that whole pinion angle thing Zig, for your straight swap, with the same driveshaft etc, I would simply: 1a. set the OLD rear end up on blocks/jackstands so the spring perches are LEVEL. 1b. measure the distance between the perches, write that number down here ________. 1c. measure the pinion angle. write that number down here _______. 2a. obtain suitable replacement perches. 2b. cut off all perches and brackets off the NEW rear end. 2c. set the NEW rear end up on blocks so the pinion angle is the SAME as the angle you wrote down in step 1c. 2d. locate the new perches so they are centered on rear end at the dimension from step 1b. set them SQUARE and LEVEL. tack-weld them. 3a. fit-check in the truck to verify your work. 3b. weld them to the rear end permanently. Measure twice, cut once. Mike
Not sure on the GMC, but the Chevy rear end on the 3/4 ton was 4.57 regular or 5.14 RPO. With the right tires, you could climb the side of a building in granny gear and not not strain the engine!
I have a great wife! She went to Joplin yesterday when I was at school and scored me the Colorado rear end! Total cost, $315.00. It's the GT4, 373 variety. 2" narrower on mounting face to mounting face, and the pinion is 1 1/2" pushed to the passenger side instead of dead center like the original. Just like Mike (52wasp) said, the hub is bigger than the hub hole on the stock wheels. So I'm thinking about steel wheels now that aren't original, but who the heck cares, right? I do have a butt load of cutting to do. If the springs went over the top of the Colorado instead of under, I wouldn't have to change the location! Of course, the pinion angle probably would be correct, so I'd have to cut them off anyway. Again, I can't thank Mike enough for his guidance on this! I've said it before and I'll say it again I love this site!
What do Ya' mean ' I love this site'? I love your wife... no offense. She sounds like a Special Lady. You might wanna' keep her
Bill, she's got to be a special lady to put up with little bro's crap!. Send her down here if she gets tired of your crap Zig!
Okay~ Not much accomplished, but WTH do you expect from me? There was a bit of a learning curve to removing all the mounts on the new rear end. I didn't realize I was gouging the axle tube like I did on the first attempt. (First picture) I guess my welder (whoever that will be) will need to run a bead in that so I can smooth it down. Anyway, it's good to be back at it. Only one more mount to go~
better SLOW than NO (progress) Zig, it must be national wrench-on-your-Colorado-rear day! Just got longer wheel studs to mock up spacer requirements (Jegs). Popped axles out yesterday, on my way to press old studs out and new ones in this morning. For me, stuffing the 245's in the fenders means I have to get the spacer thickness just right. Good luck!
Thanks, Mike! I decided to go with Chrome Reverse wheels, (I believe) so I can skip worrying about spacers and such. Plus, with chrome rings and chrome caps, the only difference would be the roughly 2" ring of color that the original steel wheels would have...
chrome reverse wheels Zig, you might already know this, but, Wheel Vintiques, offers wheels in chrome reverse or painted with orig. looking hub caps. I'm not sure about GMC hub caps, the wheels they sell don't take orig style caps. They look orig., but are a little different in the mounting.
Zig, You may also want to consider going to your local purveyor of wheels and tires- they are more likely to assist you with tire sizes/aspect ratios, wheel widths and offsets vs buying online. May be worth paying slightly more to get rolling stock that fits perfectly the first time. Last time I was in the tire shop getting new tires for my DD pickup, I gave the help some BBQ tips while I waited. They can't WAIT to see me again!
Zig, It sounds as though the guys have you aimed in the right direction for mounting a rear end in correctly. Here's how we do it along with a bit of explanation. Roll rear end under truck and have wheel/tire combo on it that will be used. If using stock AD springs drill hole in saddle for spring center bolt 1 1/2" FORWARD of stock location. this will move the axle back and center the wheel in the fender opening much better. Measure the gap between outside of frame rail and tire on both sides and make the same. From a known point on both sides measure to the center of the axle tube and square up as necessary so the rear doesn't "dog walk". Place mounting saddles, we get them from a place that builds trailers, and install and just snug tighten the U-bolts with the pinion aimed too far DOWN. Lower truck and have it's FINAL weight on the rear end before adjusting pinion angle. Now use an angle finder (very cheap) on any surface that is perpindicuar to the crankshaft and measure that angle---usually 91-94 degrees but can vary in custom engine mounting. Two easy surfaces to get to are the front of the harmonic balancer (make sure rubber isn't squished out) and the starter mount face of the bellhousing. DO NOT use the end of the transmission out put shaft as this sags when the driveshaft yoke is removed. Finally put a slow moving jack under the front of the pinion housing and slowly jack it up till the angle meter now placed across the ears of the pinion yoke show it to be 1 to 2 degrees DOWN from the crankshaft angle. It should move even with the U-bolts snugged up. This is enough for non racing use. Tack weld the saddles to the housing, remove, and weld. The theory behind a slight downward angle is to prevent U-joint bearing flat spots by rotating the needle bearings in the U-joints and also the driveshaft yoke will be pushed further onto the transmission shaft when accelerating or pulling a heavy load from a stand still. A shaft set at zero or above zero will in the first instance not rotate the needle bearings and secondly the yoke will be pulled out of the splines on the trans shaft rather that pushed deeper. I just did this job this morning on a 52 short bed. Took 2.5 hrs. start to finish including making the saddles.
Priceless information here, very easy to understand!! Even a newbie on this job, should be able to accomblish this task. Thank you very much Evan, once again for sharing your great knowledge!!
Thanks, Evan But here's the deal~ I (first) have a split shaft. Next, I don't want to wait to have it all back together before I make the final adjustment because (first) I want to give my mom a ride in this thing before either one of us pass on, and next, as soon as I can get it out of my garage, I can pour a concrete floor in this thing which will allow me to run electrical straight to my garage instead of through an extension cord. (not good for <any> power tool/compressor.) It's a code issue here that you can only run power to a garage that has a concrete floor... SO~ What I am planning on doing is to level the old axle side-to-side in a cradle, then put a level on top of the old perch that is still attached (I haven't stripped anything from that one yet...) and get it where the bubble is dead on by raising the pinion via a slow jack. Once that is dead on, measure the angle that the pinion is setting at. Do the same with new axle. Put it in a cradle, level it side-to-side, raise the pinion to the same degree the old one was, place perches on top of axle and adjust until I find the perfect spot for level, making sure that they are also exactly the right distance from center, and weld in place. Well, not ME weld them in place, but someone who knows what they are doing, obviously. Two questions: Am I nuts for thinking this will work? Can you use a gas welder to accomplish this feat or must it be a stick weld deal? This will determine if it can be welded in my garage (gas) or if I will need to take it somewhere to be stick welded.
Who, of us which lives close to Paul and has a portable gas engine welder that can loan it to finish the welding?
Update~ I was able to remove the spring perches, shock mounts, and brake line connection bracket from my old axle and every last piece is reusable! Plus, my welder/artist buddy in Joplin (Jorge Leyva) said he'd be happy to weld the stuff on if I could have it there next week. Oh HELL yes!!!! I'll spend today and what I can this weekend getting the other fender stripped down and then start in on the hood. I'm starting to think I might have this thing where I can give my mom a ride around in it and get it out of the "garage" so I can get a floor and driveway poured. Dare to dream!!!!
nothing like a little progress to make your day! Zig, I feel your progress! Awesome! Rather than look at it as a skyscraper, look at it as ONLY 15 flights of stairs you have to climb. And a mere 14 steps to each flight! So when you get some steps completed, you have a success to look back upon (and BUILD upon). Got some stuff done this morning myself... pictures soon!
