700R4 question

[DaveB]

On the way home from the Relic Run I noticed that the 700R4 in the Commando did something a bit weird. If I was going freeway speeds and let it coast down hills the tranny would drop out of overdrive until I gave it gas again. Is that normal for the 700R4 or do I have a problem ? It shifts and runs fine otherwise. any thoughts ?

 

[lhracing]

When you say “drop out of overdrive”, did it down shift to 3[SUP]rd[/SUP] or just coast?

If it coasts in OD that is normal.
If it downshifts to 3[SUP]rd[/SUP] that is not normal.

 

[B2-Bomber]

if it downshifts to third it could be a TV cable issue

 

[mbryson]

I think you're feeling the torque converter lockup or unlock?

 

[DaveB]

When you say “drop out of overdrive”, did it down shift to 3[SUP]rd[/SUP] or just coast?

If it coasts in OD that is normal.
If it downshifts to 3[SUP]rd[/SUP] that is not normal.

When coasting at high speed it acts like it is not engaged and when you go to push on the gas it will rev a bit then engage just fine. I don't think it is dropping to third since the revs aren't that high. Maybe it goes out of torque converter lockup when I let off the gas. I should wire up a light to see what the lock up circuit is doing.

 

[Tacoma]

. I should wire up a light to see what the lock up circuit is doing.

This is a good plan. If I remember, it should be unlocking. I am not near my flow charts though, the factory manual is excellent for flow diagrams in X gear.

 

[lhracing]

When coasting at high speed it acts like it is not engaged and when you go to push on the gas it will rev a bit then engage just fine. I don't think it is dropping to third since the revs aren't that high. Maybe it goes out of torque converter lockup when I let off the gas. I should wire up a light to see what the lock up circuit is doing.

What you are experiencing is the 4th (OD) gear Sprag clutch, not the converter unlocking and this is normal operation for a 700R4. If you pull it down into 3rd gear you will fill some compression slow down but 4th will free-wheel.

 

[DaveB]

OK good to know.