1996 Grand Cherokee transmission rebuild & on to other stuff

[Grit dog]

@DoubleDingo Might as well show you what she's doing. At cruise this morning running the headlights, rear defogger, heater and fog lights this is what the gauge was reading.

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That's completely normal, what's not normal is this when I pull up to a stop.

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That's low than normal. In the past it would sit typically just below the 14, like half way between the 14 and the mark below it at idle with a heavy electrical load like this morning.

Hoping to get a change to check it out today.

Looks like alternator to me. Charging well at higher rpms but not at idle.

 

[DoubleDingo]

Mine leaks when cold, not when hot, very odd. Example, we were checking out of the hotel on Sunday, I left it running to check out, and I came out a puddle under the front. We drove to our stop to do one more ruck before leaving. When we stopped, not one drop. All the fluid levels check just fine, but for some reason leaks are there until the engine is hot.

 

[SirRobyn0]

@DoubleDingo & @Grit dog Well I got the new alternator installed this afternoon. Well the noise is gone the last one was making, but still doing the same thing basically. So I tore into the wiring, checked and cleaned every connection I could find, most seemed to make no difference, but cleaning up the body ground helped some. So next I need to find the PCM grounds and clean those up, but most likely looking like a weak AVR in the ECM. I need to drive the Jeep a couple hundred miles early next week, most of it will be in the daytime so at least it won't be long hours with the lights on. If I don't get it nailed down I'll look up the AVR bypass. Basically involves installing a basic external voltage regulator and wiring the alternator to that. I don't think I'd run that as a perinate solution, though guys have been known to do so. I'm running out of time, as an ECM won't get to me by then, but I think I'd like to take my old alternator and enough wire and a regulator to bypass if needed.

 

[SirRobyn0]

As planned, put the wife and dogs into the Jeep and drove down to Battle Ground state park on Sunday, stayed Sunday and Monday nights in a cabin there, got home about 5pm night (Tuesday). I'd compared gauge readings to the readings I was getting on my test equipment at work and the gauge is pretty accurate.

Running down the highway the gauge would never reach 14 volts, instead it would run right around 13 volts. At Idle it would read 12 volts, or even a little lower with high electrical load. Load would not change gauge reading when running down the road but at idle it did.
Then for whatever reason on Monday for a little while it went back to normal readings. Which is pretty much the gauge nailed on 14 volts, all the time, unless running everything at idle where it would drop just under 14 volts (13.8ish), this went on for about 1/2 hour then it went back to the crappy readings. That evening at the cabin I fired up the Jeep, set the brake put a block of wood under the tire put it in drive and tapped on the ECM and the lights brightened up and the gauge read 14V, tap on it again and it goes to not charging well.

This makes sense and lines up with a failing AVR (automatic voltage regulator) which is built into the ECM on these Jeeps. The other thing is when I was initially testing it and got 60amps out of the alternator but could never get it above 13.8 volts even adding a load to the battery with the tester and the engine turn 2,000RPM.

So I took the stuff with me to do an AVR bypass, but did not perform the AVR bypass ahead of time because I reasoned that it was operating well enough to keep the battery up, so the stuff I brought was only to be used in the event of a total AVR failure.

The Jeep did just fine, the transmission worked just like it should and we have no issues from the AVR problem other than me watching the gauge more closely than normal.

I'd put a new ECM in it, but I just dropped a tranny in it, I need to do an evaporator core (I'll do a heat core to while I'm in there), and I have a much larger than expected tax payment soon. So I need to at least put off the ECM.

The bypass in the next post:

 

[SirRobyn0]

The bypass. @DoubleDingo I can't remember if the 1991 has the voltage regulator inside the ECM or not, but if it does this could get you by for a while.

Below picture: what the back of my alternator looks like. The two terminals I circled are the voltage controls. One needs to see battery voltage. The other the voltage regulator controls to vary charge output.

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Below: The external regulator I'll be installing. I just bought a regulator for a 1980 Ram Van with the 360 and a pigtail. Total cost was $30 I think.

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Below: The wiring diagram.

