A question just to be sure.. Will a BOP TH350 converter work on a SP400 trans? I believe it will not, but to be sure let me know. Tnx Robert
The splines on the pump are different, too. The only way to make a TH350/TH400 fixed pitch converter work on a variable pitch trans is to switch input shaft & pump to the fixed pitch design. Devon
tnx guys for the reply, thats what I thought also. Ok, I know a SP400 converter for sale from my old race combo. Gonna give them a call.
I wanted to shoot a question out there and this was the closest related thread I could find to the question I had. My friend had a TH375 in his 72 GS. We want to swap in a BBTH400 and we've already gotten the correct length driveshaft due to the shorter TH400. The problem is that the converter no longer fits. Apparently the input shaft on the TH375 is different than that of the TH400 and the converter does not seat in deep enough to allow the bell housing to reach the motor before the converter comes into contact with the flywheel. There's an obvious difference in the spline length of the TH375 input shaft as compared to the TH400 input shaft. When fully seated into the TH375 there's about an inch distance between the bell housing bolt flange as compared to the TH400 when the converter is fully seated where there's maybe 3/8 of and inch distance between the converter and the bell housing bolt hole flange. Different converter needed?
I don't think so Ken. The converters for the fixed pitch 350 and 400 should fit the 375 with no problem. Sometimes it can be a bit of a problem to get them to seat. Look at the splines and make sure they are in good shape. Lubricate them with a little ATF. I like to line up the pump tabs with the slots in the converter hub, so I know that is in. Then keep turning and pushing until it drops down 2 more times.
I don't know Larry, we tried like all get out to seat this converter on the TH40 and did get two "clicks" to seat it but it just would not go in far enough. Look at these two pics below. The fist one is the TH375 input shaft, the second is the TH400. The coarse spline on the TH400 is about half the length of the coarse spline on the TH375. I'm thinking the converter is running out of spline to slide in on with the TH400 and hitting the part of the shaft that's un-splined. If it was able to go in the amount of distance further as the spline on the TH375 is longer, it would be perfect. The overall shaft length is the same, but on the TH375 notice the longer center spline. On the TH400 the center spline is about half as long.
Your last picture is of 65-67 switch pitch pump assembly. NOTHING but a switch pitch torque converter will fit it. Bruce Roe
Like Bruce said, the one with the shorter stator splines is a switch pitch. You can't put a fixed pitch converter onto a switch pitch input shaft, and visa versa. That 400 is a SP
Then I have a follow up question. What converter do we use and where do I find one? Or, what is needed to convert this tranny back to fixed pitch? I'm trying to get a pic of the BB tag on the side.
Ken, This thread put together, by Jim Weise, is very good. It helps to see the differences between converters and transmissions. http://www.v8buick.com/showthread.php?143723-VP-converter-Trans-visual-ID-guide There are plenty of switch pitch converters out there. The 12" is more desirable as it has higher stall speeds. I have one of Jim's 12" modified units and I love it. I still have the 13" SP converter that was originally in my car when I bought it. I would consider selling it. Stall speeds are approximately 2000/1100. To change over a switch pitch transmission to fixed pitch would involve swapping out the front pump and input shaft.
Do you think it's worth the hassle to swap the TH375 front pump and input shaft? How hard is it? I mean, both trannies are out now, but will a SP trans work correctly with a fixed pitch pump and shaft? Thanks for the link above. I will look at this too.
Not sure if the 375 pump is interchangeable with the 400 pump. Bruce could tell you. Don't know how difficult it would be to swap the pump and input shaft.
It's not cheap, but I think we may try to get a converter for the TH400. Look at the ID tag of the TH400. It's possible someone installed VP innards on it years ago. It's even got the two prong connector on the side of the tranny. I spoke with Jim W. at TSP about it tonight.
Well, I guess it's up to my friend as it's his tranny. But I would think as long as we get a solenoid click when energizing each of those pins on the side, then everything is functioning? Then maybe he'll go for the matching converter? Seems like so much work to start swapping pumps and input shafts. You know how that goes, it always ends up being more than you want to get into.
The SP is the ultimate Street/Strip Transmission. I love explaining to all the brand X ers. Some don't believe me, until I break out the documentation, and show them how it works.
Well, I might be back on here asking more questions about it, because even after reading the threads explaining it, I still can't seem to fully wrap my pea brain around how it works and if there's additional switches that need to be hooked up. Seems it works off the brake light switch but you can also install a manual switch if you want to engage the high stall at will? Do I understand this correctly?
Very simple. Apply 12 volts to the stator contact, and you get high stall. Remove the 12 volts, and it goes to low stall. How much simpler can it be. There are several different Timer boxes out there to control it. One was made by Jim Burek. It had 4 wired connections and it works very well. Don't know if you can still find them out there. Bruce Roe makes a more sophisticated box that has a vacuum input and 3 different timers. Or, you can simply hook it to the switched wire of the brake switch. When you step on the brake pedal, it energizes the switch pitch. You can hook up a momentary switch also. One side goes to 12 volts, the other to the transmission. Hold the switch when you want high stall, let it go when you want low stall. At the track, you want high stall for about 2 seconds, then low stall for the balance of the run.
