Going for a stock'ish rebuild. Found the lower bore scored deep so I bought a super servo for the sleeve. Max pressure I'm going for is 150psi. Any advice on what billet lever to go with. 3.8 might be better with the 16% servo. I'd rather get a 4.2, they are cheaper ha ha. Any other advice on making this bandaid work is welcome. Thanks
47re 16% super servo
- Thread starter 56cummins
- Start date
Big Blue24
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Double up the servo spring so it doesn't bind up when/if it releases slowly. When the 2nd gear servo releases for a 3rd gear shift, the apply fluid pressure on the bottom is still there, the valve body simply directs identical release fluid to the top of the servo so the speed of the release is controlled by the ratio of fluid force area above the servo vs fluid force area below the servo combined with servo spring pressure. With a super servo, you are essentially increasing the apply area on the bottom of the servo with no corresponding increase in the release apply area so you'll need more release spring force to compensate... otherwise you'll have severe 2-3 upshift bind and you'll quickly smoke the 2nd gear band.
A lot of well established, even successful trans builders think the apply pressure on the bottom of the 2nd gear servo goes away on the 2-3 upshift, but in reality it never goes away. Rather, matching pressure is directed to the top of the servo and below the servo cover and the pressure remains for both 3rd and 4th gear. This is why the servo release spring tension in conjunction with 3rd gear clutch clearance, 2nd gear band adjustment, and 2nd gear lever ratio are all important factors to consider to ensure appropriate 2-3 shift overlap timing.
Even if a builder follows the exact same formula each time, there are other "difficult to control factors" within used transmissions that effect shift timing to where two seemingly identical built transmissions can have a flare on one example and a bind-up on the second example.
My best advice is to learn how the system works so you can implement small changes as necessary to correct a flare or bind condition. That's also why most guys do not use a 4.2 or 5.0 ratio lever with a super servo because it's much more prone to bind.
In short, double up the servo release spring with a stock spring and some other aftermarket servo spring that fits inside or outside the stock spring and you'll likely have a good starting point for a 16% servo combined with a higher than stock ratio lever.
A lot of well established, even successful trans builders think the apply pressure on the bottom of the 2nd gear servo goes away on the 2-3 upshift, but in reality it never goes away. Rather, matching pressure is directed to the top of the servo and below the servo cover and the pressure remains for both 3rd and 4th gear. This is why the servo release spring tension in conjunction with 3rd gear clutch clearance, 2nd gear band adjustment, and 2nd gear lever ratio are all important factors to consider to ensure appropriate 2-3 shift overlap timing.
Even if a builder follows the exact same formula each time, there are other "difficult to control factors" within used transmissions that effect shift timing to where two seemingly identical built transmissions can have a flare on one example and a bind-up on the second example.
My best advice is to learn how the system works so you can implement small changes as necessary to correct a flare or bind condition. That's also why most guys do not use a 4.2 or 5.0 ratio lever with a super servo because it's much more prone to bind.
In short, double up the servo release spring with a stock spring and some other aftermarket servo spring that fits inside or outside the stock spring and you'll likely have a good starting point for a 16% servo combined with a higher than stock ratio lever.