Band Clearance

[TexasT]

So, I'm doing some reading and I came across this thread.

http://www.turbobuick.com/forums/threads/proper-method-for-checking-band-clearance.10151/

I have conversed with others on the band setup and this is yet another way. I do have to ask, where are the shims added? I have just hit the end of the pin with the wirefeed and then made adjustments with a grinder and/or file.

TIA

 

[olds403]

I did it at the pin of the servo. Meaning, I added to the pin and subtracted as needed.

 

[Janis Transmission]

what band are you using

 

[TexasT]

I am using a stock width carbon band. I set it up with a little drag, and when air is squirted into the exhaust on the pan rail it clamps the thing and I can't turn the output with the yoke in it. We had it in and out several times without the springs n seals, then installed it all when I felt comfortable with the setup.

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[Janis Transmission]

I like about an 8th of an inch . shims go behind piston

 

[stovebolt 34]

Just got Chris's strong return spring ( I mean really strong ) . Got the transmision out and on it's back . Got the X plate in . Added one more shim to the piston pin . Seems to be right where Vince would want it . Got to take it out and put the seal and cushion spring in . Will see what happens . Just wondering if anybody else has as much trouble as me getting the snap ring back in the groove . I always get it done but it's a pain in the butt . I've tried several different pairs of pliers .

 

[TexasT]

I guess that is why gm made a tool to press the piston and cover in there. I have read of others who use a big prybar and something to fulcrum on small enough to get the ring around it and use the trans tunnel to pry against to get the piston in far enough to get the retainer in. Did I explain that right? Sounds hard but with some dexterity or a helper with an extra set of hands not as hard as it sounds.
I do think I didn't have near .125, mine was much closer to .060 . I hope I don't burn it. We will see.

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[Steve V]

Remember guys...every trans builder has there own way. I suggest you stick with one way and one band.

Where are you guys getting these shims? I just use what I have lying around the garage. I am pretty much out so next time I will need to go shopping first.

Last trans I did was carbon band and heavy drag per Dave. No issues. I have another set up the same way and it's still on the bench I will install it maybe in the spring.

 

[Alky V6]

Keep in mind that a short pin will demand more servo travel and the servo return spring will have to be compressed more before the band clamps.
The more the return spring is compressed in order to clamp the band, the more return spring pressure you will have fighting against your apply pressure.
Adding shims on the piston end to take up servo travel will still leave you with a return spring that is compressed more than has to be before the band is clamped. If you are using a stiff, high rate return spring, you don't want to compress that spring more than you have to during band apply.
The best method by far to take up excess servo travel is to add material to the band end of the pin, then grind whatever is needed until you have the target servo travel. Every builder will prefer his own target servo travel. I would not have more than .125". I use .080" - .100". The 2-3 shift is a synchronized shift, so the amount of travel in the band servo and in the high/rev drum does play a big part in how well the 2-3 shift feels and lives.
Aftermarket servo piston manufacturers go to great lengths to increase servo apply area to the limits to provide more apply pressure to the band. Why would you kill all that hard work by causing the servo return spring to have to be compressed more than it has to be? Don't use shims. Lengthen the pin.

 

[TexasT]

I guess that's why I asked though I didn't think of it in such detail. I just used the return spring that came with the 569 servo. Is the return spring different for this , the 692 and the 694? I'm using a sonnax servo and the pin that came with it but we did "adjust" it for clearance. Obviously(or I guess) the ck spring is heavier than all the stock springs, right? I guess I am counting on a layer of fluid on the drum when the band is disengaged to combat it from dragging. Is this a wrong assumption?

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[TexasT]

[quote="Steve V, post: 3354239, member: 11]

Last trans I did was carbon band and heavy drag per Dave. No issues. I have another set up the same way and it's still on the bench I will install it maybe in the spring.[/quote]
Was that a wide or stock width? Which servo did you use? Nice crisp shift? What about down shift? Did you measure clearance at all or just did it by feel?

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[stovebolt 34]

As they say , more than one way to skin that proverbial cat . I see where you're coming from on the short pin strong spring . I got the strong spring cause Chris says with a billet servo and. Big boost valves you will have band drag . Oh we'll .

 

[Steve V]

[quote="Steve V, post: 3354239, member: 11]

Last trans I did was carbon band and heavy drag per Dave. No issues. I have another set up the same way and it's still on the bench I will install it maybe in the spring.

Was that a wide or stock width? Which servo did you use? Nice crisp shift? What about down shift? Did you measure clearance at all or just did it by feel?

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Carbon band stock width. There's no clearance to measure cause it has "heavy drag". Stock servo. Shifts are nice.