LH23H2R
Well-Known Member
Oh , okay . Thanks !
I was thinking about the Low Gear Block Out on Police / Taxi models ; my Coronet has one .
Why a Reverse Valve Body?
- Thread starter Mopastor
- Start date
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Oh , okay . Thanks !
I was thinking about the Low Gear Block Out on Police / Taxi models ; my Coronet has one .
moper
Well-Known Member
There's some partial information here... Sorry, it's wordy...lol
The main reason for the manual shift cretion as I understand it was quickening the shifts. Reversing the passages for first gear vs third shortens the fluid path between 2nd and 3rd and also removes the possibility of 1/2 shift overlap when the low/rev band is applied in factory stock manual low gear. Mopar calls it "Breakaway First" when you place the trans in "1" with the gear selector. In a factory valve body, engaging "1" engages the forward clutch pack and the low/rev band. The band backs up the sprague, or overrunning clutch, in break-a-way first. It should be noted the sprague is the only fixed (not fluid activated) holding component for first and second forward gears. It does not hold anything in third. Inside the valve body, the fluid has to go around a maze of casting to get from one shift valve to another before it heads out to the various servos or clutches. So no matter how much you want to speed things up in terms of 3rd gear activation, you can't unless you shorten the distance between the shift valves. By reversing the path that fluid taes throught he valve body, you quicken the response time to the shifter input. When we drill the casting with that special jig when doing adding shift kit, we're doing a similar thing. Bear in mind we're talking hundreths of a second but if the trans slips for .05 second at full throttle every time you upshift, after a season that friction is trashed. So the trick is no overlap, no slippage. that's the "why" behind a reverse pattern manual valve body.
On the tranny explosions...
Now because the typical (Cheeta, DC tech papers) valve bodies do not use the band in first, the risk of messing up the sprague is inreased. It can be damaged when the tire speed is faster than the engine speed (like if you let off during a burnout in first or second instead of powering out or if you slip the tires in the rain and let off the gass to let them "catch up"), or when the force through the sprague is interrupted like when a rear shears teeth or fails. So they call them not for street use. The way to minimize the possibility of explosion due to sprague failure is to buy the "low band apply" manual valve bodies. Cope sells a good one but there are others too. Some are forward (factory) pattern, some aren't. All they will do (at teh expense of the ultimately fastest shifts) is apply the low/rev band in first. They dont help with the sprague in second. They dont stop the explosions simply by using them. That's because to stop the explosion, you have toreplace the explosive...
The factory forward clutch retainer (that means forward in the case, not forward gears, because it actually is engaged in reverse too...) is a powered metal manufactured part. It's light and cheap, and plenty strong. When you read about "adding clutches" or the "Hemi band and clutches" thats the part that is different. The problem with the powdered metal drum is is cannot safely spin beyond about 8K rpm. Normally, because it'sonly used in 3rd, it would never spin that high. However, in first gear, there is nothing holding it still except that rear sprague. And it's held through a series of mechanical gears. So, if the sprage fails, the gears in the connection begin multiplying the engine rpm as it's applied to the drum. When the engine's at 3K rpm (like foot braking the stall, or on the trans brake, or just as you let off the brakes on a street car) the drum can be spun to over 12K rpm. It explodes around 10,000 rpm, and the force is the same as a stick of dynamite surrounded but steel. The way to permanently fix the explosion deal, and remove the risk entirely, is to have your transmission built with a billet steel or aluminum forward clutch drum. Then you can still break the sprague, but you wont lose a foot, rip the unibody apart, or kill a spectator if you do.
