The 1947 - Present Chevrolet & GMC Truck Message Board Network - Scott's 1972 Chevy K-20. A place to start.

The 1947 - Present Chevrolet & GMC Truck Message Board Network (https://67-72chevytrucks.com/vboard/index.php)

- Diesel Conversions (https://67-72chevytrucks.com/vboard/forumdisplay.php?f=240)

- - Scott's 1972 Chevy K-20. A place to start. (https://67-72chevytrucks.com/vboard/showthread.php?t=359010)

Re: Scott's 1972 Chevy K-20. A place to start.

For what it's worth, I'd avoid using the dodge external regulator. They tend to make the lights and charging system surge because the regulater cuts in and out and doesn't keep the voltage steady. The Ford external regulator is the better option IMO.

Re: Scott's 1972 Chevy K-20. A place to start.

Quote:

Originally Posted by Dieselwrencher (Post 6155323)

I'm actually thinking of just using the one in the 72. I can't see any reason why that won't work (and it's only about 5 years old.)

Re: Scott's 1972 Chevy K-20. A place to start.

That's what I'm going to do on mine as well when I get to the wiring portion. I actually installed a ford one on there to get the truck to Good Guys this weekend. But will change back to the GM one when I get my wiring harness un-molested. :lol:

Re: Scott's 1972 Chevy K-20. A place to start.

Quote:

Originally Posted by legendman (Post 6155253)

I found this post a while back, forget where but it might be of some help.
I save it for some reason lol

In the flat 2 wire gm plug one wire will turn on and off with the ign, use this wire to go to the top pin on the dodge regulator, ( the reg has pins in a triangle) hook another wire to this wire on the top pin and run it to either field pin/bolt on the dodge alt. run another wire from the lower right pin on the reg to the other field pin/bolt on the alt. run a ground wire from the reg mount bolt to the alt housing, run the #10 batt wire that went to the alt out put stud on the gm alt, to the dodge out put stud, done! if the alt does not charge, the wire from the gm plug runs thrugh a light bulb in the dash and will not have enough current to power the dodge reg. in that case, run a wire that is switched on and off with the ign (like the wire that runs the IP)to the top pin on the reg and on to the field pin/ bolt on the alt,(some dodge alts have 2 little bolts for the field and some have a small plug with 2 pins for the field circuit) it does not matter witch gets the power from the top pin on the reg, or witch goes to the lower right pin on the reg. hope this helps.

Also check out this thread

http://www.thedieselgarage.com/forum...ad.php?t=58251

Wow, thanks for the additional information Legendman... I didn't see this until today. It was stuck in as the last post on the page. I'll be pouring over the information this evening.

Re: Scott's 1972 Chevy K-20. A place to start.

Wow! That looks sweet!

I noticed it still needs a push rod for the master cylinder, though...

Re: Scott's 1972 Chevy K-20. A place to start.

...don't ever let it be said that I've never posted enough pictures in my build thread...

A bed full of stiff I need to pick through...
https://lh4.googleusercontent.com/-M...o/IMG_0505.JPG

A slightly modified intake manifold (sorry Ryan CO, Randy didn't use the piece you made, but I hope you enjoyed the beer.)
https://lh3.googleusercontent.com/-M...o/IMG_0506.JPG

Modified frame rail, and coolant port.
https://lh4.googleusercontent.com/-7...o/IMG_0507.JPG

All tucked up nicely under the hood.
https://lh6.googleusercontent.com/-k...o/IMG_0509.JPG

Hydro-boost cooler lines:
https://lh3.googleusercontent.com/-S...o/IMG_0511.JPG

https://lh5.googleusercontent.com/-f...o/IMG_0516.jpg https://lh3.googleusercontent.com/-1...o/IMG_0515.jpg

And, finally the punch list that Randy left me that I need to work through...

https://lh5.googleusercontent.com/-e...o/IMG_0517.jpg

Looks like I have a couple of busy weekends ahead of me.

Re: Scott's 1972 Chevy K-20. A place to start.

Quote:

Originally Posted by Mustard72 (Post 6165083)

Wow! That looks sweet!

I noticed it still needs a push rod for the master cylinder, though...

Thanks. Yours is coming along nicely as well. I go check it out every now and again, and like what you've done.

Yes, the master cylinder does need a push rod... neither the hydroboost or the master cylinder came with one, so I've got to source that. There's also a large list that I need to start working through.

Re: Scott's 1972 Chevy K-20. A place to start.

I was just being a smart arse about the push rod.....with the note on the master cylinder and all...

Re: Scott's 1972 Chevy K-20. A place to start.

Excellent!

no worries on the flange, im just glad it didnt fall out of that envelope! haha

Re: Scott's 1972 Chevy K-20. A place to start.

Quote:

Originally Posted by Mustard72 (Post 6165106)

I was just being a smart arse about the push rod.....with the note on the master cylinder and all...

