I have 89 190E Mercedes-Benz 2.6 L inline 6 cylinder with 157K on it. The car runs at 75 mph with 3500 rpm. My Honda Accord 4 cylinder 2.0L run at 75 mph but only rev at 3000 rpm. Is there something wrong with the Benz tranny or engine?

there are alot of post about this topic...

no your car isnt reving too high, it is just how its geared. Your engine has a good reputation... i like the fact that the car is up around its power peak at crusing speed, it dosen't have to down shift to pass. It all sounds normal.

Your car has a 1:1 fourth gear with a 3.27:1 axle ratio, and the OEM 185/65VR-15 tires are speced at 849 revs/mile.

849 x 3.27 = 2776

These are your revs at 60. At 75 the revs are:

75/60 (2776) = 3470.

My five-speed has the same axle ratio and a 0.80:1 fifth gear so revs at 75 drop to: 0.8 x 3470 = 2776, same as your revs at 60.

The fifth gear yields more relaxed cruising, but due to the torque shy nature of the engine, a down shift to fourth is required for long mountain grades, and from highway speed I downshift to third to pass since the engine doesn't really pull strongly until 5000 revs. In the last ten years, Mercedes and other OEMs have greatly improved torque bandwidth, so modern engines don't feel so soggy on the bottom end. Because of the soggy bottom on the old inline sixes and only four forward speeds on the automatic, D-B geared them rather short for good performance.

The taller top gear on the five-speed manual also improves fuel ecomony. From memory I recall the EPA numbers with the automatic are 18/25 and 18/27 with a five-speed. The quest for better mileage is why many automatics now have five speeds, and six speeds are in work.

Duke

that gearing in 4th means that you will achieve top speed of around 130mph at around 5800rpm, which is right at the power peak of the 2.6li M103.

That and the fact that the car is still drag-limited means that the gearing in 4th is well designed.

You should have no worry though, since the M103 lovs to rev and makes beautiful sounds doing so.