch with the same amount of stall?? What type is more efficent?? Thanks guys!
Very good question! I'm no torque converter wiz, but I would expect that running at high stall using a 3500 vp converter vs a standard 3500 rpm converter would yield the same net effect in performance. Another interesting question (to which I don't know the answer) is what effect on ET/MPH would there be using the low stall after initial launch, either positive or negative? I'd think there might be some improvement if the converter is in the low stall (more efficient) mode down the track, maybe all by itself, maybe also with tire height/gear ratio tuning. Hmmmmm.... Devon
I have a switch pitch in my car. The switch pitch converters are heavier than a fixed pitch converter. For racing, the fixed pitch trans is the better choice. It will give you more consistency at the track. I'm not sure, but your ET might increase somewhat. Low stall might give you a higher trap speed though. Don't get me wrong, I love my switch pitch, but if the car is mostly strip, the fixed pitch is better. For the street, nothing beats the SP versatility. For the GV, you'll need the switch pitch, or lower stall for sure.
Thanks guys for the repsonse. My car is mostly street but would like to go to the strip maybe once a month. Looking for high 11 second times. I was just worried if I went the switch pitch route the car would drop ET. Has anyone went from a fixed pitch high stall to a SP and lost ET ?? Thanks guys anymore info would be great!
I took this from Jim Weise's website, www.trishieldperf.com He discusses what your asking about here: "This is often know as a "switch pitch", which is a term that was popularized by Kenne-Bell, back in the seventies. GM engineers called it a "Variable" pitch, as the origin of the name relates to the "variable" angle of the torque converter's stator blades. This transmission is preferred for street cars, that see the drag strip once or twice a year. Mainly drag raced vehicles, will benefit from the proper fixed pitch converter, over a VP unit. This is fact that was proved many years ago, regardless of the "hype" you might hear. If you think otherwise, then how can this question be answered: IF a VP trans was the "Ultimate trans for a race car" then why did none of the major manufacturers reproduce it?? Surely, with the millions of TH400's in use, by enthusiasts and racers, they could have realized a tremendous profit, regardless of the investment it would require. There are two reasons for this: Consistency- Regardless of what type of control system is used, the converter's stator return, from high to low stall, is rather time inconsistent. That's not good, if your trying to "run the number". Converter weight- 11,12, and 13" converters are heavy. A good 8, 9 or 10" converter is considerably lighter, which allows the engine it rev faster, which in turn, makes the car faster. Simple as that. That being said, don't get us wrong. We love the VP setup for a street car. So much so, we developed the only furnace brazed, high quality torque converters on the market now. It adds a "neat" dimension to your project, and allows the advantages of a higher stall converter, without the excessive heat buildup, and slippage."
Thanks Larry,Good info! Im not going to running in any type of index class were I need to be right on the number...like a 11.90 or 10.90 index class. I was looking for something that will be more streetable and still runs similar times low 12's to high 11's. Say the car ran 11.90's with the fixed pitch I just didnt want it to drop to like 12.50's cause of the change. I will give trishield and PAE a call and see what they kind of loss or gain I might expect. But this is for sure 80 percent street and 20 percent track type car. Thanks again for the help guys!
contact Jim B, you'll love his trans and converter for the type of driving your doing. My over 4000lb GS has had one of his TH400SP's in it for about 1 1/2 years now. No problems at all with lots of abuse. I'm running the quarter in high to mid ll's at over 120mph on street tires. I love the Trans and in my book there's not a better pick for those that like mellow crusing, and hard launching.
Thanks Rich! That looks like the route I will most likely end up going . When you contact Jim B that is TSP right??? I looked at the web site but does not give any info on converters. What low/high stall are you running??
I was refering to Jim Burke (PAE) I'm runing a 1300low 3000high setup and love it. I sould also add my Mid 11's are ran at 5000ft above Sealevel and haven't been corrected in anyway --Rich
Thanks Rich....Hmm I might need a bitter looser on both high and low stall ratings. When just crusing around in low stall I down want to tight at the stolights to idle right. Maybe something like a 2000/3500..??
6D9 i had a switch pitch 400 behind a healthy 455 that i used to run at the track once in a while..at first i left it in the high stall position for the whole run. car launched good and felt pretty good through the whole run. then i tried turning the converter to low stall after aprox 60' and before it shifted to second gear.. i gained 2 tenths of a second and 3 mph. this was a car that ran 12.10-12.30 i would agree that it isnt the most consistent way to go but it sure did work for me. Bob
Then you need to do what Buick did originally...wire the high stall to be engaged at idle as well. You can do it with a microswitch on the throttle linkage (Buick's method), or even set it up so that it's in high stall when the brake lights are on. :Brow: Devon
my converter was a stock buick converter out of a 66 skylark with a 300 engine. i had it rebuilt with torrington bearings and low stall was about 1500 and high stall was 3000 rpm. i used to fool a lot of people when street driving cause i would leave the low stall turned on and i had a remote timing control inside the car. i could advance the timing enough to smooth out the idle and with it turned to low stall setting the car sounded near stock. as soon as i had them suckered into racing me i switched the timing back and set the converter back to high stall. got me a lot of 5.0 mustangs and chevrolet guys that way..they always swore i had nitrous but i always proved them wrong :grin:
6D9, I did not see your name in any of your posts. Anyway, I'm Jim Burek from P.A.E. Enterprises. In answer to some of your questions, the s-p will give better mph than a conventional converter when in low stall. We also make a timer for turning off the converter at the same point, this makes for a very consistant set-up. My car typicaly will run within .001 to .002 seconds with a s-p. We are also the only company to offer an 11 inch s-p converter, which is lighter weight than the factory 12 inch and especially 13 inch units. I have always run the s-p converter in my personal car. I did one test some years ago in my car with a 3500 stall 10 inch vs my 11 inch series s-p. The car was .3 seconds faster in the quarter and over 4 mph faster in the quarter with the s-p. I did not like driving the car with the 10 inch 3500 stall in it. If it were'nt for s-p's , I would most likely be runnin g a manual trans. Jim Burek P.A.E. ENTERPRISES 915-855-6009