Really?? You'd fit right in with the crew I run with down here. :alc:
Posted via Mobile Device

Re: Scott's 1972 Chevy K-20. A place to start.

Looks very nice Scott! My first bit of advice, chit can the stock CAD unit and get one of the lok right or similar kits. The stock ones are a PITA to keep working right.

Re: Scott's 1972 Chevy K-20. A place to start.

Quote:

Originally Posted by Dieselwrencher (Post 6165415)

Looks very nice Scott! My first bit of advice, chit can the stock CAD unit and get one of the lok right or similar kits. The stock ones are a PITA to keep working right.

Ryan, thanks for the advise. I have looked at dropping that, and I know that there are currently toe broken vacuum lines in the system that I need to contend with. I really want to, but it isnt in the cards at this point in time. Priorities are to get the truck gunning, come up with a fuel tank solution, paint and interior. After that, I'm going to circle back for a couple of things, like winch, cargo rack, new tires, and a couple of other things that are on the list.

They say that projects are never really done, and I'm living proof at this point my goal, similar to you is together to the Goodguys car show in November, with my two buddies ('62 Ranchero &'69 Bronco). We spend a lot of time helpingeachother out, and our goal. Is to get all 3 vehicles done for the show this year.
Posted via Mobile Device

Re: Scott's 1972 Chevy K-20. A place to start.

Scott, you could build your own and save the money. I wish you luck but you have some time. I missed Des Moines Good Guys for three years with my truck before I got it there. I'd really like to get to the Az Good Guys some day.

Re: Scott's 1972 Chevy K-20. A place to start.

Quote:

Originally Posted by Dieselwrencher (Post 6166341)

Yes, there are possibilities. As far as missing shows, well, let's just say that I'm a slow starter as I've had this truck since 1999, and missed a number of opportunities to show it off. I must say though that I've only had it down for one hunting season in 14 years, which is really more important.

Re: Scott's 1972 Chevy K-20. A place to start.

So, since I'm tired of loosing links that I've found in the past, I'm going to start posting reference information here as well. As I have basically put an entire 94 Dodge under my body, I end up having questions that I need to find the answers to. Maybe others will also find the information useful:

Today's topic, Dodge's CAD system. LINK

4WD dodge trucks from 94-early 02’ had a CAD system for the front axle. It messes up a lot so here is a rundown on how to track the problems. One alternative is a posi lock cable that allows you to engage the CAD manually, eliminating a lot of problems. http://www.4x4posi-lok.com/

Vacuum Lines

There are 4 vacuum lines that serve a purpose for the CAD. First off is the white or grey line. This line is the supply line for vacuum. It runs from a T connector on the firewall, down to the vacuum switch located on the top of the of transfer case. Secondly is a green line. This line T’s into the transfer case vent (marked in the pic) and also goes to the vacuum switch to serve as the vacuum vent. It runs up to the firewall and has a fancy end on it that keeps dirt out. Then there are the red and black lines that control the actual CAD. I think red is for 2wd and the black controlled 4wd. They go directly from the vacuum switch to the CAD on the axle. They swap vacuum so one will have vacuum and the other will just be vented.

One cause of issues can be the vacuum lines being full of mud. Blow through each one to make sure they are all clear, any connection can be pulled off, there is nothing that is permanent, if it is rubber, it can be pulled.

http://articles.mopar1973man.com/ima...l/cad/cad1.jpg

Vacuum Switch

The switch itself is very simple and merely swaps vacuum between the red and black lines. All 4 lines go onto the big black connector which will pull off of the vacuum switch. Then you will have just the switch and 4 little ½” tubes where the vacuum lines go. To ensure it is working, take the grey line out and make sure it is getting vacuum (truck must be running). Then pull the red and black lines and the red should have vacuum if it is in 2wd and when you put it in 4wd, the vacuum should switch to the black. You can pull each line out of the 5” or so black hose coming out of the switch so you can feel for vacuum there, just remember where each line went. Make sure the big black connector is not full of mud and you might have to take the vacuum switch out by unscrewing it from the transfer case, then look in it and make sure it doesn’t have mud in the 4 ports either. If it does not switch vacuum, it is junk. NAPA has them in stock as they are a common part among vehicles.

CAD Vacuum Solenoid

The solenoid that does the actual 4wd engaging runs by vacuum with a diaphragm that pushes or pulls the axle coupling to engage or disengage 4wd. You can take it off of the truck and hook the vacuum lines up and see if it moves in and out. It should move in and out easily by hand. If it does not move easily by hand and does not move in and out when you switch vacuum (make sure it actually has vacuum at the lines too), then it is junk and must be replaced. NAPA has those too for much cheaper than anyone else. Ebay has them for even cheaper.

http://articles.mopar1973man.com/ima...l/cad/cad2.jpg

4WD Light Switch (Not being used)

The 4WD indicator light you see on your dash is ran by the switch that is in the CAD housing. When the shift fork moves forward into 4wd, the shaft presses the light switch because it is just a push button. If your light doesn’t work you can test the switch with a multimeter set on ohms. Take the electrical connector off and measure resistance. It should go to 0 (or close to it, maybe 0-10ohms) when it is in 4wd and be at infinity (open) when it is 2wd. You can do it in the truck or you can simply unscrew the switch and just press the button by hand. If it does not do that, it is junk. If I remember, this was a dealer only part. (See video at end)

Shifting Fork

The fork is what moves the coupling back and forth and all I wanted to mention here is that there are 2 versions of it. One is for 94-99’ 2500s, and the other is for 2000-early 2002 2500s. 1500s use the same fork but for different years.

