toddk

My C320 Automatic shows 3000 RPM @ 80 mph. It almost feels like it needs another gear. The automatic transmission feels and shifts soft. Is there a shift kit or other mod that will fix this?

VoyagerDude

Your adaptive auto tranny has adjusted to the driver's driving style. You can probably reset it (not sure if disconnecting the battery is the only way) and start driving a bit more aggressively, so the tranny learns that style.

MarkL

Does the adaptive capability change the shift quality (i.e., feel) or just timing of the shifts? Also, no adaptation will change the relationship between rpm and speed at 80 mph, assuming it's in 5th gear.

trench

VoyagerDude's correct about getting more aggressive acceleration. The car has to relearn this pattern. However, if you drive mildly 95% of the time it will be difficult. I think to get around this you could upshift the auto "manually."

Regarding the engine speed at 80mph, the only way to reduce the revs would be to put in a different rear differential - such as dropping the 3.07 diff from a CLK in place of the 3.23 gears that're back there now. This will likely hurt the overall acceleration, though.

- BT

toddk

so does everybody's C320 tach 3000 @ 80 mph

trench

A C320 with the the stock (regular or sport package) 16" wheel/tire combos should tach ~2900 at 80 mph.

- BT

toddk

thank you!

Outland

Sorry...its an automatic...they don't call 'em slushboxes for nothing.

You could change your final drive ratio if you want to turn lower RPM on the highway, but it will slightly hamper accelleration.

BTW, 3k at 80 is actually pretty low already.

jswedberg

Just for your interest, the C32 (with a 3.07 rear end) runs about 2750 at 80 mph. That is really pretty low, unless you are used to big American cars - but even the manual Corvette, with a very long sixth gear, runs something like 2600 at 80 (and has no power available in that gear and speed)

The C320 is supposed to be a smooth car - it will not shift like a racer (or a C32). I think my car (speedtronic) shifts pretty abruptly at times, in fact.

TimmyC230boy

a corvette 4 speed auto with a 2.73 gear will run 2000rpms at 79mph

vadim

German cars are built for autobahn cruising. 80 mph is nothing - they usually do 100-130 mph. That would put the engine to around 4500 rpm.

Smiles

A traditional automatic transmission cannot "adapt" different gear ratios. (This could be true for a continuously variable transission, which the C-Class does not have.) The gear ratios, in each gear and the rear axle, are fixed for any given car unless they are changed.