Rpm Question
 

Hi, I have a 1987 300E. I noticed that while on the freeway that the rpm's at 65 mph is about at 3000 and 70 mph is at 3100 this seems kind of high to me. anyone know what it should be? My Honda used to be at 2800 rpm at 65mph.
If it is high what could be the problem? Thank you.

That doesn't sound high to me. Drivelines attached to the m103 are usually geared that way. It may take some getting used to, but as long as you do your routine maintenance you'll be fine.

If you want fewer revs on the freeway you'll need to either swap the diff or the trans.

Axle ratio times tire revs per mile = revs at 60 (for a 1:1 top gear).

3.07 x 837 = 2570

Actuals may vary slightly due to tire revs per mile tolerance within the size group, tire wear, and converter slippage.

Revs at any other speed can be determined by linear proportioning.

70/60(2570) = 2998

Installing different revs/mile tires will not affect the RPM-speed relationship - just speedometer accuracy.

The early 300Es were performance sedans - quite quick for sedans in the mid-eighties. The engine has high specific output, but is somewhat torque shy, so they geared them fairly short, however, they will still pull close to 140@6000.

Sometime later the standard axle ratio was changed to 2.87, and they got heavier. The early 300Es are genuine hot rods.

260Es and all US 190Es including the 2.6 and 16V got 3.27:1 axles.

Duke

[QUOTE=benzman2] I noticed that while on the freeway that the rpm's at 65 mph is about at 3000 and 70 mph is at 3100 this seems kind of high to me.

I'll trade you for your 70mph rpms.

The 126 car with the small motor(same as yours) turns 3400 rpm at 70mph.

You can't compare this setup to what you may be used to seeing on Asian makes.