Anyone Change Converters From Precision To 9.5" PTC?

[GNVYUS 1]

Curious as I'm going this route in probably a week.

Any track info, MPG difference, cruise rpm change, throttle response, trans temp, whatever else?

 

[bison]

You would have to be more specific about the Precision. There are several different ones out there. They worked well in high rpm solid cammed engines but had a hard time coupling with high boost when the cars are trapping 130+ with hyd cams unless they were multi-disc lock ups. Ive yet to see anything come close to a 9.5" PTC. Every car i put one in or rec'd to someone else got the exact result i expected. I never kept track of mpg biut ive hot 20+ cruising with the 9.5" in my black car. Throttle response is more dependent on the tuner and the octane used. Better tune with more octane and aggressive timing will net better response and power at all angles. Trans temp is not a problem as long as cruising speed is reasonable. If your going to be cruising at 80+mph all the time you need to have a really good cooler and keep an eye on trans temp. Run dex 6. It takes heat better than just about anything.

 

[GNVYUS 1]

Forgot to add that I have the 5 disc.

I've read a few posts from you Bison about how much you like them and how well they've performed. I'm looking forward to driving one next weekend and moving forward this year with 0 issues.

 

[bison]

Forgot to add that I have the 5 disc.

I've read a few posts from you Bison about how much you like them and how well they've performed. I'm looking forward to driving one next weekend and moving forward this year with 0 issues.

If your gearing and tire is optimal you should pick up substantially in the 330' with the 9.5".

 

[BEATAV8]

Curious as I'm going this route in probably a week.

Any track info, MPG difference, cruise rpm change, throttle response, trans temp, whatever else?

You can expect to hold 1st and 2nd gear longer, and you will probably have to recalibrate your valve body. Mine went from shifting by itself at 5750 @ 55 MPH to shifting a 5200 @ 55MPH. I had to switch to a KC valve body to get the RPM's back up around 5800, but now at 80MPH. That's a lot more MPH in 2nd gear... which is a good thing.

 

[TurboBob]

You can expect to hold 1st and 2nd gear longer, and you will probably have to recalibrate your valve body. Mine went from shifting by itself at 5750 @ 55 MPH to shifting a 5200 @ 55MPH. I had to switch to a KC valve body to get the RPM's back up around 5800, but now at 80MPH. That's a lot more MPH in 2nd gear... which is a good thing.

I have been thinking of switching to a KC or other alternate VB, and when I get the 9.5" PTC it sounds like the thing to do.

But, the BRF in my car now does the light throttle 2-3-2-3-2-3-2-3 sometimes, and nobody in the transmission community has offered a real fix. So (pardon the thread hijack), did you ever have the 2-3 busy-ness, and is it better/different now? How do the part throttle shift points feel now relative to a BRF?

Bob

 

[BEATAV8]

I have been thinking of switching to a KC or other alternate VB, and when I get the 9.5" PTC it sounds like the thing to do.

But, the BRF in my car now does the light throttle 2-3-2-3-2-3-2-3 sometimes, and nobody in the transmission community has offered a real fix. So (pardon the thread hijack), did you ever have the 2-3 busy-ness, and is it better/different now? How do the part throttle shift points feel now relative to a BRF?

Bob

My old BRF did that too, and my wife's blue car also does that with the BRF still, but the olds VB hasn't done that to me yet. The accumulator is still present in the circuit, so the part throttle shifts are smooth.

 

[Ed Valvo]

Bob,
My PTS trans did that. I pulled a couple clicks out the TV and it went away. Have you tried that?

 

[TurboBob]

tried that

I have tried all the TV setting suggestions by everyone, and all it does is change when it happens.

I have been thinking of changing to a CZ valve body, or perhaps a KC to see if it helps.

Looks like it might....

Bob

 

[bison]

I have been thinking of switching to a KC or other alternate VB, and when I get the 9.5" PTC it sounds like the thing to do.

