Tight TC ?

[D-dog357]

I've got a 92 250le ex-cab. The trans was rebuilt at some time before I bought it and it will idle from a stop - up shift to 2nd and cruise at close to 20mph with out touching the peddle - is that typical/ normal ?

I know these beasts are different then my gassers but I've never had an AT do that before.

[Mark Nixon]

This sounds like a truck a buddy of mine in Iowa used to own.
It had a really tight converter in it and it would almost take off at an idle, you had to know that it would do it, otherwise it'd catch you off guard.

It's not typical, but it's also not a bad thing with the A-518, either.

Mark.

[cmann250]

Mine did that when the idle was set too high. How many threads are showing on the all thread that the throttle lever rests on?

[PToombs]

Any idea what it's idling at? 20mph is a lot at idle, even if the converter is tight.

[dunes450r]

easy way: whats the difference in rpms from neutral to D? if it drops a bunch and starts surging than your idle is too high. since i don't think anyone makes a converter tight enough to do what your saying from an honest 750-800rpm idle, i'd bet your idle is too high, and you have a pretty tight tc, which isn't a bad thing

[D-dog357]

Seems to idle OK, don't have a tach so don't know the number. Put it in gear and it has a very slight nudge. Let off the brakes and it starts to roll nice and easy. After about 5 seconds it up shifts and keeps accelerating albeit slowly till it gets to 17-18 mph and just cruses along. It even will idle at close to 10mph with an empty 16ft car hauler behind it.

Of course this is on level ground or in a parking lot mind you.

I know the trany was rebuilt in so-cal as that was it's original home. It's got a tag riveted to it but to greasy to read. It has a proper external lube sys don't ya know

[PToombs]

I was playing with my '97 on the way to work, and 20 mph is 1200 rpms. I eased the throttle on and off several times to get the feel for it and that's what I came up with. It has a tight converter too. I think your idle is too high. If you look online or check Harbor Freight, you can get a digital tach for about $25.

[Mark Nixon]

Someone on DTR mentioned something about setting the idle according to the way the door mirrors vibrate.
According to this person, a certain amount of vibration equates to the correct RPM at idle.

Mark.

[dantheman300z]

Mine did this up until a couple of days ago. W250 with a518. It was the idle, I had messed with it right after I first got it and it raised the idle. Now I have full travel and lower idle.

[D-dog357]

I'll see if Harbor has one and see what the magic # is.

In all honesty it's not an issue for me. More just curious about it. Actually it's kinda nice going through a parking lot.

THAT'S WHAT IT IS - I've got that rare factory parking lot cruise control

OK - maybe not !

Almost forgot -
I've got 245-85-16's and a 3.56 pumpkin. Got a 3.07 complete too, that would be like double over-drive but not sure if I want to give up towing for mileage.

[DodgeFreak]

Someone on DTR mentioned something about setting the idle according to the way the door mirrors vibrate.
According to this person, a certain amount of vibration equates to the correct RPM at idle.

Mark.

Just stick your finger under the serpentine belt a certain distance and how fast it sucks your finger into the pulley you can determine engine rpm with a little math...might take a finger or two to get it right....lol

[PToombs]

Here's a link for ya. http://www.harborfreight.com/digital-ph ... 66632.html
This is a lot nicer than the one I have too.

[cougar]

Mine rolls away now that I got a new "low stall" TQ in it.

[D-dog357]

OK I went to Harbor and the box says you have to have a clear shot at the mark from less then 18" away. That sounds like I would be feeding my hand to the fan, so I'll have to hold off on that until I install my elec. fans.

On the other hand - I am a tightwad and might just idle down a bit and see what happens and save the $40 for other much needed parts.

BTW, PToombs, thanks for the link !

[PToombs]

No problem! By the way, if you look from underneath, you can get right to it. At our dyno day, I stick the tach pickup right to the oil pan, 80% of the time it stays right there.