55.2-59 LS PCM Mounting behind the dash on 55-59...pics? Examples?

[daveshilling]

I'm trying to figure out where I can mount the PCM behind the dash, and its a bit cramped in there. I've narrowed it down to a few options:

1. Remove the wiper motor and bits and tuck it up high in that space. I have no wipers, but what am I doing out in the rain anyways?

2. Remove the factory radio and use that space... but the factory radio looks better than the plug, and the new radios that look factory cost $500.

3. Remove the glove box and use that space. They sell a shallow box for A/C installations. I live in the Sacramento area where it reaches 100 degrees often... so I forfeit my ability to run A/C.

4. Remove the glove box, skip the shallox glove box insert, and mount the PCM right at the opening. I get no glove box at all, but maybe I get A/C in the future and I make a storage box behind/under the seat instead.

Option 1 feels like the best move since I don't expect to do much rainy day driving considering how easy it is to break the rears loose when you have LS torque and a light truck, but I do sort of like the idea of having factory bits stay where they are.

What have yall done and how did you like it?

[_Ogre]

imo... option 1 is your worst choice, especially if add ac in the future
imagine having to trouble shoot or replace the pcm

[daveshilling]

Originally Posted by _Ogre

imo... option 1 is your worst choice, especially if add ac in the future
imagine having to trouble shoot or replace the pcm

Thats a great point, it would be WAY in there and annoying. I'm thinking that sacrificing the glove box for now and dealing with it in the future if A/C happens might be a better alternative in the beginning at least, where access to wiring and such is a button press away.

[carbuff382]

I mounted mine behind the seat on the passengers side. Had to get a longer wiring harness but needed to buy one anyway so it worked out well. I'll post a pic tomorrow.

[mongocanfly]

a BP harness should allow you to mount under the seat...a PSI is to short to do it

[daveshilling]

Originally Posted by carbuff382

I mounted mine behind the seat on the passengers side. Had to get a longer wiring harness but needed to buy one anyway so it worked out well. I'll post a pic tomorrow.

Yeah that won't be an option for me. I'm using a reworked factory harness and mounting behind the dash..engine came with the harness so I hopped on ls1tech, followed his Youtube videos, and hoping for the best!

[daveshilling]

Well, I decided to make a home for my LS PCM in the Glove Box area for now.

I don't know if / how long it will stay here, but it will be easy to access while the build is fresh, and once the truck is running, driving, and shaken down, I can perhaps find a more elegant solution.

That being said, the tray is very sturdy for being a single piece of sheet metal, owing to the curved sides giving it strength as well as matching the curves of the opening.
I cut out a section of the rear to make room for wiring to easily reach the PCM.

I welded some nuts to the bottom since you really cant reach in there to hold one. This makes it much easier to install. Lately I've been doing this to many custom fabbed items.




I can grab ahold of the PCM and shake the entire truck, its that solid in there.

[_Ogre]

dang that's a huge pcm, mounted like that sort of defeats the ac install
i was gonna suggest mounting the pcm up to the top
this is how much space you would have with the va compac evaporator
i could have gone with the 1" glove box, just liked the shaved dash look

[daveshilling]

Originally Posted by _Ogre

dang that's a huge pcm, mounted like that sort of defeats the ac install
i was gonna suggest mounting the pcm up to the top
this is how much space you would have with the va compac evaporator
i could have gone with the 1" glove box, just liked the shaved dash look

That's a tight fit but it does look doable! Super helpful to see how much space there is though. The mount I made last night is easily removed since I welded the nuts to it, so basically I'm just kicking the can down the road for now and making it easy-access since it's my first build and first LS.

[Fitz57]

I have reworked harness and went crazy trying to find a spot in cab till I saw Blue57 build. Bought CPP firewall M/C kit. Put alum plate on top and the GM ecm mount on that. I have Dakota Digital dash. 3 screws removed on speedo and plug on back and I’m in. Takes less than 5 min to have ecm out. Don’t think it would work with a speedo cable

[dsraven]

does your build include a set of buckets with a console? couild hide it under the console too if thats the case.
presume there will be no speedo cable since going ls. behind cluster makes sense then, great idea. just as long as the steering column tilts enough to tget the cluster out if required.
could also hinge down from under dash so if engineered right, depending on console/no console, bench seat/no bench seat etc etc. stand it on edge and put a drawer slide on it and hide it behind a nice looking cover panel somewhere. put it behind or under the seat (sliding tray would work) with a plug in style wiring extension, then if you don't like it you unplug it and the extension cord and put it somewhere else.

[_Ogre]

i shorted out my ramjet ecm and had to replace it
it's a little bigger than a pack of cigarettes
the two plugs going into it basically double it