98TA6.0

iTrader: (42)

So I installed my rebuilt trans for the second time after a premature 3-4 clutch failure. After installing new clutches verifying the capsule in the case behind the servo was good (I changed cases bc the trans didn't have one for some reason) and triple checking clearances and air checks through the pump, I put the trans back in my truck. Take it down the road and has the exact same issue. Second gear is firm but when going to third it just revs. I haven't had a gauge on it yet. So I put back in the old stock trans that I know for a fact is good bc I pulled it out this morning. Before I installed it I thought I should just throw in the corvette servo, accumulator spring set ups for the one in the case and the removable housing (the double one with a blue and orange spring and the piston in the case with the yellow spring), separator plate (I drilled hole and plugged one hole in accordance with instructions from Pro Built), .500" boost valves, and also the Torlon checkballs. Now this trans was working great before I pulled it out to out the built one in. Swapping these parts brought the issue to this trans so that's good because now I know what the issue can be. But the thing I'm curious about is of the parts listed what could cause third gear issues?

98TA6.0

iTrader: (42)

Just took it down the road and tried to apply fourth with hptuners and acted the same way as third. I know someone is gonna default to the 3-4 clutches burned but this trans has half a mile with this issue. Literally this morning it was shifting just fine and firm.

mrvedit

Since you air tested the input drum in the pump and replaced the 3rd accumulator capsule and/or used a known good case, lets assume those are all good. The only remaining potential trouble areas would be the servo and valve body (VB. The corvette servo has multiple seals to ensure that the 3rd apply fluid cannot leak past it. Last a bad shift valve, dirt within it tiny filters or a sticking valve might be to blame.

Also, are you confident you didn't ruin the teflon seals on the input drum when you made the final assembly? What kind of resizer did you use?

You might also consider an air test plate which bolts in place of the VB and lets you air test all clutches with the trans in the car. Search ebay for "4L60E AIR TEST PLATE"; it costs about $75. If you decide to buy it, I will be happy to buy it from you (a little discount would be nice) after you are done with it.

Sorry to hear you are having so much trouble with this.

98TA6.0

iTrader: (42)

Here's a wierd one for ya. So I swapped back in the valve body plate with the steel checkballs and changed the accumulator housing to the one without the seat. Wierd though when I have the blue spring, piston and orange spring in the newer housing the spring sits flush with the accumulator housing. In the other housing (with the seat) the orange spring comes up about half an inch over the sealing surface. I took it out for a drive and was shocked that it still slipped into third. So in my anger and frustration I decided to execute the trans right there with my right foot. On my way home it went into limp mode which meant third was grabbing well. So I cleared the code and took it out to finish the execution. Right then it decided that it wanted to live and all the gears worked well. This is nuts. Does the trans need a few minutes to "re adapt" to a new valvebody or something?

mrvedit

I asked about your resizer. Some (many) home-rebuilders just use plastic from a bottle and hose clamps to resize the teflon rings. This is fine, but many people tend to overtighten the clamps and size the rings too small. It then takes a few days for the rings to expand on their own and work properly.
Either that or a valve was stuck in the valve body.

This has nothing to do with the 1-2 accumulator. Don't understand your question/statement - with the spring seat out the HD2 blue spring will sit much lower in the housing. With the seat, blue spring, piston and orange spring, that combo will normally be about half an inch over the edge.