The main reason for the manual shift cretion as I understand it was quickening the shifts. Reversing the passages for first gear vs third shortens the fluid path between 2nd and 3rd and also removes the possibility of 1/2 shift overlap when the low/rev band is applied in factory stock manual low gear. Mopar calls it "Breakaway First" when you place the trans in "1" with the gear selector. In a factory valve body, engaging "1" engages the forward clutch pack and the low/rev band. The band backs up the sprague, or overrunning clutch, in break-a-way first. It should be noted the sprague is the only fixed (not fluid activated) holding component for first and second forward gears. It does not hold anything in third. Inside the valve body, the fluid has to go around a maze of casting to get from one shift valve to another before it heads out to the various servos or clutches. So no matter how much you want to speed things up in terms of 3rd gear activation, you can't unless you shorten the distance between the shift valves. By reversing the path that fluid taes throught he valve body, you quicken the response time to the shifter input. When we drill the casting with that special jig when doing adding shift kit, we're doing a similar thing. Bear in mind we're talking hundreths of a second but if the trans slips for .05 second at full throttle every time you upshift, after a season that friction is trashed. So the trick is no overlap, no slippage. that's the "why" behind a reverse pattern manual valve body.
On the tranny explosions...
Now because the typical (Cheeta, DC tech papers) valve bodies do not use the band in first, the risk of messing up the sprague is inreased. It can be damaged when the tire speed is faster than the engine speed (like if you let off during a burnout in first or second instead of powering out or if you slip the tires in the rain and let off the gass to let them "catch up"), or when the force through the sprague is interrupted like when a rear shears teeth or fails. So they call them not for street use. The way to minimize the possibility of explosion due to sprague failure is to buy the "low band apply" manual valve bodies. Cope sells a good one but there are others too. Some are forward (factory) pattern, some aren't. All they will do (at teh expense of the ultimately fastest shifts) is apply the low/rev band in first. They dont help with the sprague in second. They dont stop the explosions simply by using them. That's because to stop the explosion, you have toreplace the explosive...
The factory forward clutch retainer (that means forward in the case, not forward gears, because it actually is engaged in reverse too...) is a powered metal manufactured part. It's light and cheap, and plenty strong. When you read about "adding clutches" or the "Hemi band and clutches" thats the part that is different. The problem with the powdered metal drum is is cannot safely spin beyond about 8K rpm. Normally, because it'sonly used in 3rd, it would never spin that high. However, in first gear, there is nothing holding it still except that rear sprague. And it's held through a series of mechanical gears. So, if the sprage fails, the gears in the connection begin multiplying the engine rpm as it's applied to the drum. When the engine's at 3K rpm (like foot braking the stall, or on the trans brake, or just as you let off the brakes on a street car) the drum can be spun to over 12K rpm. It explodes around 10,000 rpm, and the force is the same as a stick of dynamite surrounded but steel. The way to permanently fix the explosion deal, and remove the risk entirely, is to have your transmission built with a billet steel or aluminum forward clutch drum. Then you can still break the sprague, but you wont lose a foot, rip the unibody apart, or kill a spectator if you do.
moper
Well-Known Member
I'm pretty sure this prevents the trans from downshifting into first when the engine would be pushed over it's redline. It means they can't "kickdown" or shift to first while in Auto (drive) if they are going over around 40 depending on the rear gear ratio.
R5P7Duster
358 ci Nightmare
I have reverse VB and have a clean neutral after drive. Works great.
So the shift pattern is P-R-1-2-3-N
Maybe you'd like that?
Whose shifter do you use with that? Which brand of valve body?
R5P7Duster
358 ci Nightmare
I was told to never start out in 2nd gear. I can't remember why, but I do remember the trans has to start turning before it hits 2nd otherwise there could be catastrophic failure. Maybe it's the rule for just my VB but I was told to start in 1 then shift to 2nd then come out of the burnout.
Rick Allison built my valve body. The guy knows his stuff...
R5P7Duster
358 ci Nightmare
I have a PPP shifter http://www.precisionperformance.com/home.htm
And I have a custom built VB by Rick Allison from A&A trans http://www.aandatrans.com/
Here's the best pic I have of it...
R5P7Duster
358 ci Nightmare
Thanks, one of these days I'd like to clean up the wiring and get rid of the stock underdash wiring and just run the required wires that I need.
The car is still street legal, if you were wondering why I still had the wiring in.
The car is still street legal, if you were wondering why I still had the wiring in.
Guitar Jones
aka Angry Johnny
needsaresto
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I think it's never do a burnout in first due to the Sprag wanting to do 12000 rpm or something like that. With a 727 always burnout in second.
