phishy

I'm pulling P0700 and P0720 along with some other un-related codes. Reset them and they came back. The transmission doesnt seem to be acting weird aside from being a little laggy shifting through gears. TCU going bad? I know the P0720 is for the output shaft speed sensor not matching up with the actual speed but driving it it seems the speedo is correct (or damn close to it).

Sorry I'm not very transmission savvy so any advice or help is much appreciated. Its a 1997 XJ.

SeriousOffroad

Any P07XX code should be addressed by pulling and cleaning the NSS before you do anything else.

phishy

Alright thanks I'll start with that then. Seems pretty straight forward.

CCKen

Actually, the NSS has nothing to do with the transmission Output Speed Sensor circuit.

There's a defect in the OSS circuit wiring or the OSS itself.

A long shot would be a defect in the TCM.

Always check the transmission fluid level (full) and condition before doing anything else.

phishy

I'd say it's safe to assume the trans fluid could use changing. I have checked the level though and it's where it should be.

CCKen

How long has it been since changing it?

Does the fluid appear black-ish on the dipstick?

phishy

Yeah the fluid is looking a little on the burnt side. No idea how long it's been since it's been changed as I just purchased it last week. Judging by the fact that the oil was 3 quarts low and black as hell I'm assuming the PO did absolutely no maint. to it.

CCKen

The very first task in a transmission diagnostic trouble code diagnostic procedure is to check the trans fluid level and condition.

It's time to change the trans fluid.

Use the "drain & Refill" procedure. That is, drain the trans fluid from the oil pan and refill with the amount drained. Do this three or four times untl the fluid appears red-ish. At this point, there's no need to replace the oil screen.

Use DexronIII/Mercon ATF. It may be labled as DEX/MERC, DEXIII/MERC, or other store brand names. As long as the description on the contaner states that it conforms to Dexron III/Mercon requirements it's okay. I use Valvoline DEX/Merc.

Drain the fluid into a container like the one in the below pic so you can get a good idea how much fluid to put back in the transmission. This is a 5 quart container, from Lowes.



To start, get 4 quarts of DEXIII/MERC, the container, and a funnel to direct the fluid in to the container.

After draining & refilling, drive the Heep long enough to shift through the gears, including going into overdrive. You can do this by driving back to the auto parts store to buy 4 more quarts of DEXIII/MERC...LOL...then drain & refill again. Repeat until the fluid drained appears somewhat red. About three-four times. Lot's of money in ATF but it will be worth getting more life out of your transmission.

Always verify the proper fluid level on the dipstick. Don't over service the transmission.

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By the sounds of it (PO's lack of maintenance), perhaps you should drain & refill your transfer case as well. Use DEXIII/MERC. If you are going to do this, and have never done it before, you should get back and get instructions.

Good luck

phishy

Alright cool thanks for the little write-up.

As far as the t-case goes thats a totally different story. The linkage going to the t-case is missing along with the front driveshaft in this thing. No idea how long it's been like that but sorting out the 4wd and getting it working is high on my to-do list. The ultimate question is "why was it disconnected in the first place?". haha

CCKen

The drive shaft was probably removed because the TC Chain is shot and was eating through the TC rear cover (noisy). The chain is driven by the front drive shaft even in 2WD. Why he would disconnect the linkage is beyond me.

See if you can, drain the TC fluid in a clean drain pan and see if the fluid has metal in it.

phishy

Alright I'll give that a go this weekend. Is replacing the TC chain relatively straight forward? Or would I be better off hitting the junkyard and grabbing a used TC.

CCKen

There are tutorials on forums and Youtube vids that show how to replace a chain; however, there may be more issues with your TC than just the chain.

Start looking on Craigslist or maybe the for sale forum here for a replacement TC.

phishy

I might be able to hit up the u pull and pay here. They only charge 60 bucks for TC's. They have like 6 cherokees right now...one of them is bound to have a working NP231 in them.

CCKen

Go for it.

But, take a 10MM hex bit socket and a breaker bar with you to pull the drain plug and see what the fluid looks like. None = NFG, Brown = NFG, Milky = NFG, Dark Red = okay.

Check for up and down play in the front output yoke. Up and down play in the rear output shaft. Both should be tighter than a 14 year old apprentice Nun.

phishy

Alright thanks Will do. So looks like I'm cleaning the NSS, possibly changing the output shaft speed sensor...and possibly replacing the TC. Sounds like an eventful weekend haha.

Edit: and changing tranny fluid.