Full Manual Valve Body?
Thread Starter
Safety Car
Joined: Oct 2004
Posts: 3,926
Likes: 739
From: Youngstown Ohio
Full Manual Valve Body?
Is anyone running a full manual valve body on their street cars?...either forward or reverse shift pattern? My Turbo 400 has to come out to repair a front seal leak, so I'm going for a rebuild while it's out. Being a street/strip car, I'm thinking performance. Besides always having to shift, any regrets that I might encounter? Do you have to downshift a certain way when braking? Thanks for all info and replies.
Racer
Joined: Jun 2005
Posts: 400
Likes: 11
From: Lubbock Texas
I used to have one in my 70 SS Chevelle. Mine still had the standard shift pattern. No problems with it at all. You do not have to downshift when braking if you don't want to. If you are cruising down the street in 3rd gear & stop for a stoplight, if you did'nt drop it back in first it would just take off in 3rd. So what ever gear you have the selector in is the gear it stays in. I don't know of any real advantages to it ( It was in the car when I got it) but it was fun.
Racer
Joined: Apr 2005
Posts: 464
Likes: 0
From: Charleston South Carolina
I have the foward pattern in my th350 and a 3500 stall, there is no decelleration when going from 3rd to 1st but only from 3rd to 2nd. I find it to be a smoother shift if when I'm in 3rd and I am going into a right turn, I drop it to 1st and quickly bring it up to 2nd to get the braking effect. I love it. I can go as fast as I want in 3rd and when I drop it in 1st to stop at a light there is no braking effect unless I bring back up to 2nd.
Race Director
Joined: Nov 2002
Posts: 12,142
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From: Taylor Michigan
Safety Car
Joined: Oct 2000
Posts: 3,593
Likes: 103
From: Southern Indiana
First gear is really neat.
You can nail it and let off the gas and it just goes back to idle.
You can also amaze your friends taking off in 3rd and sounding like a 5000 stall!
The shift when you want to.
Down side= shifting all the time.
You can nail it and let off the gas and it just goes back to idle.
You can also amaze your friends taking off in 3rd and sounding like a 5000 stall!
The shift when you want to.
Down side= shifting all the time.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
I fail to see any advantage with the "manual" shifting set-up with an automatic. I can select when to upshift with the standard system. I can also downshift as I choose (notwithstanding the downshift inhibitors in the valvebody which prevent overspeeding). The only thing that I can't do is start from a dead stop in 2nd gear or 3rd gear...and I don't know why I would ever want to do that.
Safety Car
Joined: Oct 2000
Posts: 3,593
Likes: 103
From: Southern Indiana
A car with 465 gears will shift out too soon before the RPMs are built up enough.
Also a big cam will make the car lose vacuum to the modulator and then not shift at all at full throttle.
I also think a turbo 400 will shift 2nd to 3rd even if you only have the shifter in 2nd.
There is lots of advantages to a manual valve body you just have to need them!
Also a big cam will make the car lose vacuum to the modulator and then not shift at all at full throttle.
I also think a turbo 400 will shift 2nd to 3rd even if you only have the shifter in 2nd.
There is lots of advantages to a manual valve body you just have to need them!
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Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
A THM 400 will stay in range until the appropriate "shift" valve is tripped by governor pressure. If your engine turns high RPM's and the transmission wasn't matched to it, you have to change the shift valve springs and reset the shift RPM's from 1-2 and from 2-3. To my knowledge, any automatic set-up is designed to shift to the next highest range, if a given rpm limit is reached...even your "manual" set-ups. {Check with the vendor to find out.}
Safety Car
Joined: Oct 2000
Posts: 3,593
Likes: 103
From: Southern Indiana
To my knowledge, any automatic set-up is designed to shift to the next highest range, if a given rpm limit is reached...even your "manual" set-ups. {Check with the vendor to find out.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
No one designing [or re-designing] a shifting system for an automatic tranny wants to build-in a situation where "Bubba" leaves it in a range to the point of overspeeding a transmission. The original THM 400 was only built to take so many rev's...in the neighborhood of 6000. You could get the auto with the low revving 454, but not with the LT1; it could take the torque and horsepower just fine...it couldn't take the high rpm's of the LT1.
