6.9 idi swap
Thread Starter
|
Trailering
Joined: Aug 2025
Posts: 18
Likes: 1
6.9 idi swap
Currently in the process of swapping my 6.9 idi from a 1984 f250 2wd into a nicer condition 1980 f350 351w 4x4. Things are going smoothish, but I noticed a big difference, the subframes and motor mounts. 351 mounts behind the subframe, with a big hole for the oil filter on the drivers side. 6.9 mounts inside the subframe, right where the hole would be on the 351 subframe.
if anyone has done this project, or something similar, did you fabricate your own mounts? Or would it be easier to take the subframe off the diesel 2wd, swap it into the 350 and get the TTB mounted to that subframe, which looks like it would involve drilling into the subframe for the TTB mounts.
It’s gonna be a big project either way, and I’m prepared for that. Need advice, not judgement.
if anyone has done this project, or something similar, did you fabricate your own mounts? Or would it be easier to take the subframe off the diesel 2wd, swap it into the 350 and get the TTB mounted to that subframe, which looks like it would involve drilling into the subframe for the TTB mounts.
It’s gonna be a big project either way, and I’m prepared for that. Need advice, not judgement.
Moderator
Joined: Jan 2001
Posts: 56,983
Likes: 2,736
From: Virginia
You should be able to take the perches off the 2wd frame and bolt them into the 4x4 frame. Then it should accept the diesel engine. They had at least 3 or more different frame perch configurations to accept all the different kinds of engines that went in these trucks. Carefully eyeball how the perches are mounted in the original diesel 2wd frame, and copy that in the 4x4 frame. I would not be surprised that you find that big hole exists under the 2wd frame perches also once you take them off.
Thread Starter
|
Trailering
Joined: Aug 2025
Posts: 18
Likes: 1
You should be able to take the perches off the 2wd frame and bolt them into the 4x4 frame. Then it should accept the diesel engine. They had at least 3 or more different frame perch configurations to accept all the different kinds of engines that went in these trucks. Carefully eyeball how the perches are mounted in the original diesel 2wd frame, and copy that in the 4x4 frame. I would not be surprised that you find that big hole exists under the 2wd frame perches also once you take them off.
F350 subframe
Diesel drivers side
Diesel passenger side
some of the holes line up, but not all of them.
Thread Starter
|
Trailering
Joined: Aug 2025
Posts: 18
Likes: 1
Yeahhh, that’s the plan. If that oil filter hole interferes then I might just weld in a plate. After a few days of thinking on it I’d rather do that then completely swap the subframes
Thread Starter
|
Trailering
Joined: Aug 2025
Posts: 18
Likes: 1
it only looks like they do on the passenger side, on the driver side I think two of em will line up, I’ll have to drill one and possible weld a plate and drill for the other it’s kinda hard to see in the pictures I posted. This week I’ll be yanking the diesel and comparing perches
Thread
Thread Starter
Forum
Replies
Last Post
70FE250
1967 - 1972 F-100 & Larger F-Series Trucks
3
May 12, 2016 09:43 PM
83shotbed4x4
Small Block V8 (221, 260, 289, 5.0/302, 5.8/351W)
4
Feb 20, 2004 03:05 PM
