>Hi Vince,
>
>
>>You mention using the IFS out of a 77 GMC 1/2 ton. I have a 74 Chevy 1/2 ton
>>I have been trying to figure out how to use. The 2 trucks are setting
>>side-by-side in my driveway and it seems to me that the frame height
differences would cause
>>the front end of the (50 chevy in my case) to set about 6" higher than
the stock
>>straight axil. I was kind'a looking to go the other way and lower it a
bit. Any
>>hints on how you made it fit?
>
>You are correct, it will be higher than original. I didn't have the two
trucks side by side prior to starting this replacement. I went by the tips
one of the list members have posted on their site, and it is info he
received form someone else, and he noted not personally verified. The tip
indicates any 2wd, 1/2 ton Chevy /GMC, of 73 - 87 vintage(& some sub's)
will work, and lower the truck 4" in the process. It's noted the AD frame
is 28.5" wide and the 73-87 is 29.5" requiring a 1/2" spacer to fill the
gap. This is true, I used 1/2" thick aluminum on each side as the spacer.
The original straight axle centerline was 21" from the front frame horn
edge, but to get the slack from between the new saddle(77) sides I moved it
3/4" further back toward the cab (21 3/4") which shouldn't be too
noticeable. You need to drill three 1/2" holes in the bottom of each side
of the frame rail, and four holes in each side rail and shim. The late
model frames have a hump where the saddle sits, which is not in the AD
frame, thus it will set higher off the ground, in my case 4" higher than
with the straight axle. I cut 1 1/2 coils from the springs, and now the
A-arms are parallel with the ground and the tires are also 90 degrees with
the road. It now sits 2" higher than when I started, however I took the
original measurements with a 283/orig 4-speed combo in the truck. I have a
dummy (no innards) sb/350 setting there now so it's lighter than with a wet
complete motor/tranny. Note you can get dropped spindles to get the front
still closer to the ground, but of course they would be added cost to what
is a low buck swap.
> >
>I might note also the original truck(77) mounts will work as is. BUT, you
may have to notch the front cross member for pulley clearance. I'm using
the power steering box from the 77, thus I need a 3 groove bottom pulley to
drive the pwr steering pump, unless you want to fabricate one off mounting
brackets etc.
>I set the radiator in the original position and determined the fan will be
drawing air from the lower few inches of radiator and mounting bracket. My
experience with streetrods and a V8 Vega indicates you need the fan as
high as possible to get the most cooling out of the radiator. True, you can
add one or more electric fans after the fact, but why not raise the motor
now, and side step the problem. I used some 2X4X.120 rectangular tubing as
blocks on the original lower truck mounts, then mounted the rubber mounts
to these. The net effect is raising the motor approx 3"-4". No more cross
member interference and the fan is back where it was with the 283 I had in
there for 9 years, with never a cooling problem.
>The rear crossmember works as is. I made a 1/4" thick 8 1/2 inch long
plate with two tranny mount slots bolted to the four existing holes in the
center of the crossmember. When I remove it prior to final assy/paint I'll
weld a couple 1/4X1" strips along each side for strength. I had to trim
about 3/4" from the front original opening in the floor for clearance for
the TH350. This could be avoided by mounting the rear of the tranny lower,
but the mount on the crossmember would require slightly more fabrication.
This setup left me with a 2 degree downward slope at the tailshaft. I set
the pinion angle on the new pads on the 77 rear at 2 degrees also, prior to
tacking them to the housing (wish I had a hoist or pit) The two centerlines
are now parallel but about 4" - 5" apart vertically. Given the final drive
shaft length will be about 56" it's well within the u-joint drive angle
formula. I won't have the shaft cut until I have the final motor/tranny
combo in and the final welding complete on the rear axle.
>
>Sorry to drone on so long, but if anyone else is contemplating this it may
fore warn them to some of the problems and possible solutions. Keep in mind
there are probably as many ways to do this as people doing it, and everyone
has their own preference.
>
>
"Nothin lasts forever except old Fords and a natural stone" - Willie Nelson
http://home.utm.net/bfischer e-mail - bfischer@utm.net or
robert.f.fischer.jr@syntegra.com
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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