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5.3L Vortec V8 Conversion

Drove the XJ up and down the driveway. Nice to actually have it moving under it's own power again.

Fighting a wiring problem though. Seems my Harnes/PCM combor came from a bastaed child Tahoe. All of the schematics I've seen show a specific wire at a specific location to unlock the torque converter when the brake pedal is pushed (just like an XJ). Problem is, my PCM connector is missing this wire (TCC Brake). I've narrowed it down to having something to do with Cruise Control. I'm pretty sure the donor rig had it, so i've been poring over the applicable drawings. Sent an email to Brendan at www.ls1swap.com . Hopefully he'll have a quick and easy answer for me.
 
Details man Details............How does it run??? I so can't wait for tax return this year cause its 5.3 here I come or maybe even 6.0!!
 
Frank Z said:
I've had it running for a while, runs fine. My excursion today was at a blazing 3-4 mph!!!

Basically checking the t-case and tranny linkage. T-case linkage needs to be tweeked a bit, seems to be binding a little.
Click to expand...

LOL..............haha can't wait to hear how it does at a quite faster more blistering speed :repair:
 
Frank Z said:
All of the schematics I've seen show a specific wire at a specific location to unlock the torque converter when the brake pedal is pushed (just like an XJ). Problem is, my PCM connector is missing this wire (TCC Brake). Sent an email to Brendan at www.ls1swap.com . Hopefully he'll have a quick and easy answer for me.
Click to expand...

Frank,

C1 (blue), pin 33, purple wire. Is there anything in the spot for it? That is really weird, hopefully Brandon will have a answer quick for you. FWIW I have a friend running an LS1 and he told me he never tied this in. I drove mine with it and without it and I did not notice a difference.

But, when you do get it figured out... the Chryco brake switch and the Chevy brake switch do operate differently. The Chevy removes 12vdc from the TCC input at the PCM while the Chryco supplies 12vdc to the TCC input at the PCM. To get mine to work correctly I used a normal lighting relay.

To make the 12v+ when brakes NOT pressed:
12v+ KEY to 30
87a to the PCM Brake Switch Signal
85 to GROUND
86 to the wire going to Brake Lights.

I also installed the relay under the hood and wrapped it a bunch of times with tape so I don't have to listen to it click everytime I hit the brakes.

It functions correctly, but like I said there is not a noticable difference.
 
I did the same thing to mine with a relay, but I honestly have no idea if it is working or not. Part of that is because I haven't driven it very many miles.
 
Nope, nothing in that socket at all. I checked it about 47.5 times cuz I simply refused to believe that it wasn't there.

As far as the OEM stop lamp wiring goes, there are a couple wires that are useable. Everyone open your 97 FSM to page 8W-33-3.

Yellow w/ red stripe from PCM Connector C3, pin C11 to pin 3 on the Stop Lamp Switch and blue w/ red stipe from pin 4 the switch to the Vehicle Speed Control Servo. This is a Normally Closed circuit through the switch. Checked it yesterday with my multimeter.
 
Rather than using a relay, you may be able to use a switch meant for an xj with automatic+cruise, use the switch terminals meant for the TCU to signal the PCM. You may need a pull-up or pull-down resistor (wired from signal line to ground or power depending on how you set it up) but I don't think you will.
 
kastein said:
Rather than using a relay, you may be able to use a switch meant for an xj with automatic+cruise, use the switch terminals meant for the TCU to signal the PCM. You may need a pull-up or pull-down resistor (wired from signal line to ground or power depending on how you set it up) but I don't think you will.
Click to expand...

My switch is meant for an xj with automatic+cruise using the switch terminals meant for the TCU to signal the PCM... the Chryco brake switch works opposite of the Chevy brake switch. The easiest/cheapest way I found to make it work was with a relay as I stated above.

But as I said and fatwreck said, it doesn't seem to make a difference with or without this hooked up.
 
About the gauges... Has anybody thought about running both the XJ and the GM computer and transfer the gauge sending units off of the 4.0 onto the LS engine? Then you could use the XJ computer to run the gauges and the A/C, and let the GM computer run the engine and trans. You could use the 4L60E speed sensor (located in the output housing or adapter plate on the trans) to satisfy the Chevy stuff, and the Jeep speed sensor to tell the speedo how fast the jeep is moving. I don't see why the GM computer needs to know it is in low range, as the shift points are based on the output shaft speed of the trans and engine load anyway. I personally feel that there would be absolutely no issues with this. The tach will require some work, but wont be an issue. Dakota Digital makes a module that can be programmed to convert Tach signals and run whatever gauge you want, and it is adjustable, which means you can run a tach intended for a 6 cyl engine with a V8 and it still be accurate.

Here's a link to the Dakota Digital signal converter:

http://www.dakotadigital.com/index....tegory_id=311/home_id=59/mode=prod/prd127.htm
 
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