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Overdrive Quirk

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Jim_Newman

Jim_Newman

Jedi Hopeful
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Overdrive Quirk

Hello all

I expect that some of you BCFers have had this happen before and know the cause/remedy but after 14 years of driving my "handsome brute", I had a new experience today. (The car is now in Florida where the weather has been great for driving).

I'd travelled about 20 miles at speeds up to 75mph and the overdrive worked, as it always had, perfectly. On the way home as I switched to overdrive, it seemed that it didn't want to shift up. it gradually kind of slid in almost like an old worn out fluid drive automatic transmission. It eventually seemed to get it right and I continued on. As I approached home I began to slow down and, as I reached for the switch to downshift, it shifted down all by itself.

What do you think folks?

As always, your thoughts and advice are appreciated.
 
Re: Overdrive Quirk

Worn accumulator

Worn clutch band

Worn pump

Worn or dirty return/activation valves

Put a pressure guage on it and check your pressure it should be 450 LBS-----Keoke
 
Re: Overdrive Quirk

Bad OD solenoid: When those tiny contacts that activate the strong pull-in coil in the solenoid develop a few ohms of resistance, the unit fails to open the mechanical valve completely. OD engagement is then sluggish. This problem is tricky to figure out, it is often intermittant, and the solenoid works fine the next day.

Check the oil level in your transmission too, low oil can give you similar symptoms.

Bill S
Albuquerque.
 
Re: Overdrive Quirk

I had a similar intermittent problem. Turned out to be the switch on the gear shifter. The switch had virtually no wipe. I was able to lift the rubber boot around the stick and insert a narrow screw driver to manupulate the button on the switch and replicate the problem.
 
Re: Overdrive Quirk

Did you check the oil level in the Trans?
I had similar problems and solved them by cleaning out the accumulator and the ball bearing valves. I also replaced the solenoid. I think a prolonged upshift together with an unexpected downshift while slowing down is more likely to be a pressure problem than an electrical problem.
 
Re: Overdrive Quirk

The problem with troubleshooting OD problems, as Keoke points out, is that many things can cause similar symptoms. Putting a pressure gauge on the unit (there are various threads on the forum about doing this, I have one I might be pursuaded to loan out)will tell you if it is oil pressure. Even knowing that, there are many places the system could be preventing proper pressure build-up. I found a worn ball bearing and pitted seat on the pump pressure relief valve was causing most of my problems, similar to what you are seeing. But hey, they wouldn't call it trouble "shooting" if it were straight forward. It'd be trouble "fixing".
 
Re: Overdrive Quirk

Your car is now in Florida ( warmer temps )....

Drain the o/d + transmission and fill with 60w Valvoline VR1 racing oil.
That will make up for a lot of little internal pressure leaks and restore proper operation even in warmer weather.

I had similar symptoms a few years ago and that is when I started using the 60w Valvoline thanks to advice from Keoke.

It has been working flawlessly ever since.

:driving:

Ed
 
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