But, the BRF in my car now does the light throttle 2-3-2-3-2-3-2-3 sometimes, and nobody in the transmission community has offered a real fix. So (pardon the thread hijack), did you ever have the 2-3 busy-ness, and is it better/different now? How do the part throttle shift points feel now relative to a BRF?

Bob

What spring is on the 2-3 shift valve?

 

[TurboBob]

I don't know.

The trans was build by Brian Hofer. I am not sure about his valve body calibrations.

In digging up data on the valve configurations, the hysteresis of the 2-3 shift at light throttle looks to be more a function of the diameter of the lands, and not the spring. I would love to measure the 2-3 valves of the BR, CZ and KC someday.

But if you have a fix for this, lets talk..


Bob

 

[bison]

I don't know.

The trans was build by Brian Hofer. I am not sure about his valve body calibrations.

In digging up data on the valve configurations, the hysteresis of the 2-3 shift at light throttle looks to be more a function of the diameter of the lands, and not the spring. I would love to measure the 2-3 valves of the BR, CZ and KC someday.

But if you have a fix for this, lets talk..


Bob

Im in the process of moving but when im done i can measure the diameters of the shift valves. I dont currently have any KC vb's on hand to measure that are not on the shelf.

 

[TurboBob]

cool, thanks!

Bob

 

[GNVYUS 1]

"Mine went from shifting by itself at 5750 @ 55 MPH to shifting a 5200 @ 55MPH"
Whoa, that's a big difference, I wasn't really happy with my current rpm shift so thanks for the heads up.

1st I've heard of swapping valve bodies for the change in converters, hopefully Jimmy has a grasp of this.

 

[BEATAV8]

"Mine went from shifting by itself at 5750 @ 55 MPH to shifting a 5200 @ 55MPH"
Whoa, that's a big difference, I wasn't really happy with my current rpm shift so thanks for the heads up.

1st I've heard of swapping valve bodies for the change in converters, hopefully Jimmy has a grasp of this.

Ya the improved coupling really reels it in. Jimmy and I installed the KC valvebody in my trans. I don't know how many he has done since then.

 

[JDSfastGN]

"Mine went from shifting by itself at 5750 @ 55 MPH to shifting a 5200 @ 55MPH"
Whoa, that's a big difference, I wasn't really happy with my current rpm shift so thanks for the heads up.

1st I've heard of swapping valve bodies for the change in converters, hopefully Jimmy has a grasp of this.

I had the same issue, my shifts were 5600-5700 before on an old pro-torque and after the PTC it was 5100. I just installed a slightly modified KC valve body and could not be happier. 5750-5800 on the shifts.

 

[GNVYUS 1]

BEATAV8, did Jimmy have that in stock or did you have to get one first?

Also, was he not comfortable grinding away at the governor spring to get the shift rpm up?

 

[BEATAV8]

BEATAV8, did Jimmy have that in stock or did you have to get one first?

Also, was he not comfortable grinding away at the governor spring to get the shift rpm up?

I bought the valve body from CK perf and brought it down by Jimmy. He was skeptical at first but after it was installed and we went for a ride he decided he liked it. The valve body had 2 major differences compared to the previous BRF VB.
1. 5800-6000RPM automatic WOT shifts with reasonable TV settings, can get to 6200+ with the TV fully tight. This comes from the KC valve body itself combined with the stock BR governor. (and combined with a good torque converter like the PTC)
2. 2-3 upshift super solid at WOT (no RPM flare at all). This comes from removal of the 3-2 downshift valve from the hydraulic circuit. Bison and Chris told me to go with this and it works. From what I heard, some old school factory GM transmission engineer knew about this and told Chris or somebody about it.

Jimmy was not really into grinding on the governor, as it can require several attempts to get it right. I did not think it was good solution either, as the governor can ger really light and potentially erratic. The valve body is the way to go. Drives great, and works great at WOT.

 

[turbogray]

so you just remove the 3-2 downshift valve ?

 

[BEATAV8]

so you just remove the 3-2 downshift valve ?

No it's more complicated than that. You need a valve body plate from CK perf and the 3-2 downshift valve gets some special treatment. Best to talk with CK performance about it.