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As you can see it's really pretty simple. The ASD (auto shutdown relay) also feeds key on power to the alternator, so I will grab power off that for the key on power for the regulator. And yes I have already checked the ASD relay and connections so there is no way that is causing my current issue.

So the end result if this works as it should will be a much better functioning charging system, but it will likely not regulate quite as finely as the AVR did. My other concern of course is if the AVR is bad in the ECM how much longer until something more important goes in the ECM?

Probably won't get to this until the weekend, so will let you know how it goes.

 

[SirRobyn0]

Ok I made up as much of the voltage regulator harness at work today as I could. Picture then explanation.

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The black wire, the end circled in yellow has an eyelet soldered and shrink wrapped and will attach to the regulator terminal on the alternator, I'll then route it to the regulator, cut the wire and solder it to the outside terminal on the voltage regulator pigtail.

The white wire with the blue circle has an eyelet soldered and shrink wrapped to it and will be attached to the other regulator terminal on the alternator, the other end will get soldered to the wire on the pigtail that goes to the center terminal on the regulator.

The remaining white wire with the green circle, one end of that wire will get soldered to the pigtail wire that goes to the center terminal. This provides voltage to the regulator so it know what the system voltage is and can adjust the other wire (the control wire) to vary the voltage and also provides 12 volts to the alternator to excite it. When I was making this up I forgot that the 12 volt supply must be switched or the alternator will never turn off, like when the key is off. So I soldered a larger eyelet on the end of it thinking I'd connect it to the positive battery terminal. Since it needs to go somewhere in the relay box instead (likely the ASD relay), I'll need to cut that off and solder it inside the relay box.

The regulator housing needs to be grounded in order to function properly, and if you have ever been under the hood of a 5.2L GC there isn't much metal surface that doesn't already have something attached to it. Traditionally Chrysler liked to mount these things to the firewall, but that's just not going to happen. There is space over by where the air box use to be on the driver side inner fender, but that would require crossing over, running the wires either over the engine or along the core support. While I'm not crazy about mounting it next to the battery it would be well protected there from water, and the wiring would be kept short. So I think I'm going to do that.

My Jeep is old enough that I don't think it'll set a code in the ECM. I'm hoping anyway and if it does I'll just have to live with it until I can afford a ECM for it.

Hoping to get this done tomorrow morning.

 

[SirRobyn0]

Yeah, that's low for sure. Yes, https://www.jeepcables.com/ is the website. Worth a look.

I may not have updated my thread. I quit using the 15w40 about three weeks after switching to it. There was too much piston slap and lifter noise upon startup. I switched to the 5w40 T6 and all of that noise went away.

I read the part where you put the link for the cables, but kind of glossed over the bit about the motor oil. I'm still running the 15W40, and it's treating me fine, but as you know the 5.2 & 4.0 are a bit different. It's kind of funny, on 10W30 or 5W30 my 5.2 will have quite a bit of lifter noise at start up, but on 15W40 it's quiet. Another little odd thing. I switched to the 15W40 mainly to try it, and also because it uses some oil, diesel oil being burned is allegedly easier on the cat. I say that but it's not terrible maybe a quart every 800 miles or so. So the one odd thing I've never been able to add up. I use to have a pinging problem in the Jeep. It would be fine like back and forth to work, but take it on a long trip on the highway and it would ping like crazy (5.2 does not use a knock sensor). Pinging issue stopped after switching. By all of that may not be an effect of the 15W40, but might be because of the heavy duty additives in the diesel oil. I tried running full synthetic in when I first got the Jeep in 2016, but it really wanted to burn a lot of oil with synthetic so that's a no go for me. Kind of interesting to compare notes on oil experiences though.

 

[Grit dog]

So if the manual voltage regulator doesn’t cause a code in the ecm, or even if it does, is that a “permanent fix” so to speak provided the EV don’t have other issues?
I’m with ya on the 15W40. Like Franks Red Hots, I use that sht in everything!
I’m pretty stoked about the 5.2 in the new old rig I just got. Previous oil change sticker was from a couple years ago and within 1000miles of being due. And almost full. I drove it over 500 miles before changing it and it stayed the same!
I’ve seen a lot of small block Chrysler engines go ALOT of miles.

