My steep driveway is about 15 degrees and 70ft long. My 223k mile 2005 MDX (usually in D5) would decelerate to a stop somewhere on my driveway. Even if I floor the gas, engine speed doesn't go beyond 2000 rpm. After I rev the engine for some time (less than a minute), A/T TEMP light comes on. The car would still climb after I shift to 1. I think the transmission fails to down shift when climbing a hill, stuck at certain high gear, clutch slips, and ATF temperature goes way up. Other than this, driving on local streets and highways is still normal.

I looked up the Automatic Transmission Symptom Troubleshooting Index in the service manual but couldn't match my problem with a listed symptom. I plan to pull DTCs at O’Reilly tomorrow but doubt I'd get any as D5 didn't blink; MIL (Check Engine) didn't come on.

Any help in diagnosing the problem is appreciated! If a diagnostic tool may help, would you please recommend it?

 

Your clutch packs (for different gears) are probably worn beyond the minimum tolerances.
You need to look into replacing the transmission with a rebuilt one now or it will soon die with melted / welded clutch discs and pads.
A/T TEMP signals a serious problem internally associated with slipping clutches and severe overheating.

 

Thank you for your help, DundukovEM! I guess the end is inevitable. This car has been with me for the last 15 years going through life’s ups and downs. I certainly hope she’s not going down too soon. She’s still driving fine on roads. There’re no codes. The clutch slipping just started to happen recently, maybe once every 15-20 climbs on my steep driveway. Based on the fact that she could still climb when shifted to 1, may I suspect the problem was more like not down shifting in time? I plan to test the 7 solenoids on the transmission and see if any of the oil screens has blockage. Please let me know if there are other places I should investigate.

 

A rebuilt transmission will cost $2.5-3k plus $1k+/- labor to replace it. See if it's worth it or not.