Conversion questions

[mrpbody]

A couple questions, can anybody tell me if the firewalls are different between the first gens and the 85 trucks?



I am building a 85 Crewcab CTD and I have heard both sides now. Yes, the firewalls are different, and no, they are not different. I read a past post that mention something about it, but didn't go into any detail about it. Does anybody have insight to this question?



On another note, I read some posts about carpet kits for the crew cabs, but their was nothing said about a good source. Has anybody found a good source for the kits yet?

 

[DKarvwnaris]

A couple questions, can anybody tell me if the firewalls are different between the first gens and the 85 trucks?



I am building a 85 Crewcab CTD and I have heard both sides now. Yes, the firewalls are different, and no, they are not different. I read a past post that mention something about it, but didn't go into any detail about it. Does anybody have insight to this question?



On another note, I read some posts about carpet kits for the crew cabs, but their was nothing said about a good source. Has anybody found a good source for the kits yet?

There are minor differences in the early 80's trucks to the 90's CTD's. Which part of it are you concerned about?

Autoworld (406-727-8915)has converted mid 80's crews to CTD's. I can't remember what the differences were, but I know the entire dash will swap Without issue, so it can not be much of an issue. I remember the firewall stamping for brackets being slightly different, but never bothered to record it anywhere, I know we didn't have any problems with the ones we did. The newer harness will bolt right in to the older cab.

 

[bgilbert]

Same 79-93. This conversion has been done many times over. It's known that no firewall mods are needed. Besides cutting a hole for the wiring harness/connection, that is if you're using the wiring from the Cummins donor. I plan on just powering the run/stop solenoid on the injection pump, and just keeping the 85's wiring. I've heard you can use a wire from the distributor for the injection pump. Something that has 12V key on, and run. I have all the wiring from my donor, but at this time, don't plan on using it.

 

[autoworld]

we have a great source for carpet kits!

 

[mrpbody]

I know the dash would swap over and the the wiring harness would work, but I'm more concerned with heater/AC boxes and lines, etc. going through the wall.

Is there any differences between the major componets that attach to or poke through the wall?



I seen a post awhile ago that mentioned the firewall was changed out, but it did not go into reasons why. I don't know what year was being worked on and I have not been able to find the post again.



I have a complete 91 CTD parts truck and I plan on using as much stuff from it as I can. This will be my first conversion so I am just trying to determine if the firewall has to be changed too. Some say yes, some say no. So I thought I would check with you guys here that have (actually) done the conversion yourself.

 

[EarlKann]

How's this.



92 Donor

#ad




And 85 Crew

#ad




There were a few minor differences that I recall. The hole for the throttle cable was in a bit different location. I didn't change out my heater box, but I recall looking at it and thinking that it would probably go in without much hassle. I sure didn't "replace my firewall" don't think I even drilled any new holes in it.

 

[autoworld]

you absolutely do not need to change the firewall, theres lots of room in the 85 compartment - if you need to schmooze it a little, push it out where needed, we are avail for phone advise, just call.

 

[mrpbody]

Thanks for the information, and the pictures. I guess it only pays to listen to those that have done the work. I'll get into once the parts truck arrives from Arizona.



I want to document the swap for another conversion in the future on a 4x4 so I will post pics and comments for you to see.



Autoworld, I will call you for a carpet kit, and EarlKann I may be picking your brain in the next few months for info.



Thanks again.

 

[EarlKann]

No problem.



Good luck with your conversion. We're all here for you!!

 

[HSchroen]

Like everyone said, no firewall swap or mods are necessary beside drilling a hole for the wiring harness (if you plan to swap the entire wiring harness).



I swapped the dash, a/c box, wiring, sound deadener, EVERYTHING attached to the firewall from my '92 donor to my '85 with no problem. Only thing I found was i was left with a few empty screw holes where on the '85 the voltage regulator and those kind of things were bolted to the firewall. Just fill those with sealant so no water seeps in.

 

[CrewCabDiesel]

There are some major differences in the firewalls if you are going to install a manual trans. On the 1989 to 1993 trucks the bulk head connection has been moved over to the left make room for a clutch master cylinder. The clutch/brake petal from a 1989 to 1993 truck will bolt in a 1985 but you will need to make the firewall match your donor. Using your donor as a guide and a little MIG welding it is an simple fix. If you are going automatic it will not be a problem. I would use the newer harness if you have it, makes the install much cleaner and the manifold/fuel heater and wait to start light will work like OEM. All the AC/Heater stuff is a direct bolt in and the duct work is the same from 1981 to 1993. If you want power windows/locks this is the time to install them as well, thier wiring just plugs in the main dash harness.

Kyle

 

[HSchroen]

There are some major differences in the firewalls if you are going to install a manual trans. On the 1989 to 1993 trucks the bulk head connection has been moved over to the left make room for a clutch master cylinder. The clutch/brake petal from a 1989 to 1993 truck will bolt in a 1985 but you will need to make the firewall match your donor. Using your donor as a guide and a little MIG welding it is an simple fix. If you are going automatic it will not be a problem. I would use the newer harness if you have it, makes the install much cleaner and the manifold/fuel heater and wait to start light will work like OEM. All the AC/Heater stuff is a direct bolt in and the duct work is the same from 1981 to 1993. If you want power windows/locks this is the time to install them as well, thier wiring just plugs in the main dash harness.

Kyle

Thanks for the clarification Kyle, I didn't even think about the differences a manual trans would need due to the clutch master cylinder. The auto trans diesels just use a little plastic plug for that hole.

 

[bgilbert]

Here's a members truck with manual trans, doesn't look like he moved the bulk head connector anywhere, just relocated the clutch master cylinder. https://www.turbodieselregister.com/user_gallery/displayimage.php?&photoid=5240&width=0