200-4R 2nd Band Release hole

[jthomas]

Can anyone tell me which hole is specific to the 2nd Band Release?

 

[Clark6]

hmm maybe the experts will chime in .... what are you trying to do specifically?? But I thought the servo piston had to do with the band release?.. Ck's book says 3rd gear oil pushes the servo piston back towards the cover to release the band... So don't quote me on this but is it possible that its the 3rd accumulator hole?? #5 on your diagram?? I'm still trying to learn this stuff myself.....

 

[jthomas]

hmm maybe the experts will chime in .... what are you trying to do specifically?? But I thought the servo piston had to do with the band release?.. Ck's book says 3rd gear oil pushes the servo piston back towards the cover to release the band... So don't quote me on this but is it possible that its the 3rd accumulator hole?? #5 on your diagram?? I'm still trying to learn this stuff myself.....

Thanks Clark6. I know you are right about #5 being a critical orifice size in the 2-3 shift. I had a mild bind on mine after dual feeding the directs and solved it with the help of Lonnie and David by plugging the large #5 and drilling the small #5 to .120". I also plugged the large #14 and drilled the small #14 and did the 3-2 control mod. That eliminated my bind completely. A friend of mine has a similar bind on his and I figured since it worked for me we would do the same to his. He is also dual fed and has the Sonnax super servo. It definitely helped, but he still has some bind compared to mine. I had read about enlarging the 2nd servo release hole but wasn't sure if they were referring to #5. If so we already did that. We could drill #5 from .120 to no more than .125, but I'm not sure if that little bit would make much difference. My pressures are higher given Lonnie's pump, but he does have very good pressure on his. Maybe that little bit of an enlargement might help. We should check his servo travel too. He may have his tighter than mine.

 

[Clark6]

When you say bind does that mean after it shifts from 2nd to 3rd it noses over just a tad before it changes? I got a little bind in mine & that's the best I can describe it... I don't think mine was drilled. I'm gonna measure to be for sure though.
Also which one is the 2nd servo release hole?

 

[jthomas]

When you say bind does that mean after it shifts from 2nd to 3rd it noses over just a tad before it changes? I got a little bind in mine & that's the best I can describe it... I don't think mine was drilled. I'm gonna measure to be for sure though.
Also which one is the 2nd servo release hole?

On mine it was at medium light throttle where it felt like the second gear band was still holding when the 3rd gear clutches engaged, then the band released just a hair late. If I let off the throttle just as the shift was happening I could get it to do a pretty tight bind, like being in 2nd and 3rd at the same time for a second. The mods I did fixed it.

The question you asked about which is the 2nd servo release hole is the same question that prompted me to post. David Husek called me after I posted this and confirmed it is a combination of #5 and #14 that are key to the timing on the 2 release / 3 engage. In addition to plugging the 5 large round hole, he suggests drilling the small #5 hole and small #14 hole. From what I gathered though these mods are only if you have dual fed the directs. He also mentioned dual feeding tends to enhance the bind so check ball delete at 14 and 16 lb springs in the direct help too. Sounds like all the expert builders have slightly different methods to solve the problem, some more successful than others. I'm certainly no expert on all of this, just really interested in learning and fine tuning. Mine is good now and my friends is much better than before the mods, so I think I'm going to call it a success.

 

[Clark6]

k thx Yeah Daves a big help ive bought lifters from him on my car n asked for other advice also...hey how do you plug the holes in 5 & 14?

 

[jthomas]

...how do you plug the holes in 5 & 14?

I used some aluminum plugs that I got from a guy at our local AAMCO. He is the go to guy around here for transmission modification parts. Some shift kits come with plugs too.

 

[77 cruiser]

They come in Trans Go kits & are for that purpose of plugging #5.

 

[Clark6]

Ok thx Jim . I also talked to Lonnie today. Things are a little clearer now. )

 

[Ttype6]

Heavier than stock 3rd gear return springs help the bind by slowing down the engagement of the 3rd gear clutches. You must use these springs if dual feeding. The other thing we can do,to coordinate the apply of the clutches and the release of the band,is to speed up the release of the band. We accomplish this with the 3-2 mod and by using a heavier than stock servo return spring. Dave can supply you with a heavier return spring. This timing problem is created by dual feeding. Because we are now applying force to twice the area on the direct apply piston,the 3rd clutches apply faster which messes with the coordination of these 2 events. The two things we can do to restore the timing of these 2 events it to slow down the apply of the direct clutches and speed up the release of the intermediate band.

