Making a 3/4 ton into a 1/2 ton...what I did!

[westofb]

Okay, just thought I would provide info for anyone considering this conversion, and I did not take time to take pics....SORRY!

My starting point was a rust free CA 75 3/4 ton Silverado 454/400 with 63k. I am going to static drop the truck with spindles/ cut coils and a rear flip. I started on the front suspension today. I got it all put together and the following is a list of the parts I used to make it happen:
1) 1/2 ton lower control arms, 3/4 tons have larger ball joints.
2) 1/2 ton upper ball joints, they fit the 3/4 ton uppers just fine, was going to use 1/2 ton uppers, but the studs in the frame/ front cross member where they attach are larger than the 1/2 ton and they will not fit.
3) I used 1/2 ton lowering spindles 2.5" drop with 1.25" thick rotors, I had the complete 1/2 ton setup for these spindles including rotors backing plates and calipers. Oddly enough, when installing these I notice the 3/4 ton calipers looked the same, and sure enought they bolted right onto the 1/2 ton spindles, so it saved me the effort of having to bleed the front brakes.
4) The 3/4 ton tie rod ends bolted on to the spindles without modification.
5) I used 1/2 ton coils and cut one coil off the bottom of the spring.

So there you have it, just a few actual parts are needed to complete the swap from 3/4 to 1/2 ton. measuring from the fender lip to the ground the front end of the truck now sets about 8" lower than it did as a 3/4 ton. I am using 20" Boss wheels with 275/40 R20 tires.

I will post updates to this thread on what it took to change the rear suspension to 1/2 ton, and will try to take some pics and post them also!

[skhurst18]

How's it going? I read your thread. Not quite familiar with some of the terminology. I am interested in converting my 1/2 ton 87 LWB to a 3/4 ton. Any suggestions?

[N2TRUX]

Reverse his procedure.. What terms are you confused on?

[skhurst18]

Not too familiar with the parts of the suspension. I compared measurements from a 1 ton to my 1/2 ton and noticed the holes for either the 3/4 ton or 1 ton are already there. I measured from the front leaf spring hangers to the rear and measured the distance between the bolts on the upper A-arm assembly into the frame. Maybe you can share some of your wisdom.

[westofb]

Okay, the last couple days I have worked on and finished the rear suspension. I am pretty sick of drilling holes (24) and removing rivets (16), am just glad I got it all done. I had to first remove the 3/4 ton parts including the rear axle, the leaf springs, and the rear spring hangers. I had to move the rear spring hanger forward since the 1/2 rear springs are about 4 inches shorter eye to eye as compared to the 3/4 ton ones. After getting the everything off that I could not use, I began installing the 1/2 ton components which included the rear axle (open diff with 2.56 gears, building it to cruise not race), rear springs, the rear spring hangers (3/4 ton rear hangers are identical except they have a longer blot through the hanger that attaches to a brace that is riveted to the bottom of the frame), a set of c notches from Mcgaughneys (not sure on the spelling), and I used a set of Mopar axle perches to make my own flip kit.
The rear spring install was pretty straight forward, the front fit in the 3/4 ton hanger, then I had to measure the donor truck to locate the rear hanger, then simply drilled some holes through the frame (I had extra bolt with the c notch kit so I used them, 1/2 inch grade 8 with locking nuts, a little over kill, but saved a trip to the hardware store, I think 3/8 inch bolts would have worked just as well). I then installed the c notches, actually I could have got by without them, there is plenty of clearance, but at the time I ordered them, was intending to use the 3/4 ton springs and they set closer to the frame than 1/2 ton springs do. I them installed set the axle on top of the springs and mocked up my home made (store bought parts) flip kit. After researching flip kits, I decided to locate my axle back one inch, so had to drill the mopar perches 1 inch off center with a 11/16 inch bit to allow them to sit down on my spring packs locator pin. I then mounted the u bolts in place and discovered that I had to also drill the u bolt plate 1 inch off center to allow the nuts on the bottom of the locator pin to protude through them. I them just snugged everything down, set it back on its wheels to get it at ride height so I could adjust the rear end to get my pinion angle set. Once I was happy with the pinion angle, I tack welded the mopar perches to the axle tube. I them jacked it up, removed the u blots, turned the axle upside down and welded in the perches. I then simply bolted everthing back in place. I did not use shock extenders (actually forgot to order them) and bolted on a set of monroe gas shocks. Without the shock extenders, the shock bolt was dead center of the u bolt retaining plate, so I had to install the shocks prior to re-installing the u bolts and the retaining plate, installed the shocks with the nuts toward the rear pumpkin. I did have to have the drive shaft shortened 1 1/2 inches, I kept the stock 3/4 ton 2 piece drive shaft and used a u joint with 2 different cap sizes (one to fit the 3/4 ton drive shaft and one to fit the 1/2 ton rear end), I believe the part number was 348 at O' Reilly's.

