low-reverse servo piston breaks

[djwhog]

I have a 727 reverse shift pattern manual valve body trans. I have over the years had issues that cause the low-reverse servo piston to break. Case is OK, no excess wear in the bore etc. Other than that it has been one hell of a firm shifting and quick shifting transmission. Has the better planetarys, drums, bands etc. It is in a 64 Dart with a small block. The retainer and springs do not break, just the piston. Maybe I need a better than stock part?

What do you think is causing the breakage, or do I need to go with a billet servo or HD part? Is it just too high of line pressure or do I need a better part here in the trans or something I am missing?his is the only issue I have ever had withthe trans.

Note: I am going to do a complete rebuild because it is do, but while I have it out I want to eliminate this failure.

Thanks!

 

[Duster346]

The cast aluminum pistons can break with increased pressures from shift kits and aftermarket valve bodies. I would upgrade to a billet aluminum L/R piston.

Hope this helps.

 

[djwhog]

Are these pistons designed any different or just stronger? Anything else I should be looking at that may be a weak link while the trans is out?

I have seen that there are various designs to the piston and some people say it is because it gets cocked in the bore and breaks. But I think my issues is the line pressure.

Let me know what else you would reccomend because it is getting a 416 stroker in front of it in the 500+hp range now.

thanks!

 

[Mrmopartech]

Check out Art carr,s web site for pistons and the race versions.You could even have a machine shop with a CNC machine make a few for you with a modified version to stop the common breakage problem of cocking in the bore by having a extra ring land built into the piston skirt,to stop the cocking of the piston at the top of the bore,which breaks the center section and bottom,mrmopartech

 

[Duster346]

Last time I checked Art Carr wasn't a sponsor of this message board. :goodman:

For anyone that doesn't know .. I AM a sponsor here AND we sell racing transmission parts, and torque converters. That includes billet L/R piston kits 62-and up.

All you have to do is call 303.660.0522.

Thanks.