Dorian
dorian
Come on guys easy fix...
put in a 4 speed!!!
we all know real race cars have a clutch !!!!
put in a 4 speed!!!
we all know real race cars have a clutch !!!!
superbird6bbl
Well-Known Member
Excellent observation.You no longer need kick down linkage, but I bet you still want to connect your throttle.
superbird6bbl
Well-Known Member
I have raced from 1970 to 1993 and then started back again in 2009. I have never exploded a Torqueflite. I have always started the burnout in 1st gear and shifted on up through 2nd then drive and then let it roll out from just in front of the standing water. I did dry hops for 23 years, but I have stopped doing them now. Yes, Rick Allison is one of the best.
R5P7Duster
358 ci Nightmare
No, never start out in 1st, maybe you just got mixed up.
I'll call rick tomorrow and get the answer why not to start out in 2nd.
R5P7Duster
358 ci Nightmare
Ok just got off the phone with Rick from A&A.
Guitar Jones is 100% correct in 99% of applications.
In my application, where we drag race on ice the trans will spin up so fast in 2nd gear and rattle the sprag so hard it could fail which Rick has had experience with in mud drag racers and boats. And he was applying this to my application as well, due to the burnouts preform.
Rick stated that in asphalt racing Guitar Jones is 100% correct and this procedure should be followed to prevent trans failure.
Here is a video so you guys can kind of understand how fast these cars rev on the ice....
[ame="http://www.youtube.com/watch?v=ibvhMVTiUu8"]YouTube - R5P7 Duster running the Modified class week 3 2011[/ame]
Guitar Jones is 100% correct in 99% of applications.
In my application, where we drag race on ice the trans will spin up so fast in 2nd gear and rattle the sprag so hard it could fail which Rick has had experience with in mud drag racers and boats. And he was applying this to my application as well, due to the burnouts preform.
Rick stated that in asphalt racing Guitar Jones is 100% correct and this procedure should be followed to prevent trans failure.
Here is a video so you guys can kind of understand how fast these cars rev on the ice....
[ame="http://www.youtube.com/watch?v=ibvhMVTiUu8"]YouTube - R5P7 Duster running the Modified class week 3 2011[/ame]
viperredduster
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I have never seen anything like that. That is pretty wild stuff
dustoff440
Well-Known Member
I have Cheetah valve body which has the disadvantage of not being able to downshift into first. I love the pattern though. P R N 123. It feels more natural to pull the shifter towards me instead of upshifting towards the dash. The major advantage to me is that there is no way I can accidentally shift into neutral in the heat of the moment. I also like being able to bark the tires on command. It's not a daily driver so I don't ever get tired of shifting. I would have bought a different one but I got this brand new still in the box for 80 bucks....
It was also my understanding that installation of a manual valve body would not only produce neck snapping shifts and absolute control of the tranny but would also increase transmission life, not to mention elimination of the Rube Goldberg downshift linkage.
It was also my understanding that installation of a manual valve body would not only produce neck snapping shifts and absolute control of the tranny but would also increase transmission life, not to mention elimination of the Rube Goldberg downshift linkage.
fishy68
Tyr Fryr's Inc.
The Trans-go kit is just a kit to improve shifts, not a complete valve body. All stock units have low band apply so installing a Trans-go kit does not affect that. For a mild setup, regardless of engine size, I'd use the Trans-go TF-2 kit.
fishy68
Tyr Fryr's Inc.
Yes. But again it's a modification kit you add to your stock valve body. It does not eliminate manual low band apply. Just because a valve body is full manual shift doesn't mean it doesn't have low band apply.
It's real funny nobody's gave the one answer to the original question that's probably the most popular and correct one. Why a reverse valve body? Probably cause that's what somebody wanted to buy.
I recently bought a bunch of stuff from a guy for my drag car, a '70 Dart which will have a 440 and 727. Included with the parts was a Cheetah manual reverse valve body. The instructions dont mention band apply in 1st, but do say 1st gear, no engine compression braking. Does this mean no band apply in 1st? If not, how can I modify it to apply?
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