1996 Grand Cherokee transmission rebuild & on to other stuff

[SirRobyn0]

Ok back to my Jeep.

This morning I did the reassembly, but ran out of time to get it fully finished.

So the last thing I needed to do on the box was to replace a few of the gaskets. Specifically I wanted to replace the air inlet to firewall gasket. I just used some camper tape that I had handy. Then reinstalled the box. I cannot tell you how much I hate that part of these kind of jobs. Inevitably it's a pain in the butt to line up and get the studs though the firewall. After getting the box secured to the firewall, I connected the A/C lines, and reinstalled the heater hoses using new hoses of course. Then reassembled inner fender area. A couple of brackets the PCM, and overflow bottle for coolant.

Next was setting the dash back up on the firewall. A part of the job that is easy with 2 people. It's doable alone, but requires walking around the Jeep a few times to get from side to side to get things lined up. After bolt it up, install the center braces, then reconnecting wiring, assemble the VIC center, put the glove box back in, and finally put the steering column back in place and the lower covers.

I ran out of time before getting to pull a vacuum on it, recharge and change the coolant. If I'm lucky I'll get to do it this evening, but in all likely hood it'll be tomorrow morning. I put about 1 1/2 hours into reassembly so I've clocked about 5 hours on the job so far.

Box hung on firewall:

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Dash hung on firewall:

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Will try to get pictures of it fully assembled if I can remember to do so lol.

 

[89Suburban]

Update on the A/C. The system was flat in 2 days. The stop leak did nothing. So I bought a new evaporator and heater core a few weeks ago. I figured if I was going to go though the work to pull the dash to replace the evaporator may as well do the heater core as well. @DoubleDingo I thought you might be interested in my progress so far.

So today was the day to do the tear down. Took about 1 1/2 hours to get the heater box out of the Jeep. Quite a bit quicker than I expected. Honestly if I'd of known that I probably would have replaced it a year or 2 ago when I first started suspecting the evaporator of leaking. My method for the dash was the unbolt and swing method, so I pulled the support bolts for the steering column and dropped it onto the seat, pulled the top plate off the dash by the windshield and unhooked the light sensors. Then unbolt all the bolts that hold the dash to the firewall leaving most of the wiring hooked up. That way a guy can swing the passenger side of the dash up on the seat to make room to work on the heater box without having to fully pull the dash. There is some risk involved with stuff like possibly scratching the center by the shifter and such, but done carefully it's alright.

From there unhook all the wiring to the HVAC box. My Jeep has climate control so there is lots of wiring. Unhook the A/C lines, and the heater hoses, then remove all the bolts that hold the box to the firewall. The worst one and it took me a while to find it, was on the passenger side firewall. A bolt running from the outside into the heater box located UNDER the computer bracket. Totally couldn't see it.

From there pull the HVAC unit out of the vehicle and disassemble all the screw that hold the box together and boy was I in for a surprise. No wonder the evaporator failed! I feel lucky the thing didn't make me sick! And how was it I still had good air flow!

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Disgusting!

So I've got about 3 1/2 hours into it at this point. 1 1/2 hours getting the box out, 1/2 pulling the box apart, and 1/2 putting it back together. The other hour was spent carefully cleaning the entire inside of the box with bleach.

Below: some pic of the Jeep with the dash pulled back.

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That's all the time I have left for today. I have to run the dog to the vet for her annual visit and she'll be ecstatic that she gets to go in the truck even if she has to go to the vet. I have to go to the shop tomorrow to check in, I've taken a couple days of vacation this week but will go in tomorrow so I don't have as much to catch up on next week. Plus I have a very serious meeting with the owners tomorrow but that's another story....

So my plan is to put her all back together on Friday. Then we shall see what happens!

Holy crap.

 

[squaredeal91]

Looks Good! Dash work always sucks!

 

[DoubleDingo]

Holy crap.

That's what I was thinking...lol... I had no idea that big old box was under the dash. I have a better idea of what I am up against when I do mine. I've read it's an 8 hour job.

 

[idahovette]

@DoubleDingo might be worth the drive up to see @SirRobyn0 ???

 

[DoubleDingo]

For sure.

 

[SirRobyn0]

Well I had about 45 minutes before I needed to put the birds away. So I got out my vacuum pump and manifold gauge set.

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For anyone curious that's a Pittsburg vacuum pump. The cheapest unit HF sells. I've had it a few years now and used it probably a dozen times. It has no problem pegging my gauges on -30. That manifold gauge set I bought longer ago. I'm not sure where, I might have come off of one of those discount travelling tool trucks. And if you look in the upper left corner of the picture you can see the front end of my 77' Cadillac.

Anyway I pulled a vacuum on the system let it run for 30 minutes, while I picked up my tools. Setup my bottle of R134A, let some flow into the system for an initial charge. Remember I don't have a scale at home so all I have to gauge fill is pressure and compressor operation. Went to fire up the Jeep. click, click, click..... Battery is too low on charge. So I hooked up the battery charger and went about putting the birds away. So tomorrow I'll have to charge the A/C and see what happens. They are forecasting an 85F day on Monday, so that'll give me to things. If it's still leaking somewhere badly I should know. And if I really misjudge the fill I can suck it and fill it at work on the A/C machine using the scale.

