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GDawgC220
01-09-2004, 07:20 AM
Hey all,
I know all MB's have the delayed upshift when you first start driving the car. It holds the gear for longer till the cat(s) are warmed up.

My question is...it usually shifts at 2,000 RPM's in first, then around 3200 RPM's to get out of second.

I take it easy when first going in the morning, or whenever it's been sitting for a few hours, especially in the freezing teen degree's.

Today, I held the RPM's at around 2000 give or take. It went from first to second as normal. Then I just didn't want to push the tranny and engine as it was very cold outside, so I just held it at 2k RPM. After about two minutes, it shifted to third. When I came to a stop sign and started again, it shifted as normal when the cat(s) are warmed up.

Does this do any damage to the upshift module if I just hold it around 2k without letting it shift to 3rd? I use to just go to 3k when starting to drive off to let it go thru the gears, but I wanted to try something different today. Just curious if it's bad or not. Thanks!

-G-

moebiusgold
01-09-2004, 08:16 AM
I don't see that you are doing any damage to the Trans. which is where the upshift delay solenoid is. All you are doing is delaying the warm up slightly. I can't stand reving out my engines when they are cold so I warm them up in the drive way which probably increases the pollution, gas in oil, and warm up time even more than what you did.:( My 99 does the high RPM thing when cold much less aggresivly than my 95.:D

GDawgC220
01-09-2004, 08:19 AM
Originally posted by moebiusgold
I don't see that you are doing any damage to the Trans. which is where the upshift delay solenoid is. All you are doing is delaying the warm up slightly. I can't stand reving out my engines when they are cold so I warm them up in the drive way which probably increases the pollution, gas in oil, and warm up time even more than what you did.:( My 99 does the high RPM thing when cold much less aggresivly than my 95.:D

LOL... I would hope that your 99 doesn't shift as harshly as the upshift delay is work...vacuum tranny vs electronic. Tho, the electronic tranny still has a little jolt to it, but not as noticible as the vacuum ones. :p

But good to know i'm not f'ing anything up, like you, can't stand to watch that RPM needle climb while the engine just woke up.

-G-

GDawgC220
01-09-2004, 08:20 AM
but, what about when the car has been driven, say for about 30 minutes to a store. You go in for about 15-20 min and come back out to leave. You still take it easy or go?

-G-

benzdude
07-03-2004, 11:44 AM
i found some diagnostic info:


the last code I want to talk about is another strictly M-B code. It is the upshift delay codes P1700 and P1701. These codes would only apply to the mechanically controlled automatic transmissions used before 1996. Those transmissions used a throttle pressure cable (control pressure) for determining shift points under various loading. In order to heat the CAT and reduce the cold running time, Mercedes used an electrically controlled, vacuum-operated bellcrank-type lever action to change the capabilities of the control pressure cable. In other words, when cold, vacuum at the switchover valve is switched to a vacuum chamber at the transmission end of the shift cable. There, the actuator movement changes the effective length of the cable. The common problem here is the diaphragm in the actuator element, but testing is simple.

The first test is to see that vacuum is at the switchover valve when running. Next take the line to the transmission from the switchover valve and apply vacuum. In the common failure, the element won't hold vacuum, and you're done with diagnostics.

If the vacuum element holds vacuum, then you must tee into the line at the element and evaluate the vacuum when cold. If there is vacuum at cold running, and a code is present, then evaluate the shift against the criteria. The element is adjustable on the replacements and the cable is always adjustable. A poorly adjusted shift cable adjustment could make the added shift delay not large enough to satisfy the controller.