So, the shift valve system is designed to "force" a shift to the next higher range, even if the shift lever is held in range. If you stick a THM400 (or any automatic tranny) in first range and wind the he!! out of it, when it gets to a certain rpm, IT WILL SHIFT TO 2ND....you can't prevent it. No tranny builder want his unit to overspeed the converter, etc. and have it come apart underneath someone driving/riding in the car.
So, the shift valve system is designed to "force" a shift to the next higher range, even if the shift lever is held in range. If you stick a THM400 (or any automatic tranny) in first range and wind the he!! out of it, when it gets to a certain rpm, IT WILL SHIFT TO 2ND....you can't prevent it. No tranny builder want his unit to overspeed the converter, etc. and have it come apart underneath someone driving/riding in the car.
Safety Car
Joined: Oct 2000
Posts: 3,593
Likes: 103
From: Southern Indiana
No one designing [or re-designing] a shifting system for an automatic tranny wants to build-in a situation where "Bubba" leaves it in a range to the point of overspeeding a transmission. The original THM 400 was only built to take so many rev's...in the neighborhood of 6000. You could get the auto with the low revving 454, but not with the LT1; it could take the torque and horsepower just fine...it couldn't take the high rpm's of the LT1.
So, the shift valve system is designed to "force" a shift to the next higher range, even if the shift lever is held in range. If you stick a THM400 (or any automatic tranny) in first range and wind the he!! out of it, when it gets to a certain rpm, IT WILL SHIFT TO 2ND....you can't prevent it. No tranny builder want his unit to overspeed the converter, etc. and have it come apart underneath someone driving/riding in the car.
So, the shift valve system is designed to "force" a shift to the next higher range, even if the shift lever is held in range. If you stick a THM400 (or any automatic tranny) in first range and wind the he!! out of it, when it gets to a certain rpm, IT WILL SHIFT TO 2ND....you can't prevent it. No tranny builder want his unit to overspeed the converter, etc. and have it come apart underneath someone driving/riding in the car.
I knew it was one way or the other, I just couldn't think how it went!
I remember having a 400 and it was shifting without me going out of 2nd, and thinking the cable was un-adjusted.
Thread Starter
Safety Car
Joined: Oct 2004
Posts: 3,926
Likes: 739
From: Youngstown Ohio
No one designing [or re-designing] a shifting system for an automatic tranny wants to build-in a situation where "Bubba" leaves it in a range to the point of overspeeding a transmission. The original THM 400 was only built to take so many rev's...in the neighborhood of 6000. You could get the auto with the low revving 454, but not with the LT1; it could take the torque and horsepower just fine...it couldn't take the high rpm's of the LT1.
So, the shift valve system is designed to "force" a shift to the next higher range, even if the shift lever is held in range. If you stick a THM400 (or any automatic tranny) in first range and wind the he!! out of it, when it gets to a certain rpm, IT WILL SHIFT TO 2ND....you can't prevent it. No tranny builder want his unit to overspeed the converter, etc. and have it come apart underneath someone driving/riding in the car.
So, the shift valve system is designed to "force" a shift to the next higher range, even if the shift lever is held in range. If you stick a THM400 (or any automatic tranny) in first range and wind the he!! out of it, when it gets to a certain rpm, IT WILL SHIFT TO 2ND....you can't prevent it. No tranny builder want his unit to overspeed the converter, etc. and have it come apart underneath someone driving/riding in the car.