@DoubleDingo & @idahovette DD of course I'd do your heater core and evaporator if you can up, but honestly it's not a hard job. I know it looks daunting, but it's really not, it's not hard at all it's just time consuming. And it'll be a little easier in your Cherokee as there are fewer electronics to deal with. The heater box is not heavy despite the size. I haven't looked up the labor time but I'm up to around 5 1/2 hours.

@squaredeal91 For me it really depends on the vehicle. It had been a LONG time since I've done one of these on a GC of this age and I put it off literally for years, just because I couldn't remember the specifics and I thought I'd be miserable, but other than time, it's been just fine.

So last but not least someone and I can't remember who it was or even for sure the thread, but I think it was what I was doing the intake manifold gaskets on the truck commented that it was only a 1/2 a beer job. If I drank beer I'd give it a 4 or maybe 5. 2 coming out, 2 going back together and 1 more because it wouldn't crank over lol.

 

[SirRobyn0]

Quick update as I'm off to a friends baby's first birthday. Tried to charge it this morning. I apparently have left something electrical disconnected under the dash or broke a wire. I spent an hour and a half chasing it this morning. Looks like I will have to drop the column and pull the dash off the firewall again to get a better look. The symptom is that the heater controller (climate controller) won't turn on or light up.... More tomorrow I guess.

 

[squaredeal91]

I like your air filter setup

 

[SirRobyn0]

I like your air filter setup

Thanks it was cheap. When I bought the Jeep the PO I don't want to say that they didn't take care of it, but it had issues. One of which was the hose from the intake to the air filter box was taped together and the bottom of the filter box was busted up. It was nearly $200 for a hose and box, but that throttle body happens to be a standard carburetor size so I just picked up a $30 edelbrock filter unit. Unfortunately it's got to be small as there isn't a lot of clearance hieghtwise, but it works ok.

 

[SirRobyn0]

Spent 3 hours on the Jeep this morning, pulled the dash back off and tested all the wiring for the heater control unit and found no problems. Got it back together and noticed something. Every time I'd plug the unit in the BCM functions would stop. Power windows, locks, doom lights, dash gauges all stop. Well that pretty much confirmed it right there, the control unit is shorted. Why now, who knows all the movement of the wiring, plugging and unplugging it might have been enough. They are long out of production, so I'll have to see what I can do to find a used unit or have mine rebuilt.... I'll update when I know something.

 

[SirRobyn0]

Update. I ordered a used unit from what appeared to be a good seller on evil-bay. Unfortunately for me he shipped it USPS, so of course it's running late. It's sitting at the post office by the shop, and I won't be back until Monday, so that project is continuing to drag on and on.....

 

[SirRobyn0]

Guess I should give this thread an update. Tracking showed it was at the PO by the shop last Thursday. When I went to pick it up I was told it was still in the trailer and would be unloaded that night. GRRR. That means no heater controller until this week. Well over the weekend I looked at the tracking again and they marked it off as picked up!

So today I drove across town on my lunch to find that they are closed today for Juneteenth. GRRR. If it's there fine. My concern is if it's lost I'm gonna be SOL because they marked the package delivered and picked up!

I'll try again tomorrow I suppose.

 

[SirRobyn0]

Well I went down to the post office for a third time in an attempt to get the package with the controller in it. After waiting in line for 45 minutes, and given the third degree on why I didn't have a pick up slip, and being told over and over again, the tracking shows it's been picked up, it's been picked up! Finally got someone to go in the back and look for it, 30 seconds later I had the package in my hand. At this point I'm just glad it have it. Looks to be in great condition. Now lets hope this fixes it!

 

[SirRobyn0]

Ok, time for un update. @77 K20 since we were talking about this the other day I thought you might want to read the update. I plugged it in Wednesday night. Nothing. The new controller doesn't cause the BCM to turn off, but it doesn't turn on either. checked all the fuses and relays, found no problems and ran out of time.

So this morning I did pinout testing on the wiring harness. It's got 12V where it should, it's got the 5V BCM reference voltage where it should. Check ground. No ground. Ground wire is dead. Run a jumper to the ground and the heater controller lights up, the blend doors start moving but the fan does not kick on. Check the wiring diagram and sure enough the blower motor and the controller share a common ground wire. Check the diagram and they all ground to the same place under the hood. Ground connection under the hood is one of the ones I cleaned up when I was fighting the voltage issue and is still in good shape.

So I pulled the lower cover and glovebox off the passenger side. Sure enough there is a single wire, black connector unplugged. Test the wire and it's the ground. But nothing to plug it into.

At this point I'm out of time again, but I feel good to be moving in a forwardly direction. I don't feel bad about getting the controller, my old unit was throwing an error occasionally, but still worked, and obviously has a larger issue if it'll kill the BCM at times. So I don't feel bad about getting the new one and will run the new one. I just hope that I did not capture the wire I need behind the heater box. That would require pulling the dash again and I'd really like to move on to other projects, but at least I know what the problem is now, and that finding that wire will be the solve.