disc conversion
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Freshman User
Joined: Oct 2006
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From: North Dakota
disc conversion
Hello folks,
I have a 1974 F-100 4X4, I also have 1978 F-150 4X4. I was thinking I could take the whole front axle out of the 78 w/ disc brakes and replace the one under the 74 that has drums. I was thinking this should be a pretty straightforward swap. Do I need to use the mastercylinder and prop valve from the 78 as well? yes, i have taken into account gear ratios.
I have a 1974 F-100 4X4, I also have 1978 F-150 4X4. I was thinking I could take the whole front axle out of the 78 w/ disc brakes and replace the one under the 74 that has drums. I was thinking this should be a pretty straightforward swap. Do I need to use the mastercylinder and prop valve from the 78 as well? yes, i have taken into account gear ratios.
Fleet Mechanic
Joined: Oct 2003
Posts: 1,371
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From: Green Springs, OH
Pretty sure you should be able to do that without much trouble just check your frame widths and mounting points good. You will need the vacuum booster, master cylinder w/ pushrod, and the proportioning valve from the old the 78. I take it the 74 is in better shape than the 78 just wondering why you would want to swap the axles.
I'll have the Roast Duck
Joined: Jul 2002
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From: Northshore, MN
The idea is that the disc brakes require a different fluid amount than drums, so the 78's prop. valve, and master cylinder are needed. But like mil1ion said, the boosters may be different between those 2 years, so a little trial and error may be in order. The crucial part is the correct pushrod length, too long and you'll be brake dragging, too short, and you'll have not enough brakes, so make sure everything is right. This has been posted several time, maybe try a forum search?
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Freshman User
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From: North Dakota
yeah, i figured the prop valve woulb be needed. i guess i thought that since the bodies were almost exactly the same the booster would work....guess i can always drill mounting holes, i'll have to check on that rod tho.
and as far as why: the 74 is manual tranny, the 78 was auto (I despise autos), but i picked up the 78 for $300, it ran, the rear driveshaft was shattered, so i figured i would use the 351M in place of the 360 (already have the right flywheel and bellhousing), switch the dana 21 out with the np205, and use the front for the discs. the interior of the 78 was completely trashed, hood was about as stiff as water. amazing that the motor ran great even tho the distributor and wiring was melted due to an engine fire lol
and as far as why: the 74 is manual tranny, the 78 was auto (I despise autos), but i picked up the 78 for $300, it ran, the rear driveshaft was shattered, so i figured i would use the 351M in place of the 360 (already have the right flywheel and bellhousing), switch the dana 21 out with the np205, and use the front for the discs. the interior of the 78 was completely trashed, hood was about as stiff as water. amazing that the motor ran great even tho the distributor and wiring was melted due to an engine fire lol
I'll have the Roast Duck
Joined: Jul 2002
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From: Northshore, MN
a swap from a 360 to 351M will require the 78's motor towers too. Just to let ya know.
Also, the 205 will not just bolt up where the dana 21 was. The 435's output shafts are different. Bottom of my gallery shows why.
Also, the 205 will not just bolt up where the dana 21 was. The 435's output shafts are different. Bottom of my gallery shows why.
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Freshman User
Joined: Oct 2006
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From: North Dakota
yeah, i got a whole new (well, new to me) tranny for that. and i was told of the mount towers, at least i still have the rolling 78 chassis for that stuff. was the dana 21 considered a strong case in it's day? cuz i managed to tear a 1"x3" hole in the case
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I'll have the Roast Duck
Joined: Jul 2002
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From: Northshore, MN
IMO, it was too small for stock trucks, let alone built ones. 205 will be a significant upgrade.
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From: In the Middle
Will the '78 towers work on the '74 frame?
Check your frame to be sure the towers will work. I just swapped a 360 into my '79 Bronco frame that had a 351M and the towers had to be welded to the frame because the bolt holes didn't line up.
Here are a couple pics - one compares the two towers, with the FE tower being the smaller of the two. The other shows the FE tower on the '79 Bronco frame. The blue arrow is the bolt hole in the frame that doesn't line up with the FE tower. The yellow arrow is the hole in the FE tower that doesn't line up with the hole in the frame. The red arrow points the rear bolt that went through the 351M tower that also doesn't work with the FE tower. This bolt also goes through the shock upper mount bracket.
http://i44.photobucket.com/albums/f2...9-09-06021.jpg
http://i44.photobucket.com/albums/f2...8-12-06021.jpg
.
Check your frame to be sure the towers will work. I just swapped a 360 into my '79 Bronco frame that had a 351M and the towers had to be welded to the frame because the bolt holes didn't line up.
Here are a couple pics - one compares the two towers, with the FE tower being the smaller of the two. The other shows the FE tower on the '79 Bronco frame. The blue arrow is the bolt hole in the frame that doesn't line up with the FE tower. The yellow arrow is the hole in the FE tower that doesn't line up with the hole in the frame. The red arrow points the rear bolt that went through the 351M tower that also doesn't work with the FE tower. This bolt also goes through the shock upper mount bracket.
http://i44.photobucket.com/albums/f2...9-09-06021.jpg
http://i44.photobucket.com/albums/f2...8-12-06021.jpg
.
I'll have the Roast Duck
Joined: Jul 2002
Posts: 9,622
Likes: 108
From: Northshore, MN
actually they may need welding just like yours(460's), just vise versa. The fact is using the FE mounts in place with a 351M puts the engine 1" off. So did your FE bronco fit everything ok with the front bolt hole as your point of reference? (Trying not to hijack, here)
I used 300 6 towers in my 79 bronco, But they bolted in ok. If I remember, they didn't line up with the v8 bolt holes, but it's been so long, I can't remember for sure.
I used 300 6 towers in my 79 bronco, But they bolted in ok. If I remember, they didn't line up with the v8 bolt holes, but it's been so long, I can't remember for sure.
Last edited by havi; Oct 21, 2006 at 10:57 PM.
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From: In the Middle
Yes, using the front mount holes as a point of refernce did position the engine correctly. This was important to me because I'm using a C6 transmission and part of the shift linkage bolts to the transmision. If my engine were too far forward or rearward, the linkage would not bolt to the transmission.