auto trans. gearing

[mdchilders]

I have a 91 accord with an auto trans. with "4" gears in it. After taking off onto the highway, the car will go through all 4 gears and will sometimes drop down into a 5th over drive gear?? doesn't do it all the time and have no idea why. Going 70 the tach is almost 3 grand, after the "5th" gear kicks in it drops down to about 2700. Does any one have any idea if this is factory or something aftermarket? Thanks

[jeffcoslacker]

That's the TCC (torque convertor control) lockup occuring. It physically locks the drive and driven sides of the torque convertor turbine together once the car is cruising comfortably, and helps it get better fuel mileage by eliminating the slight slip a turbine always has.

You should feel it unlock and the revs jump back up slightly when you touch the gas or start to go uphill...

A lot of cars you don't even notice it happening, but some are more pronounced that others. 4 cylinders it's usually more obvious.

Most cars have had this since about the late eighties...all have it now that I know of..

[mdchilders]

Hmm. didn't know that. My father also has a 95 dodge ram, with a cummins and it seems to do the same thing. the guy who he bought it off of says its an after market part that was installed and helps get better gas milage. Thanks for the info!

[jeffcoslacker]

200-300 rpm drop is a TCC lockup.

There is no practical way to add additional overdrive gear ranges to street vehicles. Some years of Dodge cummins Ram had a five speed auto with two overdrive ranges, but not '95, I'm pretty sure..