All in all, it wasn't too hard to complete the conversion. The hardest part was having to figure out what parts I had to have to make it work. I was glad I had a complete 1/2 ton truck around for parts and to get measurements from.

[westofb]

Here are a few quick pics of the now 1/2 ton truck! Sorry about the poor quality, taken with cell between thunderstorms today.

[westofb]

Originally Posted by skhurst18

How's it going? I read your thread. Not quite familiar with some of the terminology. I am interested in converting my 1/2 ton 87 LWB to a 3/4 ton. Any suggestions?

I would agree with N2TRUX, it would be just the reverse of what I did. You will need the following parts to get it done:
1. 3/4 ton lower control arms with ball joints.
2. 3/4 ton spindle rotors backing plates, if your truck has 1.25" thick rotors they should bolt onto the 3/4 spindles (my 3/4 ton fit the 1/2 ton)
3. 3/4 ton upper ball joints, will fit your 1/2 ton upper control arms

that should get your front done, for the rear you will need these parts:
1. 3/4 ton rear end complete
2. 3/4 ton rear springs

your rear spring hanger is the same as a 3/4 ton, just lacks the extra brace that attaches to the bottom of the frame, as far as that goes, the front spring hanger has an extra brace that attaches to the bottom of the frame as well. Of course you will have to relocate your rear hanger towards the rear to accomodate the longer 3/4 ton springs. Should be a pretty simple conversion. I did mine by myself, took me about 3 and a half full days to get it done.

Too bad you weren't a little closer, I have the parts you need to make yours a 3/4 ton...LOL!

[bluex]

What color blue is that, I like it!

[westofb]

Originally Posted by bluex

What color blue is that, I like it!

I don't remember off top of my head, it is a nasson base clear, picked it out of the spectra master book, will try to remember to get the paint code off the can for you. Oh, yeah, thanks, I like it too!

[KQQL IT]

Could'nt you reem a 1/2 ton spindle to accept 3/4 ton ball joints?

[westofb]

Originally Posted by KQQL IT

Could'nt you reem a 1/2 ton spindle to accept 3/4 ton ball joints?

I suppose you could, if you had the right tools, I would think you have to be very careful not to over reem the hole. I have heard they make drop spindles to fit the 3/4 ton ball joints and convert the front to 1/2 componets. I already had the 1/2 ton drop spindles, and had access to the donor truck so I went that way.

[westofb]

Just an update to my process, I am having trouble getting the right gears to correct my speedo. I went to TCI's website, great info there and they have a place there where you plug in your tire diameter (have a way to figure that for you too as long as you the the nomeclature of the tire), and rear axle ratio to figure what gears you need to correct you speedo. Well to make a long story short, the gears I need for my TH400 do not exist...I guess GM never intended to put a 400 ahead of a 2.56 rear gear. I will have to check with a couple of places I found online to get a ratio adapter to correct the speedo. Any suggestions would be appreciated, the ratio adapter looks to be my only option, well I am going to give the local Chevy dealer a call first of the week to see if they can come up with the gears I need, from the TCI website, I was able to come up with several combos of gears that will correct the speedo, they just don't have the ones I need.

[KQQL IT]

Originally Posted by westofb

I suppose you could, if you had the right tools, I would think you have to be very careful not to over reem the hole. I have heard they make drop spindles to fit the 3/4 ton ball joints and convert the front to 1/2 componets. I already had the 1/2 ton drop spindles, and had access to the donor truck so I went that way.

It used to be a popular pre runner thing. Putting 3/4 joints and arms, because thicker a/Arm and beefier ball joints. I do like the blue tho

[westofb]

Forgot to mention, got the hood on today. Had to reloosen most of the bolts on the front clip and slide everthing towards the passenger side to get it squared up to the hood, sorry no pics was a nasty rainy day! On a side note, the bumper fits the front end better now too. It is slightly bent on the drivers side corner and figured that was the reason it sat closer to the fender than the passenger side did, but everything was just racked a bit out of square.

[westofb]

No progress today, has been raining and had to go to work!

[Colesnsty68]

Just a quick question im sure you said why but im kinda in a hurry, how come you moved the rear leaf spring mounts forward?

[3r!c84]

damn that exhaust looks good!!! and all the other work lol

[skhurst18]

Originally Posted by westofb

I would agree with N2TRUX, it would be just the reverse of what I did. You will need the following parts to get it done:
1. 3/4 ton lower control arms with ball joints.
2. 3/4 ton spindle rotors backing plates, if your truck has 1.25" thick rotors they should bolt onto the 3/4 spindles (my 3/4 ton fit the 1/2 ton)
3. 3/4 ton upper ball joints, will fit your 1/2 ton upper control arms

that should get your front done, for the rear you will need these parts:
1. 3/4 ton rear end complete
2. 3/4 ton rear springs

your rear spring hanger is the same as a 3/4 ton, just lacks the extra brace that attaches to the bottom of the frame, as far as that goes, the front spring hanger has an extra brace that attaches to the bottom of the frame as well. Of course you will have to relocate your rear hanger towards the rear to accomodate the longer 3/4 ton springs. Should be a pretty simple conversion. I did mine by myself, took me about 3 and a half full days to get it done.

