Guys i need help with my 700r4: 1st, 2nd and 3rd gear work fine but when I move the shifter to OD it shifts but it acts like the car is in Neutral.
The TCC is plugged. The car sat 1 year and I remember that back in the day the TCC locked up even in 1st when I drove with the shifter in OD. After a Fluid/Filter change the TCC will not lock up even in 1st anymore but when the 4th engages it acts like it's in neutral and I have to downshift in 3rd. Any idea? The fluid is yellow/ light brown and smells good.The TV cable is adjusted
The car has 122k miles but i think there's a shift kit installed because when it shifts with light throttle it bumps a little and when I tow in Drive it acts like a gear drop.

 

Anyone can help me?

 

I'm no transmission expert, but I'll take a stab at it.

It sounds like the 3-4 shift is happening but it slips in 4th, yes?

The only major thing happening internally when the 3-4 shift happens is the 2-4 band applies and the forward sprag releases.

Since the band comes on in 2nd gear (as well as 4th) and you say 2nd gear is OK, I'm thinking there's something wrong in the 4th apply circuit.

Question 1: Did someone try to install a Corvette servo recently?

Question 2: How is the 2-3 shift? Do you feel any slipping at all in 3rd gear?

Question 3: Has the engine been modified in any way? Particularly where the TV cable attaches to the throttle? Was a carb swapped for the FI system?

Question 4: What do you mean when you say, "The TCC is plugged"?

Question 5: What kind of fluid did you put in after you did a drain/fill/filter change?

 

Thank you for your reply!
1) I am the 5th owner so everything about the trans is unknown.I SUPPOSE there's a shift kit installed because of the harsh 1st/ 2nd shift. I didn't touched the Trans. The servo is the same of the previous owner
2) The 3rd gear pulls good no signs of slipping
3) No it's stock, is a native TPI car
4) I mean the solenoid pigtail of the TCC is plugged into the trans
5) I put Dexron 3 fluid. I only changed the fluid in the pan and replaced the filter with a Delco one with a new O - Ring
When I floor in 3rd the downshift is very good and the 2nd pulls very strong
From a full stop in OD it goes with all the three gears and than the 4th is like neutral

 

I accidentally hit the reverse while going 30mph. The car shut off and after that the OD engages and pulls very good!

 

Sounds like maybe you cleared out some kind of blockage or gunk, interesting. I did that once before too and thought the trans was going to drop, glad the car only stalled instead. Put it in neutral, cranked it up and prayed it would shift and it did, lol. Didn't hurt a thing.

 

So if the 4th engages, does it lock-up? I don't know well how 4th and lock-up work. Could someone explain me if 4th and lock-up are "the same thing" or not?

 

No; definitely 2 different things.

4th is a gear. The same band that works 2nd is applied, at the same time as the forward and 3-4 clutches, which changes the gear.

Here's the range chart for the 4L60E. The 700/4L60 is the same, except of course, the clutches are controlled by hydraulic logic instead of electronic. The power flow is the same however.

3rd gear is 1:1. 4th gear is about .75:1. (can't recall the exact # in that trans)

The lockup is in the torque converter. It is a mechanical clutch that bypasses the fluid coupling; i.e. makes a metallic connection between the engine and the trans input, such that there is zero slippage. It generally applies during 3rd gear, in typical city type driving.

 

ook Thank you for your help!
I noticed the lock-up doesen't engage so I will test it with the ALDL jump
Finger crossed

 

My understanding is if the TCC is working it should lockup:

• In manual 1st (I think)
• In manual 2nd
• In D range in 3rd gear
• In OD range in 3rd (below the speed at which the 3-4 shift occurs)
• In OD range in 4th

The following conditions also need to be met for the TCC to lockup (stock PROM in my ECM):

• Coolant above 50C
• Road speed above 21MPH
• TPS voltage above a certain threshold vs. road speed