billybalut

Hi all, today my daughter let me know that the transmission in my 1991 corvette was not shifting properly and slipping. If selector was placed in first (1) and (2) no problem, but would slip and then shift in drive or overdrive. I took the car out and it was fine for a half hour drive shifted fine no problems. Then it happened to me, would shift from first to second fine but then started slipping or like it was in neutral and would never shift up. I really know nothing of the 700R transmission, changed the fluid and filter a couple of months ago and it looked fine. The only thing I noticed in this instant problem is that when I check the fluid level the trans fluid looks very clean but has a lot of small bubbles present and the level seems to be up and down when checking it every few minutes while in park. I have read a lot forum input and there is mention of a TV cable adjustment or springs bad in the governor none of which I am familiar with so if any transmission guys can give me the skinny it will be much appreciated. With 90K on the clock I'm having a bad feeling about this problem. Thanks

arbee

Could be more than one reason, but what you describe is common to a burnt 3-4 clutch pack.

jv9999

Likely to be rebuild time. Is the fluid dark and smell kinda burnt?

billybalut

actually the fluid was nice and red with no smell. trans manually shifted easy in first and second and when shifting it up to Drive it would shift but feel like neutral and no pull.

arbee

See post #2

A Peter C4

Time for 4L60 upgrade?

jv9999

Yep, can't diagnose it from here
Hope it's something simple!

Cliff Harris

When the fluid gets hot it loses viscosity and the pressure goes way down. That cause slipping. The only cure is a rebuild.

arbee

He already has a 4L60. 700R4 - 4L60, identical transmissions. As I stated before, it could be several things, but waiting is not going to make it go away. The fluid does not have to look or smell burnt to have a shot 3-4 pack. Things do wear out after 90,000 miles. The style of driving will dictate the degree of slippage. A couple of years ago, I dismantled the trans in an old 89 GMC 1/2 ton with mega miles. The friction material was gone on three plates and several were missing a good portion of their teeth. The fluid looked perfect. However, I had not noticed any slippage as use of this truck was limited, no pulling or heavy loading was involved and no quick accelerations.

A torn lipseal or O ring in the input drum, dislodged 3-4 snapring, input drum 3rd checkball not seating, input shaft faulty Teflon, #7 checkball in the 2-3 accumulator circuit, these are just a few things that would cause this if the clutches aren't burnt. The sure thing though, is if any of these are not corrected, for sure the clutch pack will be history in short order.

A Peter C4

700R--4L60 are simaler but 4L60 has heavy duty parts inside,check rebuild kits,they are interchangeable.Others on forum have said rebuild with 4L60 parts.

arbee

This is incorrect information. A 4l60 does not, by default because of it's name, have "heavy duty parts."

A Peter C4

That's not what I really meant, I have read that 4L60 has improved inner components. I have read somewhere on forum about this. I will talk to my trans guy and ask him about it.

arbee

If you check standard rebuild kits, the same kit is used for 87-93. Same holds true for the ATSG manual. The 4l60 designation did not happen until 1990.

yd328

Just out of curiosity, does most of this require a tear down to test(air/bench)? Can the 2-3 accumulator circuit checkball be done in the car?

Thanks Gary

arbee

Of the things I mention, the 2-3 accumulator checkball is the only one that can be changed with the trans in the car. The valve body would have to be removed but you can get a visual of it by removing the servo.

A Peter C4

arbee sorry 4L60-4L60E are different, correct?

Cliff Harris

The E version is for Electronic. It is controlled by the PCM. You can buy a separate controller. One of the biggest advantages of the E version is that the pressure is controlled by the computer, which has a lot of advantages.

arbee

The internal hardparts, for the most part, are the same between the 4l60 and the 4l60E. The big difference is in the control of the transmission which became electronic. The TV cable was eliminated. Additional sensors were added and different shifting strategies adopted. Internal slippage was able to be sensed and relayed back to the controller. All this in the name of the never ending fuel mileage duel.

Christi@n

Stupid question: did you use the proper fluid? For 4l60 required?

Woodster6

Two years ago my 84 with the 700R4 did the same thing..
3-4 clutch pack was totally destroyed..........Complete rebuild with all new parts, now it is a neck snapper when it shifts. Good Luck