Video

Here is showing how to check for solenoid operation and how to replace a bad one. It shows how to test the 4wd light switch. Also shows how the axle coupler works.

Vacuum Line Schematic

http://articles.mopar1973man.com/ima...d/vac-diag.jpg

Re: Scott's 1972 Chevy K-20. A place to start.

Ok, looking for a little bit of assistance in trying to figure out the O/D for a 47RH transmission. The only diagram I've really found is this:

http://www.transmissioncenter.net/img3.jpg

What I'm trying to determine is the best way to hook up the transmission so that I can continue to have overdrive. It doesn't feel like I'm understanding what they're documenting in sites like
THIS

From reading the components, it seems that I need to install two A/C switches (one for 44 PSI, one for 52 PSI) on the #4 governor pressure port (upper left in this picture)

http://www.transmissioncenter.net/A5...ssure_Taps.jpg

It also provides a warning that "The figures on the pressure switch will only be correct if you have a stock tire size and rear end ratio.", so how does this change if I'm running 35" tires (315/75r16)?

I'm kind of lost on this one, and looking for a little bit of help...

Re: Scott's 1972 Chevy K-20. A place to start.

Quote:

Originally Posted by gerfunken (Post 6175162)

there are more than one ways to hook stuff up. the PATC write up is for a gas engine(thus the use of manifold vacuum) you can just run a toggle for the TCC and OD on the dash and switch them manually when you want either to happen. that would get old.

using the line pressure and a pressure switch is what the PATC write up is about. line pressure in the 47rh is determined by the governor speed therefore your vehicle speed. so a bigger tire will mean you reach 44 mph before you reach 44 psi in line pressure.

you can use the factory dodge ECM and hook it up as it was in the dodge and it will control your shifting in and out of OD as well as the TCC. it will also do your voltage regulation and time out on the grid heaters.

since you dont have a load based source of vacuum, if you eliminate the ECM and use the pressure on the govenor port witch switches, you will have to find a way to switch the TCC off, and OD off when you are under heavy throttle at speed. that would be done i think with the voltage comping out of the TPS, but im not sure how you would set that up. or you can use a micro switch(s) on the throttle linkage somewhere to break the circuit at a certain throttle input so it will kick out of lock up and or OD. im not sure how that would work, as i quit researching after i bailed on the auto.

i am sure Ryan or Nick may have better ideas as they have actually completed this swap before

Ryan

Re: Scott's 1972 Chevy K-20. A place to start.

I am going to use switches for a bit then switch to the dodge ecm down the road
I have a 94 ecm that goes with the 47rh I got.

Here is a pic of the pinout on a 95 ecm.
http://www.4btswaps.com/forum/attach...8&d=1202251104

Re: Scott's 1972 Chevy K-20. A place to start.

Quote:

Originally Posted by ryanroo (Post 6175284)

Ryan, thanks for the reply. Since my speedometer used to be 10% off because of the new tire size, I'm guessing that a 40psi adapter for a 44mph O/D shift. Likewise the 52psi should be about 47psi. I think I understand that now.

Re: Scott's 1972 Chevy K-20. A place to start.

Well, the weekend seems to have come and gone, and I didn't get nearly as much as I wanted to done on the truck. The weather didn't cooperate and we had to call it early due to heat & humidity, and today started off worse so I only took pictures.

The only thing I've done in the engine bay is to pull the old wiring harness from the Chevy. I was planning on getting the Dodge wiring harness off of the engine, but haven't had the chance to do that yet. I also forgot to order the couple of things I needed via the web, so I didn't have any new parts to go put on.

So, no new parts, and the heat and monsoon humidity kept the garage time to a minimum. But we were able to tackle the seats. I've always wanted the 40-20-40 seats instead of the bench and the Dodge provided me the opportunity to use the seats that came out of it. We trimmed about 4" out of the front supports, welded up some brackets, and now new seats.

https://lh4.googleusercontent.com/-s...o/IMG_0529.jpg

https://lh4.googleusercontent.com/-s...o/IMG_0533.JPG

https://lh6.googleusercontent.com/-n...o/IMG_0535.jpg

https://lh5.googleusercontent.com/-A...o/IMG_0537.JPG

https://lh6.googleusercontent.com/-O...o/IMG_0536.jpg