 

[Ttype6]

The other thing going on here that changes 3rd gear timing is the larger diameter aftermarket servo.The band apply side of the servo piston has a larger diameter than the stock GN piston. The release side of the piston remains the same as stock. This slows down the release rate of the band because the difference between the diameters of the apply side of the piston and the release side of the piston aren't as great as they used to be. During a 2-3 shift,the apply side and release side of the piston receive the same amount of pressure. What makes the piston move in the direction that releases the servo? The piston moves because the release side of the servo piston has a larger diameter than the apply side. The same amount of pressure acting an two surfaces that have two different amounts of area will exert more force on the larger surface. Since the release side now has a lesser percentage of increased area over the apply side,the piston moves slower to release the band than it did with the stock servo. So,another possible solution is to re install the stock servo. Using a stronger servo return spring however should get you where you need to be

 

[gunzandgearz]

The other thing going on here that changes 3rd gear timing is the larger diameter aftermarket servo.The band apply side of the servo piston has a larger diameter than the stock GN piston. The release side of the piston remains the same as stock. This slows down the release rate of the band because the difference between the diameters of the apply side of the piston and the release side of the piston aren't as great as they used to be. During a 2-3 shift,the apply side and release side of the piston receive the same amount of pressure. What makes the piston move in the direction that releases the servo? The piston moves because the release side of the servo piston has a larger diameter than the apply side. The same amount of pressure acting an two surfaces that have two different amounts of area will exert more force on the larger surface. Since the release side now has a lesser percentage of increased area over the apply side,the piston moves slower to release the band than it did with the stock servo. So,another possible solution is to re install the stock servo. Using a stronger servo return spring however should get you where you need to be

Not bad ttype6 great explanation as you have obviously done your homework,great job,this comes from the hydraulic formula fap which means force is equal to area times pressure which means that if the same amount of pressure is pushing on two separate pistons, but one is larger than the other, the larger piston will apply more force than the smaller one.

now in saying that,once the 2-3 shift happens, the hydraulic pressure starts decreasing on the apply side and increasing on the release side as the hydraulic fluid has now been closed off on the apply side of the servo. The problem with this is that we have now introduced something in the system that the factory didn't calibrate for which is a larger piston apply area which gives us more apply force on the band for greater holding capacity or clamping force on the direct drum.This is great for us as when we start pumping out more power we need this higher clamping force on the drum for the higher torque output we are putting to these trannies. The issue that we have introduced into the hydraulics part of this circuit is a timing issue,as we now have more force on the apply side of the piston than what gm designed in but the same on the release side, so the way we fix this issue is by getting the fluid to the release side of the piston faster i.e. larger orifice (hole) in seperator plate and or stouter release spring or both,this way we don't get that dreaded 2-3 bind up that everyone talks about.

 

[jthomas]

Heavier than stock 3rd gear return springs help the bind by slowing down the engagement of the 3rd gear clutches. You must use these springs if dual feeding. The other thing we can do,to coordinate the apply of the clutches and the release of the band,is to speed up the release of the band. We accomplish this with the 3-2 mod and by using a heavier than stock servo return spring. Dave can supply you with a heavier return spring. This timing problem is created by dual feeding. Because we are now applying force to twice the area on the direct apply piston,the 3rd clutches apply faster which messes with the coordination of these 2 events. The two things we can do to restore the timing of these 2 events it to slow down the apply of the direct clutches and speed up the release of the intermediate band.

The other thing going on here that changes 3rd gear timing is the larger diameter aftermarket servo.The band apply side of the servo piston has a larger diameter than the stock GN piston. The release side of the piston remains the same as stock. This slows down the release rate of the band because the difference between the diameters of the apply side of the piston and the release side of the piston aren't as great as they used to be. During a 2-3 shift,the apply side and release side of the piston receive the same amount of pressure. What makes the piston move in the direction that releases the servo? The piston moves because the release side of the servo piston has a larger diameter than the apply side. The same amount of pressure acting an two surfaces that have two different amounts of area will exert more force on the larger surface. Since the release side now has a lesser percentage of increased area over the apply side,the piston moves slower to release the band than it did with the stock servo. So,another possible solution is to re install the stock servo. Using a stronger servo return spring however should get you where you need to be

Thanks Ttype6...nice comprehensive explanation of all the factors affecting the 2-3 shift. Appreciate that you took the time to share this.

