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Cavebull.. I've re-read this thread and after crunching the numbers I'm looking at trying a 3.55 R&P, a 5 speed transmission and a 30 or 31 inch tire..
Thanks for being patient with me.. This really is a lot to think about..
Now I have to figure out where I'm gonna get all the doe to pay for this stuff..
I think I have almost solved the availability on mod questions on the rear end.. Next I need to figure out where to look for a transmission to purchase.. Any tips??
What can i roughly expect to pay for a 5 speed that will fit into my shoe box? The shifter is on the floor by the way..
Also, if I am going to do this process one step at a time and as money permits, should I start first with the tranny or should I do the rear end first? Ideally i would like to do them both at the same time.. But that may not happen..

By the way, the links you provided are kick [censored].. I crunched the numbers and your right on..

Just a couple things to kick around before you go jumping into the flames. Adding a T5 and sticking in the correct differential is not something to be tackled without some very specific skills, equipment, time and a small bucket of money.Lacking in any one of these items is going to cause you untold grief!

Having walked down this road a number of times in the past didn't make it all that easy of a transition. Granted, there are folks here who would be willing to offer some suggestions, but when you get right down to the nuts and bolts....the ball will fall into your court. You'll also have to weigh the cost of the components against what you'll be saving in fuel economy. I've documented the conversion process in my Webshots....and suggest you check out the conversion process before you make any committments. You might be wiser to focus you efforts on getting your current setup upgraded....a new R&P or even a swap to a 3.08 with your current 1:1 top gear might be the most logical choice. Of course, it's your call......we'd just hate to see you get in over your head and wind up with a truck that wasn't on the road.

Fla54Chevy3100,
This site has been most helpful in many ways.. My first inclination is to go with the 3.08, a little bigger tire and call it quits.. My only fear with that is I worry about the truck bogging down with that high of a R&P set up.. Of course I'm not towing anything and I do have that first gear if needed to get off the line.. But without driving it with the that particular R&P installed I wouldn't know..
What do you think?

Your concerns about getting too tall a R&P setup are not unfounded. Going too tall will cause you as many problems, if not more than going too short. It's the happy medium you're looking for, and unless you've got a dyno, or someone who is running the same setup, getting it right is basically a crap-shoot. That's why we all, at one time or another, do a little trial and error on our own, after we've crunched the numbers and limited the range of options. "Experience is the best teacher, but it gives the test first and the lesson after."

If your truck was running basically the same configuration of engine, gearing and tire size you could get the same final results as mine. I've discovered with the 235, that unless you go with a fairly radical cam (which I haven't) that the torque band is strongest between about 1900 and 2400 rpms give or take a 100 rpms. If you wanted to match your gearing to get the highest vacuum reading at a specific cruise speed, you would want your engine to be turning in the 2100-2200 rpm range. On my setup, I'm just a hundred or so rpms below that mark at 70 mph. But as luck (?) would have it....I've found that I'd rather cruise at a lower speed, so I'm going to go with a shorter gear. This would let me max my vacuum at a lower ground speed.

So did I calculate this R&P change? Nope, I just increased my ground speed, watched my vacuum come up higher at 75-80 mph, and recognized that a shorter gear, which in my case would be a 3.55 or 3.73, would get me into the "sweet spot" of my engine at the mph I most wanted for cruising. The Camaro diff, which I've found is plentiful, reasonably priced and adaptable (62" wide) in a 5 lug pattern, matches my current rim bolt patterns and will give me the gearing I need. The S10 Blazer 4wd diff is said to be the correct width and it may be available in the ratios you need. Granted, there are some mods that have to be made but I know some of the guys are running them. Hopefully, someone will pipe in and confirm that a 3.08 will put you at 2100-2200 at your chosen favorite cruise speed.

You mentioned earlier that you were running a 15" rim with a 24-25" tall tire in a 75 series....you need to check that, as that would have you running a very skinny tire. I've found that the 235/75/15 at 28+" tall, fills the wheel well nicely on a 7" rim.

