trying to make sure my tranny is not slipping, Is this a good test???

[blau]

Trying to make sure my tyranny is not slipping even a little. Is this good test???

If it is slipping it is not obvious. Drive normay, l shift smooth from what I can tell.

But is this a good test to see if it is slipping.

1. Drive it on the freeway. Take it to a area with a steep hill. So steep if you try to maintain speed by putting more and more gas you call cause the tyranny to down shift automatically.
2. Maintain the same speed by putting more gas (but not enough to cause it to down shift) and if the rpm stay consistent with your speed then you tyranny is not slipping.

In effect what I am doing is putting more load on the tranny to see if the rpm and speed remains consistent (slipping).

Would this be a good test????

[97 SL320]

It would be difficult to gather consistent data without full instrumentation.

The factory method is to hold the brakes on,select drive, push throttle to floor and record the RPM. This is testing torque converter stall speed.

If the RPM is low, the engine does not have enough power.

If the RPM is slightly high ( 200 RPM or so ) , the torque converter stator sprag is slipping.

If the RPM is higher than above, the trans is slipping.

A stall speed test can burn down a slipping clutch but it won't damage an otherwise good transmission.

If the trans is operating smoothly in normal operation is is probably OK. What are your next step in the decision tree if the trans is or isn't slipping? ( What is the end game? )

[blau]

What is the end game? What I am trying to accomplish. Trying to figure out why two (same model same year BMW X5 4.4 sport etc) car drives so differently.

One seem to have more power that the other.

At dead stop one would when press on the moderate gas rev up to 2000 rpm and stay in gear (rpm goes from 2000 to 2200 and I am at 40-50mph) with out pressing more gas and I am more than happy with the acceleration (to the point of being scary).

The other would would rev up to 2000 rpm but would seem at that point if I hold the gas steady it would up shift while the other will stay at 2000 rpm (keep accelerating and becomes scary) at this point if I press more gas the rpm would go up to 2500-2800 before being at 40-50 and no scary feeling.

Again if I am not comparing what should be two identical cars. I would say they both drive normal.

Next steps. Any suggestions from you folks??? The only think I can think of is to change the tranny oil and spark plugs (although don't want to do that because it is not time yet only 28K miles on the clock).

[97 SL320]

What year are these cars? Are the build dates close together? Are the axle ratios / tire sizes the same?

Scan the engine and trans computer to see if the software calibration is the same.

With modern OBD2, a slipping trans could trigger a trouble code so scan the computers for codes.

I'd also look for a sport / normal switch and confirm function.

[Frank Reiner]

Originally Posted by blau

What is the end game? What I am trying to accomplish. Trying to figure out why two (same model same year BMW X5 4.4 sport etc) car drives so differently.

Have you given even the slightest thought to posting to a BMW site?
This is a Mercedes-Benz site.

[97 SL320]

Oooo, you say that with such an elitist flair.

How dare blau sully this list by asking about a car with such poor breeding.

[blau]

I did not get a very conclusive answer. I figure more brains the better. thanks

[Skippy]

So let me get this straight, an X5 with the 4.4 accelerates hard enough at 2200 rpm to scare a 993 owner? I might have to try to get a test drive in one.

Newer autotragic transmissions adapt their shift strategies according to how they've been driven. If the two vehicles have had different drivers for a period of time, the transmissions will tend to act differently, especially under part throttle. It doesn't sound like either one has an actual problem at this point.