The vette servo (093) is a great all around upgrade; they run like $12-$15…I install these on all 700r4s and 4l60es I build for a firmer 1/2 shift and overall better clamping/holding power on the band in second gear. What you’re describing is typical of 4l60es in that they all shift soft/sloppy/crappy unless you have a 4l65/4l70 which shift a little bit firmer (and even they can still be improved upon).
Check the fluid for excessive clutch material when you drain the pan. If fluid is overly dark, stinks real bad and lots of burnt clutch material or metal is present, id pull and rebuild it (or have it rebuilt). Otherwise proceed with your service…
Install a shift kit (
transgo SK4l60e). Just follow the instructions that come with it (ignore the directions around modifying the reverse input drum piston, that should never be done). Start with the servo: remove the existing 2nd gear servo (last three digits in casting number are “554” and servo housing. Replace with your corvette servo. Replace all sealing rings and o-rings (all except the fourth gear o ring will come with the corvette servo but you can buy
rubber D-ring sealing rings for the entire servo as well).
Then drop the valve body and 1-2 accumulator housing to install the shift kit. Remove the separator plate, reverse hold down plate and both plate gaskets. Try not to lose any check balls but if you do they’re easily replaceable. The check ball locations will be obvious when you look at the underside of the valve body-i can add a pic if you feel that’s helpful.
After you’re done with the servo assembly, reinstall it and air check to confirm both second and forth apply pistons work - i can provide pics and/or video to show this process if need be…reinstall the servo assembly
before you reinstall the separator plate-to-case gasket so you can air check the second gear apply piston, otherwise you won’t be able to do it. This will validate no sealing rings or o-rings were damaged during reinstallation.
Check your separator plate for excessively worn check ball seating locations. The 1-2 checkball likes to wear into and eventually get stuck in the plate. This causes super late harsh shifts or 1-2 tie ups. I’ll post a picture if you want so you can what I’m referring to. If wear is noted you can either replace the plate with a Transgo plate ($30 or so) or repair yours using a
Fitzall Plate repair kit. Replace the two gaskets on either side of the separator plate - use the white striped set if you have an 01-06 model year vehicle.
Id also install a Sonnax o-ringed oversized boost valve (you can run either the transgo or Sonnax outer pump pressure regulator spring). You will need a small set of snap ring pliers (a reversible set usually runs about $20 or so) to remove and reinstall the snap ring holding in the boost/pressure regulator valve train in the pump.
For fourth gear, replace the existing accumulator piston with a brand new one (couple bucks) as they tend to have wear at the pin bore. You can either run the transgo 4th accumulator spring that comes in the kit or use your old 3/4 acc piston with no seal on it underneath the new one with a seal to effectively block off accumulation - firms up the 3-4 shift nicely. Remove the piston by pulling the pin out with pliers then reinserting it to wiggle the piston out. Alternatively you can run a Sonnax pinless accumulator piston, which is even better.
Check your band clearance by pushing the band forward and rearward while its on the drum - any more than about 1/8 of travel indicates too much clearance and will accelerate band wear. The shift kit comes with a gold colored metal shim that’s installed in between the servo cover and 2nd gear servo piston housing. This will tighten the clearance (if it’s too tight and band binds, grind a little bit of material off the servo apply pin until it no longer binds and driveshaft turns freely).
Lastly, torque all valve body and separator plate-case bolts to 104-108” lbs and install your new filter; reinstall the pan w/magnet - all pan bolts get 98-100” lbs. You will need to go around the pan 2-3 times to fully compress the gasket (don’t use any rubber gaskets that are typically sold at general auto parts stores as they tend to leak).
A Few Common Drivability Symptoms indicating your Transmission needs an overhaul:
1) Transmission slipping (usually during 2-3 shift indicates 3-4 clutch pack is burning)
2) Transmission only shifts when you let off gas pedal (usually presents during 2-3 shift and indicates 3-4 clutch pack is failing/burning)
3) Slipping in 1-2 and 3-4: band is excessively worn at apply points; reverse input drum’s band surface is very warped
4) Delayed engagements/trans “locks up” - gear train failure; pieces of broken gear teeth are wedging themselves between the gears preventing them from meshing
5) No reverse, seconds or fourth gear - sun gear reaction shell has broken
6) No movement in any range setting/gear - pump has failed or input shaft splines have stripped in/at converter
7) vehicle stalls when coming to a stop - torque converter clutch stuck on; usually converter failure
No. If there’s an ECM problem, trans will go into limp mode and have only 3rd and reverse.
