VenomGT9

New to the XJ, not to forums/DIYs/getting my hands dirty...etc
Looking for guidance on what my next step(s) should be in my diagnosis.
Current symptoms:
- wonky shifting between 4th/OD at highway speeds, usually changes when hitting bumps or any kind of vertical movement
- cruise control does not engage when said wonky shifting occurs, but light DOES go on regardless.
- no CEL, but pulled the following codes via BT OBDII
P0705- trans range sensor circuit malfunction
P0740 - torque converter clutch circuit
P0751 - shift Solenoid A performance
P1718 - multiple
P1742 - multiple
- ABS light is also on but had been on previous to this issue.

So far, I have adjusted the throttle cable and also cleaned the NSS per the DIY instruction but to no avail.
I am mostly mechanically inclined but I'm terrible when it comes to electrical or wiring issues so I'd must rather replace the NSS vs doing some funky wiring work.

Thoughts?

Last transmission service is unknown so that was going to be my next step but wasn't going to do it until I was sure I did or did not need to pull the trans for swapping solenoids.

s346k

does the jeep start in neutral and park? have you unplugged the trans stuff and inspected it? what’s the trans fluid level/condition?

edit: what year and engine etc?

VenomGT9

98 XJ 4.0 4x4
starts in park and neutral, before and after NSS cleaning
unplugged all reachable items pertaining to trans, nothing stuck out as excessively corroded or worn.
trans fluid level is fine, condition is probably half life

cruiser54

I would refresh the connectors in the link below.

http://cruiser54.com/?p=58

And, your brake pedal switch......the one that sends a message to the TCU to unlock the converter when the pedal is depressed.

VenomGT9

connectors cleaned, no joy.

cruiser54

Brake switch?

VenomGT9

Checked the brake connect near the pedal, didn't notice anything out of ordinary.
However, I have noticed a pattern. This morning, wonky shifting the whole ride on the highway even on flat roads. On the ride home (same route), cruise worked the entire way despite many bumps and movements that otherwise have caused shifting. In the morning, I usually let it warm up at least 5min before driving. Today, probably over 10. Point being, fluids very warm before driving started. On the trip home, ambient temp was muchhhhh cooler and did not let it warm for as long just enough to idle speed. Any chance the cooler fluid temp was able to regulate whatever the issue is? In other words, could my trans fluid be getting "too warm" where it no longer is in the range of proper function? (despite Chicago weather lol) I know it needs to reach a certain temp to function but any way it could surpass that?
I should note, my jeep has the oem tow package with a black tub thing on the condenser that Chrysler calls a trans cooler. I have noticed that there is a slow leak where I believe is the lower radiator trans supply line and runs down the lower point near the quick-disco. I purchased a B&M trans kit to fix this issue along with upgrade the lines the rubber hoses.

Thoughts?

cruiser54

I wonder if someone put the wrong fluid in it. Like the Chrysler ATF+4.....

Do a drain and fill with Dex/Merc. Buy a gallon. Just drain the trans using the plug, and refill. Should take about 3.8 quarts.

VenomGT9

I figured that way my only viable step at this point. Any way to tell the difference between the Dex and ATF4 once it's been drained? Assuming no but who knows.

cruiser54

No way to tell. Do one drain and fill first. If there's any improvement, do another couple.

And, keep us informed!!!!

Geek

You can change the selonoid without have to drop the whole trsns. Just dropping the pan you can get to them. But I would check the other stuff first.
mine is a 96 but I had some wires with the insulation worn off. Taped them up. They are down on the left side of the valve cover.

VenomGT9

Well that's good news, thanks.

Drained and filled the pan. Contents were a bit murky so wouldn't call it a waste. I was also able to pry the lower radiator trans supply line off with some pointy bits and a giant flat head, which means I could now replace the stock lines with hose and normal clamps for convenience. Since I could replace the lines, I was able to take out the oem trans cooler and install a B&M product instead.
Wasn't able to road test on the highway but will try this morning to see what the progress was, if any.
For the life of me, I could not get the new hose lines to fit entirely over both lips on the male fitting but was able to get it snug enough past the first and tighten down. Added an in line filter for little added protection.

Will report back with my findings but so far no leaks or issues from the install.

s346k

i would be terribly leary of an in-line filter that small reducing oil flow. how does one monitor it’s contents?

VenomGT9

I thought the same thing with the flow but the filter didn't have too much of a diameter difference than the fittings off the radiator so figured I'd give it a shot. As far as monitoring, I plan to change it each oil change and then go from there as it's fairly simple to swap and easy to reach so I can check as needed with minimal spillage.
For the diagnosis continues. I was able to drive it on the highway without any wonky shifting. Cruise control was engaging and holding steady as it should HOWEVER, it would randomly come out of it (not due to a shift change) as if the brake was being pressed to coast.
Probably unrelated note, coolant temp went passed half way during city driving...no more than normal or worse than gridlock traffic. Is the new trans cooler unit located in such a way to cause the coolant not to be properly cooled? The fan is constantly on so I figured that would be the most logical spot...maybe not?

Thoughts?

s346k

the reduction of oil flow will come from its collection of whatever is in the oil, not its diameter. compare the filter area of that inline filter to that of a normal trans filter. id guess the normal one has 3-4x the filter area and it’s located in an area where the fluid passage is prob 2x the diameter. meaning it will take far less to clog it up the little one with no way to know how much is in it.

that inline filter just sounds like a bad idea with no way to monitor it. you won’t know if it’s a restriction until it blows the line off or kills the trans. just voicing a personal opinion, ‘tis all.

edit - i don’t see your choice of cooler location being an issue. i used a much larger cooler and had no issues with coolant temp.