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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: DuckAholic1 on August 24, 2013, 11:27:19 pm

Title: 700r4 tranny w/OD not shifting into OD
Post by: DuckAholic1 on August 24, 2013, 11:27:19 pm

I will get straight to it!! My Tranny does not shift into OD!! Well It does, But only when it wants to!
Here's the deal...When getting on hwy it seems to go through all gears ok, approx speeds/shifts are as follows.. 1-2 20mph, 2-3 30mph, 3-4 40mph, OD 60mph??? also, when it does shift into OD, it will downshift back out of OD without any change in throttle pressure, & stay in 4th gear after that.
I tried TV cable adjustment today, Now it shifts very hard, & will not go to OD at all!!
Please forgive me if I sound frustrated, I just am!! Any advice is greatly appreciated!!
OH, By the way, My truck is an 87 C10 w/5.7 350 & 700r4. Thanks again!!! >:(

Title: Re: 700r4 tranny w/OD not shifting into OD
Post by: bd on August 25, 2013, 01:44:27 pm

• Begin by properly Adjusting the TV cable (http://forum.73-87chevytrucks.com/smforum/index.php/topic,7133.msg41219.html#msg41219).
  
  
• What you are referring to as "OD" is actually the Torque Converter Clutch (TCC) engagement.  Overdrive, in fact, is 4^th gear.  TCC should engage in both 3^rd and 4^th gears.  However, TCC will disengage whenever the brake pedal is depressed or if the TCC brake switch is out of adjustment.  TCC engagement/disengagement can be maddening. 
  
  Adjusting the TCC brake switch:
  The "TCC brake switch" (upper image) is mounted adjacent to the "brake light switch" on a stationary bracket located under the dash above the A/C crossover duct on the driver's side.  Assuming you have A/C, remove the A/C duct for access.  A metal tab bolted to the brake pedal arm presses against the TCC and brake light switches to open or close the respective switch contacts.  To help identify the correct switch, the TCC switch connects to two wires: one is pink/black and the other is purple. 
  
  To adjust the switch, physically push the TCC switch toward the tab on the brake pedal arm until the switch bottoms against the tab.  Test drive the vehicle and the TCC should engage in both 3^rd and 4^th gears.  Adjustment is sensitive, so you may need to experiment a little.  Remember, if you depress the brake pedal even slightly while driving, TCC will disengage.  In addition, if you catch under the brake pedal with your toe and "lift" the pedal, the TCC switch can be pulled out of adjustment and you will have to readjust the switch. 
  
  Tip:  If the brake pedal bushings are excessively worn or if the TCC switch is faulty, proper switch adjustment may prove frustrating.
   
  
• In the 1987 model year, the 700R4 had a propensity to downshift from 4th to 3rd gear with modest acceleration and during 'cruise' at highway speed.  The solution is to replace the 3-4 throttle valve sleeve in the transmission valve body (lower image).
  

Title: Re: 700r4 tranny w/OD not shifting into OD
Post by: zieg85 on August 25, 2013, 01:50:45 pm

Excellent write up Rich, great thread to add to the technical pages. 

Title: Re: 700r4 tranny w/OD not shifting into OD
Post by: 454Man on August 25, 2013, 03:23:02 pm

BD where do you get the 3-4  sleeve from?

What's under the hood??? If you have to ask maybe we shouldn't race...

Title: Re: 700r4 tranny w/OD not shifting into OD
Post by: bd on August 25, 2013, 03:55:59 pm

Quote from: 454Man on August 25, 2013, 03:23:02 pm

BD where do you get the 3-4  sleeve from?

Summit, JEGS, et al:

B & M 700R4 Kickdown Kit (http://www.summitracing.com/parts/bmm-70237)

Title: Re: 700r4 tranny w/OD not shifting into OD
Post by: DuckAholic1 on August 25, 2013, 10:50:10 pm

WOW, Thanks bd....That reply was much more than expected!!! Thank you so much!! I will be tinkering in the A.M.  I will be sure and let you all know how it goes. Thanks again!! :o ;D