Am I missing a gear? 1988 300 SEL

[philmin8or]

Hellow Group,
Of the millions of questions this site has answered for me I couldn't find this one anywhere. I have an 1988 300SEL when cruising at 65 MPH the engine is running at 3600RPM's this seems high compared to just about any car I drive. If I manually dowshift from 4th to 3rd it will drop down a gear but it still seems like it needs one more gear.
thanks for your help
Phil

[Hit Man X]

Originally Posted by philmin8or

Hellow Group,
Of the millions of questions this site has answered for me I couldn't find this one anywhere. I have an 1988 300SEL when cruising at 65 MPH the engine is running at 3600RPM's this seems high compared to just about any car I drive. If I manually dowshift from 4th to 3rd it will drop down a gear but it still seems like it needs one more gear.
thanks for your help
Phil

That's how it is... the M103 in the W126 is pretty gutless so it has to rev to keep going. Has a 3.47:1 rear diff if I recall.

[johnathan1]

I thought I had lost a gear as well...but it seems like that is normal.

[outofspec]

Funny you should bring this up Phil. I've often thought the same thing in my 1989 300SEL. I'm glad you asked the question, and I'm glad Hit Man had the answer with the tall rear end gears. It seems I learn something new on this site even when I'm not really looking to learn anything.

[johnathan1]

I think the 300SEL has plenty of power for around town driving, but getting on the freeway can be scary sometimes...lol. I think that a 560 rear end would save you a lot of money in gas if you do a lot of highway driving... of course that would be at the cost of some low end power...

[Spelunker]

These cars also start off in second gear, which may mislead those that are counting shifts and suspect one is missing.

Many 4-cylinder cars also rev about 3,500+ RPM on the freeway but they are coarser and much louder.

[Hit Man X]

Big discussion on the 2.88:1 diff swap and a modified valve body for first gear starts. It's in the Perf section.

[86560SEL]

When I test drove a 1988 300SEL a couple of years ago, I never got it on the freeway, but it does not seem like it was turning all that fast, but much faster than the 1995 GMC Suburban I had at the time.

My last Mercedes was a 190D and it revved pretty high over 55mpg (when compared to my Lexus of course). The Mercedes was a 4-cylinder of course.... I never had it over 60 mph, but it was right at 3000 rpms at 60 mph in 4th. If I recall, 2900 rpms to be exact at 60 mph.

3600 rpm at 65 mph seems quite high though, especially when compared to 3000 @ 60 mph on a 190D, which one would think would turn faster than a 300? I am/was considering a purchase of a 1988 300SEL, but if the engine is going to be going that fast on the expressway, I might have to reconsider.

[johnathan1]

Well, I wouldn't let that be the deciding factor in your purchase...the engine turns fast compared to other cars, but the M103 I6 is extremely smooth, and you don't really feel any vibration or noise from it, for the most part. And even with the gearing I had the car over 110MPH several times, and it felt totally solid...

I just sort of decided that it was designed that way, so it should work just fine.

[86560SEL]

Thanks. Well, maybe it will be OK then.

I just still find it strange that a 190D turns 3000 at 60mph, while a 300SE/SEL turns 3600 @ 65mph. I guess the 300 is geared even lower than a 190...

[johnathan1]

Originally Posted by 86560SEL

Thanks. Well, maybe it will be OK then.

I just still find it strange that a 190D turns 3000 at 60mph, while a 300SE/SEL turns 3600 @ 65mph. I guess the 300 is geared even lower than a 190...

Yep, the gearing needs to be super low to move that land-yacht around and still feel somewhat responsive...

[S-Class Guru]

Yes, that's the big issue I always had with my 300SE. The tranny and dif gear is just unsuited to the car. It normally tries to take off in 2nd, but almost can't get itself going; if you push down a bit too much, it bangs down into 1st, which is a "super-stump-puller" and pops your neck.
Then, when you get into 4th, it's screaming along with no overdrive (the actual revs are 3000 at 60, 3500 at 70 - it has a 3.45 rear with 205/65/15 tires).

But, the guys are right, the engine is so smooth and quiet, you never know it's revving it's little guts out - until you see the gas mileage (19-20 on the road).
It's also tough on all the belt-driven accessories, they are also turning really fast.

All that being said, I've had it for 17 years, and it's still a fabulous old car, with no major engine issues. I should have tried to convert it to 1st-gear start, and put in a taller diff years ago, but now it's just too late, we relegated it to the town car - Saturday night special. Still knocks the valet guys out!

DG

[Hit Man X]

Yes, I've never understood the super low rear gearing either. A 300E is only a few hundred pounds less than a 300SE/L and most have a 3.07:1 diff from memory... and 2nd gear start too.

Just can't fathom how putting the car under MORE load to try to get moving from a light, was a good idea for fuel economy.

Ah well, luckily 1st gear starts and 2.88:1 diffs are readily available.

[Hit Man X]

Originally Posted by BENZSTER

Why does everbody slam the poor M103 powered W126 as being such a turd ? I Think my '88 300 SEL is a sports car with the feel of being in a limo. But then my perspective may be a bit different since my other driver is an '81 240d...lol. One thing I've found thats helped on the 300 SEL for myself anyway, was to adjust the transmission bowden cable for a little quicker down shift for in-town driving. Normally if you have to hit the gas in the 2k to 2.5k RMP range (The dead zone) there ain't much happening.

Yes, a 300SEL would be a rocket compared to a 240D. Hell a rickshaw ride in Saigon would probably faster than a 240D to 15mph. Go drive a healthy 300SDL, 420SEL, 500SEL, etc. Huge difference between them and the 300SEL. 40 ft-lbs of torque 1000rpm RPM sooner is why the 420SEL is so much nicer in town plus the econ is so similar between 420SEL and 300SEL (560 is nearly 280 ft-lbs at low RPM like the 420, but the 560 is fairly poor in city econ)... and the 300SDL has it even LOWER. M103 is a fine motor, but belongs in the SE or W124/W201s.

M104/five speed 722 auto would have been GREAT in the late W126 I6 cars.

I drive my 300SEL in 3rd in town up to about 43mph, then I shift into 4th. It's decent once rolling... but load it with a few real sized people, get the AC on, fan clutch locked up, etc. and try to roll out in 2nd gear, and it's just a slug until you get to about 2500rpm in 2nd.

Here's what I'd pick for 126s (for well blended econ/perf):

420SEL/500SEL for all over driving (560 if you don't care about econ)
300SD/L for mainly city


Diesel fuel is just so costly (at least in my region), the cost per mile on the road isn't worth it to me on the freeway. City it is as you'll get considerably higher econ there than with the gas units. I really like having extra high speed power the V8s deliver on the open road for when you have to merge, get around someone, etc. The Diesels and the I6 are just economy versions.

It's up to the owner (and why I HIGHLY advise to drive all variants before buying), but after owning a 300SEL for a long time, it'd be the last W126 I'd recommend/purchase again that was available in the US (Europe had a 260SE! )... I haven't driven a 380SE so can't comment, I'd expect at least the same if not better performance as the TQ peak was only around 2800rpm.