I have an 88 bronco with c6. When truck has set over night or for long periods of time. You put tranny in reverse sit there up to minutes then it drops in same for drive. Start going down road get to stop sign go to take off and it just revs up then drops in to gear. Tranny fluid is full and good and clean. I am wandering if it is the torque converter or the clutches slipping. I figure I will toss this out to you guys and let you weigh in on this. Thanks.

 

anyone have any ideas

 

Check your vacuum modulator first, if thats bad there might be transmission fluid in the vacuum line or the diaphram is just had enough and wont react in the time it should.

 

Sounds like a pump problem. Check line pressures. If it happens in Drive first and reverse, they all use different clutches. The pump and line pressure is common to all 3. Also do a stall test in all gears this will tell you what is slipping. Don

 

Thanks for the help. How do you do a stall test and check line pressure? I would assume you have to have some type of guage to test the pressure right.

 

In an area where you can't hit anything if the brakes won't hold the truck set the park brake. Apply the service brakes and briefly go to Wide open throttle in each gear. If you have a tach record the max RPM the engine will go to. You only have to be at WOT for maybe a count of 3. Let the truck idle in neutral for a while after each test to let the convertor cool. All the RPM's should be about the same. (around 1800 to 2100) Exact RPM is of less importance, they should be similiar. If the RPM is high in D or 1, the fwd. clutch is bad. If it is high in R the reverse/high or low/reverse clutches are bad. Manual 2 (high rpm) is the second gear band or servo. It won't matter much anyway as the trans will have to come apart if any of them are slipping. If the brakes won't hold the truck you need to look after that first.
Line pressure is checked with a gage into the side of the trans. You need some that reads around 0 to 300. It needs a hose so you can see it without been under the truck. The line port is 1/8 NPT. Pressure should be around 80 to 120 psi.
Your best plan if you want to do this is to find a repair manual. This is very basic trans troubleshooting. A good manual will have the correct values, as far as line pressures and stall speeds go. The numbers I gave you are just general rule of thumb numbers. Hope this helps Don

 

Ok thanks Don I will try that. I have a haynes repair manual for c6 trans.