 

[DoubleDingo]

When I got the jeep in 2002 with 88k on the clock, I still had my dad's 79' K15 Sierra Grande and the '65 C20 Mean Green. Both the trucks I ran straight 30w without any issues. I then switched 10w40, also no issues. I then went to 10w30 and stayed with that as that is what the Jeep used. I've tried Castol GTX, Quaker State, and Valvoline in the trucks and Jeep. I stayed with Valvoline for years. In January 2012 I bought my '07 Forester. The PO was a smart guy and ran Rotella T6 5w40 in it, and ran it with 5 quarts instead of the 4.2 that the manual says. He also didn't baby the car. That little car never had any oil consumption problems. I did switch it to Mobil 1 0w40 during the cold months because the 5w40 caused a slow crank on cold mornings. It started fine with the 5w40, but spun faster with the 0w40, and still no oil consumption issues. During the warm months it went back 5w40 T6.

Sold dad's truck to my brother in 2003, wrecked Mean Green on my mom's birthday in 2005 on my way to church. Went without a truck until July 2012 when I got the '81. It used Valvoline 10w30 until this year when I switched it to 5w40 T6. In April 2015 I bought Crusty Biscuit. I thought it was correct on the amount of oil. It was not. I did not know this until returning home from a week-long camping trip in September. I went to change it and there was 8 quarts in the engine! But, the dipstick showed it was on the full mark, and that is because the dipstick that sold it to me had the wrong dipstick tube and dipstick in it. Fortunately it never leaked or burned oil because of this. I did run 15w40 in Crusty Biscuit for a while, but then switched it to Valvoline 10w30 because I was running that in the '81 and the Jeep.

When Crusty is back on the road and the cam has some long heat cycles on it, I might switch to 5w40 T6, but that is big maybe. I was reluctant to switch on the Jeep and the '81, too, because they are flat tappet engines. Both have well-broke-in camshafts though, and the diesel oil has more zinc than regular synthetic does, at least that is what I read when I decided to switch over to T6. The 292 going in Crusty will definitely get either 10w30 Valvoline Racing oil for the first few thousand miles, or regular Valvoline Conventional. Once it is broken I will feel more comfortable using the T6.

I am no oil expert. I do use Purolator PureOne filters on all my vehicles. And I change the oil on a regular basis.

 

[idahovette]

So I think I saw somewhere that Comp Cams has a new hydraulic lifter that needs little or no break in procedure........any body seen this??......or did I dream this up in my poor old pea brain???

 

[SirRobyn0]

@DoubleDingo @Grit dog I think where it comes to motor oil a portion of it is personal taste. I'm unlikely to try the 5W40 since I have nothing running it now. I will admit the 15W40 does slow the starter down a little on my rigs getting at and below freezing. But it's cheap, I'm happy with the oil and I can pour it in everything from my lawn mower, truck and RV. Only my wife's minivan uses something else. It's been on 5W30 full synthetic since it was new.

As far as the manual voltage regulator, yes guys use it as a permanent fix. I know no one that has tried it, I've only read about it on the internet. My plan was to run the manual regulator for 6 months to a year, just to put off the expense for a little bit.

So I spent an 1 1/2 hours wiring it up this morning. I did a really nice job with all the connections soldered, and mounted the voltage regulator really nice where it would be well protected.

Some pictures:

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I even took the time to take the fuse box apart to tap into a key on power supply.

Then I took it for a drive. Unfortunately there is absolutely no way I'm going to tolerate the way this works. Does it charge better? Yes, Yes, it does. However the check engine light is illuminated continuously and the chime keeps going off, and the check gauges light is on and off. It seems to me that the manual voltage regulator is not as closely regulated as the one in the ECM, so not only does the ECM have a problem with it's wires being disconnected but for example, if you run the RPM up, the voltage gauge will get close to where I image is about 15 volts, the chime goes off in the vehicle, the check gauges light comes on and then the voltage regulator brings it down to about 14 volts. I was kind of afraid this might be a problem. Oh well it was worth a shot I suppose and only set me back about $30.

So shortly here I'll be ordering an ECM for the Jeep. Thanks for following along guys this was a fun experiment for me but not going to be staying around. I'll likely leave the regulator mounted and roll up my harness and stick in under the back seat, because this is something that could get a guy home in pinch, it's just the side effects are not tolerable for me.

