If I upgrade to a sonnax billet 4th servo in conjunction with a corvette 2nd servo, should I continue to use the shims supplied in the transgo hd2 kit?

 

I always do and normally get at least one in there. Just remember as long as you can turn the output shaft in both directions its not to tight! Also make sure that the snap ring is fully seated so you do not break the case. Hope this helps. Vince

 

good day ,
vince glad to see you still come on-line and shine on us with you knowledge , hope everything is going well! best wishes to you!,

 

I remember not being overly confident in transgo's shim until there is X amount of play specification on the servo pin. I think I put two in mine but it had 130k miles on it at that point so I'm sure there was some normal wear and stretching to the band.


Vince I'm not going to argue your knowledge but if the band is shimmed as tight as you say, would it not tend to drag a little?

 

All is well and I do help where I can. Life is good these days and its nice to be learning new stuff! Thanks Vince

When I build 4l60e units for a performance application I normally set the band up pretty tight as far as spec's go. Normally they will stretch and I do not see an issue by doing this. Personally the issue with these units is not the band when built right its the 3-4 clutch. With that being said inside the case there is an orifice that sprays oil at the the band and reverse input drum when there is fluid pressure in the third accumulator circuit. I have seen very few band failures and so obviously it stays well lubricated.

With the transgo kit or even the sonnax kit they want the band setup with a certain spec so the timing of the release of the band and the apply of the 3-4 clutch works. Obviously most people installing this kit are not doing an overhaul but trying to improve their shifts. The best way to really see what the band is doing while making adjustments is to have the pan off. You can actually see the ends of the band between the pan rail and the valve body. By applying air into a bleed located in the pan rail you can actually stroke the band. This will show you how tight it really is.

As long as you see the band move within the spec's given normally you are fine. Problem is if the band is already damaged or the drum is warped its only a matter of time before it fails. The shims supplied are there to make the pin length longer without having to purchase a longer pin. This is actually a great way to do it IMO and saves money. Those shims cost penny's where a pin cost dollars if you see what I'm saying here.

The whole "make sure you can turn the drive shaft in both directions" theory, is to make sure that the band does not have the reverse input drum in a hold position all the time. Otherwise when you go to drive your vehicle it will have second gear starts or shift 2-4 when it should shift to third gear. Also if you happen to have the shifter in the D3 position leaving from a stop in second gear(band to tight), when the trans tries to shift to third gear you will either smoke the over run clutch, 2-4 band or the 3-4 clutch. I hope this answers your question. Vince