Hi Everyone, I have read many threads here over the years and they have helped me immensely in dealing with many headaches on the ole WJ. Thanks for that!


Ok, Now for the latest issue. I have read countless threads on transmission shifting issues involving the TV cable, Kickdown Cable, Sensors, etc. but don't feel any of these pertain to what I'm seeing (or rather feeling ). When cruising on the HiWay at roughly 65-70MPH It will slam or lunge. Only does it once and a while, Could be downshifting opposed to upshifting. Feels nasty! I cannot reproduce the problem by speeding up or slowing down. I have felt it only once but the wife is noticing it more and more, beginning to concern her, and me! Before I start digging into this to deep I thought I would consult the brain trust here. Any questions please ask. The Trans and motor both have 118k miles. Mostly city miles until recently, my wife has been driving 110+ highway miles round trip to school and home. Thanks All.

 

Check fluid colour & smell - should be a nice cherry red colour, not black/brown and not smell burnt.
Have you ever had the ATF filter & fluid changed ?

 

The color doesn't look the greatest... More brown than red. I had it serviced 14 months ago and had the fluid changed... I wonder if they used ATF4. Would this cause the type of problem I'm experiencing? Ordered a new filter today and will pick up the ATF tomorrow. Ill put a new filter in and change the fluid. thanks for your reply!

 

The problem with doing a drain&fill is you only change 4 qts out of the 8-9 that are in the transmission. The torque converter holds the rest. There is no easy way to do a complete change yourself. I did a multiple change (3 times) with good results. This idea of pouring it down the dipstick while letting it pump out a cooling line is dangerous to the pump if it goes dry in the process. Some business have a machine to do a direct transfer, but the last time I checked, it costs around $150 to do it. Doing a drain&fill 3 times gets the dilution of old fluid down to about 12%. Also, make sure you check the fluid level as printed on the stick; in Neutral, idling, hot.

JMHO.

 

Thanks Dave. Sound like I'll need 20 quarts recommend pulling the filter first?

 

Yes, that will remove the filter as a possible cause of pressure drop. Have you tried driving it with the O/D locked out to see it the problem still appears? 3rd gear is direct 1:1 so the rpm will increase but not dangerously. I think my WJ runs about 2500 rpm at 65 mph in 3rd gear, but I'm just guessing.

There is a thermister (a temperature variable resister) mounted on the bottom of the valve body that monitors trans temp and will kick it out of O/D it the temp get too high. It's covered in fluid unless you're a quart low. You can check it's value when you have the pan off. It should read 1000 ohms @ 70*F plus or minus 10%. This thermistor also doesn't allow it to shift into O/D if the trans fluid is below 32*F.

BTW, my 2000 WJ 4.0 has 190K miles on it with no major problems beside a cracked 0331 head! BUT, that's another story.

 

Great info Dave, thanks a lot. Sounds like a little more ATF but easier and safer than pumping it out of the return line.


Update: Turns out the sucker will hiccup at almost any speed. Someone brought up the Crankshaft Position Sensor (CPS) which is a very common problem. Replaced mine once already but with a cheap 25$ special and not Mopar.... Maybe the problem?

 

It's entirely possible. The CPS is a Hall Effect switch that senses changes in it's magnetic field as the position triggers on the flexplate pass by. Aftermarket sensors tend to be built with poor quality and weak magnetic properties. The Mopar sensor comes with a paper spacer on the end to set it's proper spacing to the flexplate and gets torn off on startup. Aftermarket ones don't have this spacer. When you buy one from a dealer, make sure there is one on it, otherwise ask for a replacement. The sensor is supposed to come with one.