 

[DoubleDingo]

It must be nice having the alternator up top. Mine is way down low on the passenger side and barely fits through the space to mount it in the bracket. Have to actually loosen the entire assembly to get it mount to the bracket and then tighten it all back up. Videos show the alternator coming out towards the battery with the battery out, but not mine, nope, too much stuff in the way...lol...

 

[Grit dog]

What bout a junkyard ECM? Pretty popular rigs in the scrap yards now I’d think.

 

[SirRobyn0]

It must be nice having the alternator up top. Mine is way down low on the passenger side and barely fits through the space to mount it in the bracket. Have to actually loosen the entire assembly to get it mount to the bracket and then tighten it all back up. Videos show the alternator coming out towards the battery with the battery out, but not mine, nope, too much stuff in the way...lol...

Yea, I know exactly what your talking about. I always took those out the bottom, but was usually on a lift. While the alternator and the A/C compressor are easy to get at the ignition cap and rotor are a massive pain! The 5.2, for it's time anyway was rather tightly fit into the GC's.

What bout a junkyard ECM? Pretty popular rigs in the scrap yards now I’d think.

What junkyards lol. I know you haven't been around the area long enough to remember, but there was time just about ever town had a wrecking yard, Woodinville had 3! Seriously though I know there are still a few around and the shop has an account with LKQ, if I decide to go used I might call them. Nothing like having parts delivered. Frankly though I'm more of the mindset that since I HAVE to replace the ECM now I might as well bite the bullet and a quality reman IF I can find one. Look at how well that's gone with my ESC module on my truck *sigh*.

Probably won't happen until tomorrow but I need to pull the coolant bottle so I can get good access to the ECM which is mounted to the firewall and get the #'s off of it.

I've also heard that some early Chrysler AVR's had a Zener diode that was known to fail. The thing is I don't remember that from back in the day, but if I have the time maybe I'll crack the case on the ECM and see if I see anything obvious. I'm hardly a circuit board repairman but I do have a pair of eyes and can look for the obvious, at least with my glasses on. Will do a little research tonight.

 

[SirRobyn0]

Ok, I'm going to post this info to this thread both to be a quick reference reminder for me in the morning but also maybe someone else will find it useful or interesting at some point. I'm not really sure about that since this is not a Jeep forum but here it goes.

Most people that have the AVR go out report no charging, or intermittent no charging. Few people report that the AVR caused a consistent lower than normal voltage when charging. However there is some stuff I missed when looking the wiring over previously.

#1. Battery temp sensor. My Jeep is kind of on the cusp for having a battery temp sensor and I really didn't pay attention to the tray when I had the battery out, but if memory serves me there is a sensor in the bottom. A bad sensor reporting higher than normal battery temps will not set the check engine light, but will cause the AVR to dial back voltage across the board. This could be what I'm seeing since I'm getting decent amperage, but low voltage. It's something to check.

#2. Drivers side cylinder head by the firewall has a harness ground that the AVR uses. I did not know that.

#3. The red charge wire off the alternator I am 99% certain goes straight to the battery, and but some diagrams show it going to the relay box, then the battery. I need to double check that, if it does go to the relay box then there is a connection there I have not tended to.

#4. Because I did a jump cable test, positive to the charge connection on the alternator, and positive on battery, negative to block and negative on battery, and it still behaved the same. *IF* there is a problem that is not the AVR, then I believe it would have to be on the control side.

Battery temp sensor, man that could be it. When she's cold she charges normal, even underload at idle. Maybe the ECM ignores the battery temp sensor for a few minutes after cold start, or more likely maybe it ignores it until the engine goes into closed loop. Humm. So I just read this.

" If the PCM detects a voltage outside the normal range (0.04 to 4.96 volts) on the battery temp sensor, it triggers a code and the charging rate is set to 14.0 volts as a “safe” option. If the output of the sensor returns to the normal range, the logic module will return to normal operation and it will use the output from the sensor to adjust charging rates." So based on that I should be able to unplug it and see if that solves the charging voltage issue.

Will update tomorrow.