 

[jthomas]

Not bad ttype6 great explanation as you have obviously done your homework,great job,this comes from the hydraulic formula fap which means force is equal to area times pressure which means that if the same amount of pressure is pushing on two separate pistons, but one is larger than the other, the larger piston will apply more force than the smaller one.

now in saying that,once the 2-3 shift happens, the hydraulic pressure starts decreasing on the apply side and increasing on the release side as the hydraulic fluid has now been closed off on the apply side of the servo. The problem with this is that we have now introduced something in the system that the factory didn't calibrate for which is a larger piston apply area which gives us more apply force on the band for greater holding capacity or clamping force on the direct drum.This is great for us as when we start pumping out more power we need this higher clamping force on the drum for the higher torque output we are putting to these trannies. The issue that we have introduced into the hydraulics part of this circuit is a timing issue,as we now have more force on the apply side of the piston than what gm designed in but the same on the release side, so the way we fix this issue is by getting the fluid to the release side of the piston faster i.e. larger orifice (hole) in seperator plate and or stouter release spring or both,this way we don't get that dreaded 2-3 bind up that everyone talks about.

Thanks for the additional information gunzandgearz. It all makes good sense, but can you confirm which hole in the separator plate is related to the release side of the piston?

 

[gunzandgearz]

Thanks for the additional information gunzandgearz. It all makes good sense, but can you confirm which hole in the separator plate is related to the release side of the piston?

I'm not really sure what you're asking,as Dave pretty much already answered.The fluid comes in from the manual valve at square hole 8 and from there it goes to the small hole 8 thru a worm passage in the case. This is where it (the fluid)hangs out at the stop light (2-3shift valve) until it's opened by governor pressure where it goes on to become direct clutch oil. From there it goes to 14 small and large holes on your plate,this is where ball #4 is that Dave said to remove because it just gets in the way and restricts oil flow on a hi perf. Trans.From here it moves on to large single hole 14 and into case where check ball #6 sits, from here it's routed to the direct clutches thru center support, the fluid is also routed to orifices #5 which goes into 3-2 control valve passage.and into the 3rd accumulator/servo release circuit.This is why Dave said to deal with holes 5 and14 as these are the only ones of concern, but also where the 3-2 control mod comes into play as the fluid can go a couple of different ways depending on where the 3-2valveis sitting as gov. Pressure controls where the valve is and where the fluid goes this is why it is blocked in a lot of applications and the orifices are drilled and plugged as to not allow it to be variable.I don't know if this answered your question but as stated there is not just one orifice totally responsible for fixing this bind problem,this is why Dave talked about orifices 5 and 14 as they are the important ones.

Thanks for the additional information gunzandgearz. It all makes good sense, but can you confirm which hole in the separator plate is related to the release side of the piston?

 

[jthomas]

....I don't know if this answered your question but as stated there is not just one orifice totally responsible for fixing this bind problem,this is why Dave talked about orifices 5 and 14 as they are the important ones.

You did...thanks for recapping the details as it clarified the full path start to finish. The reason I asked that question again is you made a comment in the earlier post: "so the way we fix this issue is by getting the fluid to the release side of the piston faster i.e. larger orifice (hole) in seperator plate and or stouter release spring or both...". That statement had me wondering if there was another hole in the separator plate playing a role in the band release other than the combination of 5 and 14 that was already covered.

Since we did all the same mods to my friends tranny which fixed my 2-3 bind, I think your comment about a stronger servo return spring would be an easy next step. I will suggest he try that now.

Thanks again to everyone. Great information in this thread!

 

[jthomas]

Deleted duplicate post

 

[SS/GN]

I think there is an advantage in the Sonnax servo for this because the pin is clipped to the piston allowing for faster and more positive release of the band.