Sorry to disagree, but I have personally known folks who have blown an engine by not shifting their automatics manually out of 1st gear before 7000+ rpms. It won't shift on its own regardless of high rpm...you must move the lever when manually shifting.The ideal situation is having the governor calibrated for the exact desired shift points (which is my goal), so I can just put it in "D" and steer down the track ......perfect shifts, no staring at the tach.
I do like the idea, though, of doing away with the vacuum mod. and wondering if this would give me cleaner quicker shifts; and if so, would it be worth a quicker ET.
Thread Starter
Safety Car
Joined: Oct 2004
Posts: 3,926
Likes: 739
From: Youngstown Ohio
Mine has a shift kit installed, so that must explain the ability to hold each gear to engine failure when manually shifting......
Race Director
Joined: Nov 2002
Posts: 12,142
Likes: 54
From: Taylor Michigan
I dont hsve the slighest idea where someones elses turbo 400 shifts at but mine shifts where and when I want. none of that pressure 
BTW, i`m sure you all know or maybe forgot about it but in 1969 a turbo 400 was available with a L89 engine. The first time GM coupled a solid lifter BB to a automatic.
BTW, i`m sure you all know or maybe forgot about it but in 1969 a turbo 400 was available with a L89 engine. The first time GM coupled a solid lifter BB to a automatic.
Thread Starter
Safety Car
Joined: Oct 2004
Posts: 3,926
Likes: 739
From: Youngstown Ohio
I dont hsve the slighest idea where someones elses turbo 400 shifts at but mine shifts where and when I want. none of that pressure
BTW, i`m sure you all know or maybe forgot about it but in 1969 a turbo 400 was available with a L89 engine. The first time GM coupled a solid lifter BB to a automatic.
BTW, i`m sure you all know or maybe forgot about it but in 1969 a turbo 400 was available with a L89 engine. The first time GM coupled a solid lifter BB to a automatic.
Even bone stock, my TH 400 shifted where and when I wanted when shifted manually. I always shifted at 6500-6700 RPMs when racing.......no involuntary "shifting on its own".
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Shift rpm's for range overrides are established by spring strength on the range shift valves. One could set that by selecting the appropriate spring. If GM put the THM transmissions behind a high winding engine as part of normal production, I'm not aware of it. Anyone rebuilding an auto tranny can change the springs and get it do to whatever. But if they are using a stock GM torque converter and internal parts with stock balance tolerances, the driver is braver than I am. Racing transmission rebuilders installed sturdier converters and components along with the spring changes to allow higher rpm shifts [that were safe].
Race Director
Joined: Nov 2002
Posts: 12,142
Likes: 54
From: Taylor Michigan
Shift
If GM put the THM transmissions behind a high winding engine as part of normal production, I'm not aware of it. Anyone rebuilding an auto tranny can change the springs and get it do to whatever. But if they are using a stock GM torque converter and internal parts with stock balance tolerances, the driver is braver than I am. Racing transmission rebuilders installed sturdier converters and components along with the spring changes to allow higher rpm shifts [that were safe].
If GM put the THM transmissions behind a high winding engine as part of normal production, I'm not aware of it. Anyone rebuilding an auto tranny can change the springs and get it do to whatever. But if they are using a stock GM torque converter and internal parts with stock balance tolerances, the driver is braver than I am. Racing transmission rebuilders installed sturdier converters and components along with the spring changes to allow higher rpm shifts [that were safe].
Burning Brakes
Joined: Feb 2005
Posts: 1,235
Likes: 0
From: Mesa AZ
The first Vette with a high performance 427 engine to receive a turbo 400 was the L89 version of 1969`s introduced in September 1968. Actually one very rare combination of approximately less than 20 or so built in the 1969 model run. Appropriately equipped with a higher stall converter for ease of idle control. But this we all knew was necessary anyway. However I personally beat GM to the punch a couple of times with a L88 and another with a L72. Those 400`s make great racing transmissions. Much quicker than standard anythings for basically stock cars. Hell, early Chevy powered funny cars even used them