As I mentioned before, you've just got to carefully gather your information, sort out which will work for you, access your skills for doing the work yourself.....and most importantly, check that bucket to make sure you've got the backup money to get the job done correctly. I hope this helps.

Dave

Hi all.. Still fighting the good fight..
Found the factory optional high speed ring and pinion kits.. It's a 3.38.1 ratio and an outfit called Patrick's in Arizona sells them.. They apparently are made for the 1955's-1962's 1/2 ton rears..
I'm not so sure that is the avenue I should take.. The rear i have is a solid housing (no seperate 3rd member etc..)
I've been getting quotes from a couple different rear end specialists and they are all suggesting I try for a later model rear.. Simply because the parts are more available and also the later model rear ends come in sections so you can work and maintain without having to deal with the entire axle and such..
Does anyone know when Chevy changed from the HO 52 rears to the 12 bolts on these half tons?
I have been scowering the junk yards and have found a 12 bolt from a 67.. It is a 5 lug, so I don't know if that matters?
Any input would be appreciated..

I don't want to be a Johnny Come Lately - I told you so guy but the reason the 3:55 for AD's work and the 3:38 for TF's work is because a thousand guys have been down this road before and Patrick was one of it's pioneers. They discovered the answers so don't be afraid to learn from the best. If there were better solutions Patrick would have those gears made up.

I know, I know, every generation has to learn everything on their own but this ground has been plowed so many times. Just pick up the phone and call Patrick. Talk to him, he's a great guy and an Inliners Hall of Fame member. So is Tom Langdon. Call him too. These guys have real knowledge.

Yes I am an Inliner's member, fan and booster and I urge all of you to locate your local or nearest Chapter and join too. Need help on who and where?...just give me a shout. This site is a wonderful resource and I am priviledged to help out with it but nothing beats the face to face interaction of a real conversation with a real person. (not to mention seeing their truck or car)

Hey fellers..! Just wanted to update you guys and let you know what I ended up doing..
Ran into an old friend I hadn't seen in years.. I remember he was an old Chevy truck guy from back when.. So we started talking shop about trucks of course..
Anyway, turns out he had a 12 bolt rear end from a 1969 C-10 long bed.. It had a 3.07 ring and pinion already in it..
So we swapped out the whole rear.. It was in great shape.. We replaced the wheel bearings and seals, pinion seal, "C" clips, cover gasket and some other minor things..
The only thing that was a pain in the butt was we had to break the welds on the "U" joint brackets and move them a couple inches and shorten the stabilizer bar.. Then of course got the plum tools out to make sure it was sitting at exactly the right spot.. Other than that it bolted right up like it was made for it..
It rides like it's on butter now.. Smooth and much lower rpm's.. My tack reads about 2400 rpm's at 57 mph.. Which I know isn't right because i'm passing cars in the third lane on a 5 lane freeway..
Today i had a cop hit me with his radar while I was driving.. My speedometer said I was going 20 mph and he said i was doing 26..
So obviously I have to get my speedometer and odometer re-calibrated..
Also, I'm still running my 25" tires.. They are pretty new so I wanted to get some more use from them before I size up the tires.. Probably I will end up putting a 26" or 27" tire on there and calling it quits..
At this point it is hard to say how this has effected my fuel economy.. Once I re-calibrate the speedometer and the odometer I'll have an exact number on mileage.. But one thing is for sure, my truck is loving the new rear end.. It is definitely giving my motor a break..
One last thing.. I plan on taking it into a regular rear end place and paying them to do a diagnosis on it.. Even though it appears to be operating well, it is a used rear end and it is old.. So maybe might need some shims replaced or some gears..
I'll sleep better once I have them go through it..
For now I'm stoked on what I did.. This was also a good move because the parts for these 69 rear ends are more available and the maintenance on them are much easier..
Thanks to all that helped me on this thread..