Too bad you weren't a little closer, I have the parts you need to make yours a 3/4 ton...LOL!

Thanks for the info. I went to a local pullapart and took some measurements on a 3/4 ton. Everything that you described made perfect sense. I took a look at my frame and the holes for the transition are already there. Good luck with the rest of your project.

[cableguy0]

Before you beat your brain too bad trying to find speedo gears. I would wait and drive the truck first. That ratio isnt going to be that great just cruising around. The truck will do about 100mph under 3000rpm. You will want at least a 3.07 gear if not a 3.42. The rpms are constantly going to be too low.Mileage will likely be nonexistent. With a 29 inch tire that truck isnt going to be able to get out of its own way in town. At 40mph you will only be turning 1200 rpm. Not trying to be negative just throwing it out there. I would look for another gear ratio before you get too tied up in that rear.

[CenValyCali]

Originally Posted by westofb

Here are a few quick pics of the now 1/2 ton truck! Sorry about the poor quality, taken with cell between thunderstorms today.



Attachment 576188

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Looks great! I need to add the notch to mine and then add the longer shackles.

[westofb]

Originally Posted by cableguy0

Before you beat your brain too bad trying to find speedo gears. I would wait and drive the truck first. That ratio isnt going to be that great just cruising around. The truck will do about 100mph under 3000rpm. You will want at least a 3.07 gear if not a 3.42. The rpms are constantly going to be too low.Mileage will likely be nonexistent. With a 29 inch tire that truck isnt going to be able to get out of its own way in town. At 40mph you will only be turning 1200 rpm. Not trying to be negative just throwing it out there. I would look for another gear ratio before you get too tied up in that rear.

Kind of the reason I went with the rear I did, I want to be turning around 1800 or so at 60-70 mph. It does have a big block, so ought to have plenty of torque to lug it down the highway. It will not be a daily driver so fuel mileage is not that much of a concern....besides, I did not think big block and resonable fuel mileage went hand in hand.

I did take it for a short spin today, seemed to drive okay with the rear, speedo was off terribly, I think I was cruising around 70 or so (keeping up with traffic) and speedo was reading like 30-35 mph. I don't have a tach installed so I have no idea what the engine was turning, but when I stepped down on it, it had plenty of get up and go!

Oh, and I should mention, this rear came out of the donor truck, was a plain jane 1980 stepper, only options were power steering, 305 v8, and automatic...I bet it was a real speed demon in it's day...LOL!

[westofb]

Originally Posted by bluex

What color blue is that, I like it!

Checked the paint can, like I mentioned is dupont nasson paint, spectramaster blue-effect paint code number bm126.

Originally Posted by Colesnsty68

Just a quick question im sure you said why but im kinda in a hurry, how come you moved the rear leaf spring mounts forward?

The half ton springs were about 4 inches shorter than the 3/4 ton springs I replaced, so I had to move the hanger forward.

Originally Posted by 3r!c84

damn that exhaust looks good!!! and all the other work lol

The exhaust is made of up unknown manufacture long tube headers, summit brand welded race mufflers, and 3" tubing installed by the local muffler shop. I am quite happy with it, has a very deep exhaust tone, moderately loud..very similar muffler to flowmasters (hell they may be flowmasters in a summit box!).

[westofb]

Updates on progress, yesterday got the front of the bed worked down and painted. Today I got the bed installed on the truck, welded in the steel roll pan and some of the trim holes. Hopefully tomorrow I will make some real headway on the body work on the bed. Here are some pics of the progess, I really like the stance of the truck!

[skhurst18]

What method did you use when you removed the rivots from the frame? Just curious because I have located the parts at a salvage yard and I need to try and remove them within one day.

[westofb]

Originally Posted by skhurst18

What method did you use when you removed the rivots from the frame? Just curious because I have located the parts at a salvage yard and I need to try and remove them within one day.

I used an 3" cutoff saw to cut a x in the head, then an air chisle to cut off the rest of the head, the air chisle was used to drive out rivet. If you are going to do this in a salvage yard, I would recomend a very large and sharp chisle to cut off the heads, a punch to drive them out with, and a bf hammer to strike the chisle/ punch with!

It took me a day and a half to strip the donor and about 3 days to remove and replace parts on my truck. Of course, I had no real idea at the time what I needed to do to get it done, and spent a lot of time measuring and check parts to see what combo I need to make it work. So, I guess you are one step ahead of me there!