87 vette, Trans Overdrive
Thread Starter
4th Gear
Joined: Jun 2006
Posts: 4
Likes: 0
87 vette, Trans Overdrive
I recently purchased a 87 vette with an automatic trans. The vehicle has 105,00 miles on it and it runs, and looks very good. I paid $6400 dollars for it. The car shifts gears fine but I can't tell if the car is going into overdrive. I feel it going into fourth gear but the Overdrive light in the dash does not come on. The question is; do I have a three speed with overdrive or a four speed and the fourth gear is actually the overdrive. At 65-70 miles per hour I am turning in the area of 1900 rpm. I have gotten as high as 25 miles per gallon on the freeway.
Can someone explain to me the characteristics of an 87 vette auto trans?
Thanks, Ric in Suisun California
Can someone explain to me the characteristics of an 87 vette auto trans?
Thanks, Ric in Suisun California
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
If you are looking at the "D" in the square box that is just above the digital RPM display, that is only used for the 4+3 manual transmission cars. It lights up when the manual OD unit is engaged. It should not light up at all in the auto trans cars.
The trans is a 700R4 which has four forward speeds with 4th gear serving as the Overdrive gear. With the console gear selection lever in the D position, that allows the overdrive unit to operate and the 1900 RPM you see at those speeds is correct.
The trans is a 700R4 which has four forward speeds with 4th gear serving as the Overdrive gear. With the console gear selection lever in the D position, that allows the overdrive unit to operate and the 1900 RPM you see at those speeds is correct.
Le Mans Master
Joined: Sep 2006
Posts: 6,050
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From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
overdrive
the trans should shift into 4th at about 42-46 mph, and in that range, the converter locks up, giving the sensation of a shift.
to check the torque converter locking, and unlocking, pick a steady speed, say 55, and put your foot lightly on the brake pedal while still keeping your foot on the gas.
your RPM will increase, then remove your foot from the brake, and the RPM's will drop. They should rise about 250-350 RPM, then with foot off the brake, RPM drops to where it was previously.
The brake light switch controls a solenoid called the torque converter clutch (tcc)
to check the torque converter locking, and unlocking, pick a steady speed, say 55, and put your foot lightly on the brake pedal while still keeping your foot on the gas.
your RPM will increase, then remove your foot from the brake, and the RPM's will drop. They should rise about 250-350 RPM, then with foot off the brake, RPM drops to where it was previously.
The brake light switch controls a solenoid called the torque converter clutch (tcc)
Le Mans Master
Joined: Jan 2003
Posts: 5,858
Likes: 7
From: Santa Maria CA
Originally Posted by coupeguy2001
at 1700 RPM, my 86 is going 75MPH AND I get 31.5 mpg
Last edited by 86PACER; Oct 19, 2006 at 03:45 AM.
Le Mans Master
Joined: Jan 2003
Posts: 5,858
Likes: 7
From: Santa Maria CA
Originally Posted by Mundasi
I feel it going into fourth gear but the Overdrive light in the dash does not come on.
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Le Mans Master
Joined: Jan 2003
Posts: 5,858
Likes: 7
From: Santa Maria CA
Originally Posted by coupeguy2001
the trans should shift into 4th at about 42-46 mph, and in that range, the converter locks up, giving the sensation of a shift.
to check the torque converter locking, and unlocking, pick a steady speed, say 55, and put your foot lightly on the brake pedal while still keeping your foot on the gas.
your RPM will increase, then remove your foot from the brake, and the RPM's will drop. They should rise about 250-350 RPM, then with foot off the brake, RPM drops to where it was previously.
The brake light switch controls a solenoid called the torque converter clutch (tcc)
to check the torque converter locking, and unlocking, pick a steady speed, say 55, and put your foot lightly on the brake pedal while still keeping your foot on the gas.
your RPM will increase, then remove your foot from the brake, and the RPM's will drop. They should rise about 250-350 RPM, then with foot off the brake, RPM drops to where it was previously.
The brake light switch controls a solenoid called the torque converter clutch (tcc)
Also, to test that the TCC is working cruise at a steady 40MPH then hammer it. If you feel a chugging or lunching feeling for just a second, it's the TCC engaged. Do it again this time with the brake pedal slighly pressed just enough to light up the brake lights. This time there should be no chugging and just smooth instant acceleration when you hammer it. If not, the TCC/Brake light switch needs adjustment.
Last edited by 86PACER; Oct 19, 2006 at 03:43 AM.
