No top gear -300TE - PeachParts Mercedes-Benz Forum

wilsondb · #1 09-07-2003, 12:47 AM

I hope you guys can help me figure out what's up with my '89 300TE. The car is in excellent condition with 195k. Transmission shifts a little crisply on first shift [(1-2?) or (2-3?)] second shift is smooth, no third shift. Just drove 100 miles at 70 mph and blew a half tank of gas. Throttle response was excellent though! Please give me your thoughts as to where to begin isolating the cause of this shiftless experience.

Thank you in advance for your assistance.

KNanthrup · #2 09-07-2003, 12:54 AM

Haha, sorry to laugh but the same thing happened to me when I first bought my car. Did you just recently buy yours?

I can give you an easy answer.

#1) Our cars are factory set to start in 2nd gear, therefore you will only hear a 2-3 and then a 3-4 shift, hence there not being a top gear. This can be over-ridden with a transmission modification, or you can also place the shift lever all the way back into the "2" position at a dead stop and this will lock you into 1st gear.

#2) I believe the rear gearing in your TE is 3.27 rather than (2.73?) or something of the sort, basically the TE's had a higher ratio which in turn gives better throttle response and acceleration, but hurts gas milage.

Anyways I think that answers it accurately although I am no mechanic. If the pros can confirm this then I'd be happy

wilsondb · #3 09-07-2003, 01:07 AM

Thank you, I'm not sure about the starting gear configuration, I have read through many of the postings here on the forum and I do understand that the car may be starting in second gear, but shouldn't I expect better than 12 mpg on the highway at 70 mph? This is my wife's car and I rarely drive it except around town. I have an 85 300TD that I drive about 500 miles a week which I am in tune with on a telepathic level.
I had driven this TE to Cincinnati about a month ago and made the trip up there about 150 miles on less than a half tank at 75-85 mph. I believe the overdrive if there is one has stopped engaging. Maybe I'm mistaken but it seems that the car shouldn't be running at such high rpm's (approx 3200) at 70 mph.

KNanthrup · #4 09-07-2003, 01:19 AM

Well, the RPM's sound right to me because that's what mine turns, but 12mpg certainly isn't right. I went a good 340 miles on a full tank from the george and back doing atleast 80-85 with spirts over 90. I haven't taken my milage in a while but a few months ago it did 19-20 city and something like 27-28 highway. I'd suspect milage will drop significantly when you get above 65 or so due to gearing.

Anyways before I get away too far we will wait for some more guys to reply to this thread, however I am fairly certain that the TE's had the steep gearing and in turn would explain the situation.

One way you can test all 4 gears is so simply do what I mentioned before and stop her and drop her into '2'. Then put it back into 'D' before you take off. Push the throttle about half way so the car can ride out each gear far enough to tell that each gear is there. Simply count the gears... should be 4 in total

wilsondb · #5 09-07-2003, 12:37 PM

Well, I'll take your word for the axle ratio. It would seem that perhaps there is another factor at work in the poor mpg I have observed. Any ideas? The parking brake was not on, the tires are correctly inflated, wasn't carrying a great deal of weight, no strong wind, A/C was set on economy setting. I would have expected the "economy gauge" to have been parked at the far right side if I were getting such poor mileage. I left town with the tank reading straight up .5 tank, when I returned about 105 miles later, the reserve light came on as I exited the interstate.

Air filter has recently been changed, plugs look OK. The car is kind of sluggish though at low speed. It moves along very well on the highway, (sluggishness result of starting in 2nd?)

I know there's something going on. Too great of a change in economy here.

If anyone has an idea where else I might direct my attention I would appreciate your input.

DslBnz · #6 09-07-2003, 01:08 PM

The 300TE has a different rear-axle then the 300E.
The 300E should be 3.07
The 300TE should be 3.46 (same as my 300SE)

Hence, the speed at 80 mph should be;

3500 rpm at 80 mph for the 300E

3850 - 4000 at 80 mph for the 300TE.

Just look at the gearing on your speedometer (the dots). 3rd gear on the TE ends at 90 mph, while the 300E ends at 100.

I think 3200 rpm sounds a little low for the wagon. Should be more like 3400 - 3500.

psfred · #7 09-07-2003, 02:24 PM

As per the other post:

Check your odometer first, then duty cycle/EHA current or CO. It's very possible that you have a fuel problem or bad O2 sensor and you are running very rich (black sooty tailpipe). Fuel distributor failure will result in exessive fuel delivery at all speeds. Expensive fix, alas.

Your rpm is normal.

Peter

wilsondb · #8 09-07-2003, 02:42 PM

Thank you!

The odometer is correct, the trip is the same as I make on a daily basis in anothrer car and the numbers agree with the total distance traveled. It's interstate miles, 51 miles one way.

I don't smell fuel in or around the car while driving or while parked.

I'll search the forum for info on checking the mixture.

Thank you very much!

ke6dcj · #9 12-15-2003, 01:51 PM

Early 300TE's (1988-1989) had a 3.27 diff, at least in the USA.

I confirmed that's what my 1988 300TE has.

:-) neil

MikeTangas · #10 12-15-2003, 02:04 PM

An abrupt drop in fuel mileage usually signifies a bad O2 sensor. May not be bad enough to trigger the O2 MIL, but mileage can drop as low a 10MPG.

DslBnz · #11 12-15-2003, 02:22 PM

I checked the differential in my sister's 300TE the other day(just because), and it was a 3.27 indeed. I don't even know if the gearing ratios are the same. TC lockup must occur at a greater speed than my SE, or perhaps the speedometer is off.

wilsondb · #12 12-15-2003, 02:48 PM

Thank you M Tangas. I have suspected that the O2 may be the culprit after looking at a variety of posts. The car has 200,000 miles on it and I have no idea when (if ever) the previous owner replaced the sensor. The check engine light comes on frequently around town and goes out after a few miles on the interstate which lead me to think it might be the O2 contributing to the poor mileage.

ABS Ligt comes on frequently as well. Sometimes the check engine and ABS lights do an alternating "dance" with a noticeable loss of power while the ABS light is on. Could this factor in as well?

Thanks for your insight.

psfred · #13 12-15-2003, 07:15 PM

Replace the OVP relay and see what happens (behind the splash cover behind the battery). Cost about $70. When it's bad, the voltage gets cut off intermittantly to the fuel mixture control, the ignition, and the cruise control, etc. The relay is there to protect from excessive voltage, but when the contacts go bad or the solder joints go, it goes intermittant. Fuel mixture will go all over the map as the current to the EHA floats all over.

New O2 sensor is probably a good idea too.

Peter