4l60E wont go into 4th gear?? any ideas

[Curt_irocz]

Hey guys was wondering if I could get some help. I will post this on LS1 tech also but thought maybe someone here might have an idea. For thoes of you that dont know........
I have a 1995 z28 with a LS1 Swap and the trans is a LS1 style 4l60E. So bascily its a LS1 car.
I bought the ls1 and it came with a t56 harness and ecm. So I pinned all 13 wires into the pcm connectors and ran the oval a4 plug. So at first the car wouldnt shift out of 2nd gear. (because of the t56 pcm) So I had it flashed for a a4 and now it shifts great but wont go into 4th gear. The torque converter will lock up if I have it in Drive (3) or Drive (4) but wont go into 4th gear. If the shifter is in Drive (3) it works normal with engine braking. But Drive (4) when let off the pedal it goes back down to idle with no engine braking.
What could be a probable cause? I thought of the TPS reading backwards, off or have a bad ground but it checks out fine. Could I just have a bad ground else where?
If it makes a difference the torque converter is a 3,500 Precision Industries Vigilante.
Thanks Curt.

[1BADAIR]

is the tcc brake switch wired correctly and the clutch switch bypassed?
does 4th work? car move? you said when you lift it goes to idle

[Curt_irocz]

is the tcc brake switch wired correctly and the clutch switch bypassed?
does 4th work? car move? you said when you lift it goes to idle

Yes car runs and drive like new, it Just wont go into 4th gear (over drive) when your going 50 mph +. I wired the brake switch correctly with 12 volts going threw the switch. When the converter is in lock up while driving i can tap the brake and it will go out of lock up. So I know that is working. The clutch switch is deleted out of the pcm. And I was saying if I let off the throttle while the shifter is set in Drive (4) the engine goes back down to idle with no engine brakeing.

The shifter cable was also properly adjusted.

Hope this makes sence.

[Curt_irocz]

Anyone? We have tried another computer, servos, taken apart the valve body twice, all shift valves move perfect. Accumulator piston looks fine along with all the bores. It CANT be electrical. But We cant seem to figure out what internally would cause this. Again 1st 2nd and 3rd work PERFECT along with lock up.

[hoogiesngrinderz]

Found this in a search

What did you use for the 4th gear servo? Also if you installed a transgo shift kit I would verify that you installed the 3-2 downshift valve spring in the correct location. I have seen guys get confused and install it in the 3-4 relay valve bore and not have 4th gear. I do not think that you have an electrical issue because you have first gear. The same solenoid used for 1st comes on in 4th as well.

[Curt_irocz]

Found this in a search

It DOES have a HD2 trango shift kit. But this trans was in another car and it worked fine. Now its in my car, and its doesnt.

[meissen]

Check the vehicle speed sensor? Does it feel like the shifts are off or like you really have to rev it high to get it to up shift? When we did my LT1 swap there was one wire that was corroded in the wiring harness going to the speed sensor. It caused the trans to go into limp mode and wouldn't shift into 4th gear.

[2002Z4CSS]

Sounds like the intermediate clutch pack is not engaging.

[Curt_irocz]

Check the vehicle speed sensor? Does it feel like the shifts are off or like you really have to rev it high to get it to up shift? When we did my LT1 swap there was one wire that was corroded in the wiring harness going to the speed sensor. It caused the trans to go into limp mode and wouldn't shift into 4th gear.

It shifts perfect. But thats a good thought. Ill check it out. Thanks

Sounds like the intermediate clutch pack is not engaging.

Yeah Im thinking its the 2-4 but I dont get why 2nd works so perfect.

[2002Z4CSS]

It shifts perfect. But thats a good thought. Ill check it out. Thanks




Yeah Im thinking its the 2-4 but I dont get why 2nd works so perfect.

2nd gear used a different clutch pack and to get overdrive usually the intermediate band is applied. That is the weakest clutch pack in the trans.

[meissen]

If it's shifting good then I'd focus on Greg's advice, when my VSS was acting funny I was having to rev it to the moon to get it to shift... it was really noticable. I also didn't have any speed but I don't know if that was from the VSS or the wrong gauge cluster that I had.