99 E300 Turbo Diesel 2600 RPMs at 70MPH. Normal?
 

Just picked this up with my son as his first car (and with his own money). First of all, is this a normal RPM for 70 MPH?


Second, I have read these have locking Torque Converter Clutches (722.6 transmission). I don't feel this to be the case because if I hold the speed constant... the RPMs will change slightly (100-200 RPMs) up or down depending on load (uphill, flat, or downhill). I have other vehicles that have a TCC lock up clutch and the RPMs directly correlate to the wheel speed. I will have to give it a little more right foot to keep speed and RPMs constant up a hill... BUT the RPMs and MPH stay constant and related. Is there any explanation for this in the '99 E300TD (other than maybe the 722.6 in this e300td doesn't have a TCC lockup)?

Yes these have a lockup converter.

Low 2000s rpm for 70 mph is what I remember when I had one. 2600 seems high.

Entirely possible the lockup solenoid is not firing when commanded, if you’re seeing fluctuations like that it sure sounds like it’s not locking up.

How’s the fluid? These were originally advertised as ‘sealed for life’ well they realized that’s not so much. Be sure to use the proper fluid, it is not standard ATF. You will need the ‘dipstick tool’, a new cap seal (red tab, don’t skip this or the cap will fall off) and a way to determine fluid temperature (Star diagnosis or an IR thermometer at the pan).

That actually sounds about right, I drive mostly between 80mph and 120mph, and at 80mph it is at almost 3,000RPMs and 5,000RPMs at 120-125mph. Definitly service the trans if it has not been done, Valvoline Max Life ATF and a bottle of LubeGard Red if you like. I plan on going for a drive this afternoon, I will check RPM at 70.

I had a 99 turbo diesel and never understood why Mercedes geared it that way. With all that torque and 5 gears it could cruise along the highway at idle speed.

Especially if considering high speed autobahn driving... I guess faster takeoffs were the priority. But still... there are 5 gears.

I read that 3k rpms is the point where torque converter clutch lockup occurs. That doesn't make much sense to me. It seems like cruising rpms is where you'd want TCC lockup.

Because the gear ratio spread between first and fifth is essentially the same on all 722.6 transmission. they built two families of the 722.6 a high torque and a low torque version. Within those two families they all have the same gear ratios. That's how they got the economy of scale. The only practical way of making fifth taller is by pulling in a taller diff which would make offline acceleration in first gear slower. So you're diff ratio is a compromise between accelerating off the line and your ears bleeding on the freeway. My 97 non-turbo diesel (first year of the 722.6) got an even shorter diff. I don't even bother taking a road trip anymore, it's too noisy. Modern 8, 9 and 10 speed transmission offer a much wider gear ratio spread.

[QUOTE=777funk;4118040]Just picked this up with my son as his first car (and with his own money). First of all, is this a normal RPM for 70 MPH?


There's a full discussion on this topic here: http://www.peachparts.com/shopforum/diesel-discussion/408766-97-e300-d-sale-original-owner-2.html

5th = 2670 rpm at 70 mph is figure I saw in an official looking source, can't remember where.

2.88?

You may have something going on with your exhaust.

I used to do a 80 mile highway trip every day with my 240D with a 3.69 axle and it was alright. Cruised 65mph all day. I think it was around 3.5k rpm. No tach just a big clock:)

3.46

Exhaust is solid.

My bad I forgot that 97 got the overdrive 5 speed I believe 2.88 was for the 722.4 that 96 had

The 606.962 was made for high rpm and speed, this engine lives for 3,000 to 5000 RPMs. Let me see if I can load a few pics from today, dash shots at 70, 80 and 125 mph.

Having problems loading pics, but to answer the question, 26-2700 RPM's at 70. I hit almost 130 at 4800 RPMs, fastest ever. The intercooler loved the 48F air temp. These cars live for 80 -100+. I run 5/40 Redline Euro Series and OptiLube XPD and Boost with every fillup of Cenex Roadmaster diesel. My E300 is a garaged one owner, all records, 5/40 synthetic since 10,000 miles, bought with 147,000, Zero rust, glow plugs done with ceramic paste on the threads and insulator tip. It is an immaculate car and fun to drive.

On an empty road in mexico I assume?:)

This was actually legal in your state ~25 years ago. I think Montana was the only state that had no speed limit on the highway.

I had it maxed out at like 138mph... hwy 5. It gets there fast

I would check that with a GPS. All US market w210s were governed at 130mph except for AMGs and a handful of E430s that left the factory with Z rated tires. The speedometer reads about 5% fast.