Was wondering about the benifits of a SP Converter. Are they hard to use or work with? How do they work on the street? Is a regular converter better? So many questions, and you are the people with the answers.
I've got one in mine and I like it. I don't race, so I can't testify about that application. What I like is the smoother idle quality with the mild cam I am running. The added torque multiplication helps the performance too, in my opinion.
Im getting ready to build my SP400 but as a testiment, I have a buddy of mine with a mild 455 and a SP with a 1800/4500 stall, lifting the front tires off the ground wiht his Fullsize LeSabre.. with AC intact and working. I cant wait!!!! -Jon
For a street car, a switch pitch is the ultimate transmission IMHO. For a race car, a fixed pitch is better. SP converters are heavier. On the street, if you have sticky tires, you can launch the car in high stall, then switch back to low stall once the car is moving. Same thing at the track. I have a switch pitch controller box that works on a timer, and is hooked to the brake pedal. The timer is adjustable from 0-11 seconds. When your foot is on the brake, the converter is in high stall. When you release the brake, the timer counts down to zero, and puts the converter into low stall. Completely hands free. You would set it for your 60' time at the track, or further out if you like. The box also has manual control. I have the TSP 12" converter in my car. I can't say enough good things about it. It is everything JW said it would be and more. The high stall is 3200, and the low stall is 1800. On the street, I just leave it in low stall. My KB118 cam will idle at 750 in gear, in low stall. It will still spin the tires with ease. Like I said, the SP is the best of both worlds, performance, and economy in one converter.
The switch pitch is "Jekyl and Hyde" for your Buick. It isn't the answer for a race car. It is hard to be consistent even with the timer. Not the best choice for bracket racers either. I installed one in my car for two reasons. First, it was a Buick only deal, nobody else had it. Granted it was in cars earlier than mine but I always thought it was something that was very "Buick". What I mean by that is, it offers you typical Buick luxury cruising when in low and bad a$$ Buick bruising in high. Second, is the actual application on the street. There is nothing better than a 3000 rpm stall when you need to make a point:laugh: and nothing better than sending the wife and kids off in a car that can be driven normally( yet runs low 12's). It gives you the choice between mild and wild without having to commit to one or the other.
i love the s/p set up, i went from a 3000 to a 4000, the 4000 works much better for me now, the 3000 was fine when my car ran mid 13s and was racing with drag radials. its just like the claims say, 2 trannys in one, it drives around town like a normal transmission and then you have a race tranny at the flick of a switch.
I have one on my daily driver w/ 455. You couldn't pry it from my hands unless I was dead. It's the only way to go for a fast street car. -Bob Cunningham
hey guy's what kinda rpm are you turning going down the road cruisin, i have 3.73 and was curious to hear .
it would be the same as a non switch pitch tranny, i have 3.73 and i think i turn about 3000+ at 70 with a 27'' tire
Mine is a 2.56 rearend, so getting some high stall at launch is extra important. I'm about 2500 RPM at 75 MPH, about 3000 at 90. Low stall is very important for this rearend ratio. -Bob C.
Two corrections here, the s-p was not a Buick only deal, it was used by olds and cadillac as well. The other point is I have never found the s-p to be inconsistant et wise. I have raced with a s-p setup since the late 70's and my car would run within .03 all day long throughout out the entire race, time trials through eliminations. We used to joke at the track that they could calibrate the clocks off the dang Buick, it was so consistant. Inconsistancies can be more prevalent when trying to operate the s-p with a manual switch, especially a foot activated switch because in the heat of battle, there is no way you can consisitently get to that button at exactly the same time run after run after run. Jim Burek
In response to the question about RPMs, I am not sure. I put a 2004R in mine, with a 2.56 rear and a 2000 stall converter. At anything from 60-80 it is doing around 2200 RPM. I would like to do the rest of the drive train right when I drop the 455 in. I really like the low RPMs at cruise, but this may be too low. I definatly think I would prefer a stock converter, and this SP converter y'all are talking about sounds intriguing. Will a SP converter with say, 1500 / 2500 stall work on 2004R, or am I not understanding what these things are?
Stan, You don't understand. You can't use a switch pitch converter in anything other than a switch pitch THM400, or 300. The SP transmission has a different front pump and input shaft. The stator vanes inside the converter change their angle, giving two stall speeds. You can convert any 400 over to switch pitch operation. There are conversion kits available. If your 200R4 was not beefed up, don't expect it to last long behind a healthy 455. If you add a Gear Vendors overdrive to the SP400, you would have a much sturdier transmission and the overdrive gearing. Do you have an accurate Tachometer? There is no way your engine RPM's stay the same between 60 and 80 MPHo No: With a 2.56 rear and the .67 overdrive 4th gear, that's 1.71 final drive ratio. That's extremely tall gearing. At 80 MPH, with that gearing, you should be turning about 1800 RPM@80 MPH
Larry, thanks for the explanation, that helps. The 2004R is a beefed up model from TPI, I was thinking ahead when I got it to make sure it would hold up. It is doing about 2200 at 80. I think the converter is just slipping below that with some gas being applied. At 65, when gas applied, it will sit between 2000 and 2500, depending on how far I push the pedal. If I let off, it drops to around 1500. It seems to me that at 65, though, the lockup converter should be applied. I am starting to think that isn't working. It came with the kit from TPI to apply the lockup at cruise. I wonder if it is possible to splice into the lockup wire to an idiot light, that would lite up when the lockup clutch was engaged. That would tell me for sure.
Stan, I agree, your lockup converter is not working. seems like the converter is slipping excessively also. Do you mean TCI? They make some tough transmissions, but I'm not sure it's beefed enough for a 455. Meanbuicks on this BB works at TCI. You might try PM'ing him.
TPI Performance - http://www.tpiperformance.com/ Maybe I should call these guys, and double check my installation. I'm learning as I go here, so I might have hooked something up wrong.
Maybe the stall on that converter is too high to pull that tall 1.71 overall gearing, without the lockup. Does it slip less in 3rd gear?
No, 3rd gear is about the same. I'll get a hold of TPI and see if they have some tips about all this. I would like a lite that would lite up when the converter is locked up, so I can tell for sure. I plan to beef up the rear end when I do the engine swap, sounds like I really need a steeper gear in there, maybe like a 3.08 or something in that neighboorhood. I mainly use the car for cruising 60-80, or around town, not a racer, so I'm not looking for race gear ratios.
