What's the "best" way to convert to a posi rear end?

[99-LS1-SS]

I've got an open differential and I want to convert it to a positive traction rear end as well as putting a taller (more highway friendly) gear in it. What is the best way to achieve this?

Thanks.

[cdowns]

i've found about the best longterm soulition is to drop it off at a good shop and pick it up completed in a few days

[billybaloo]

That's funny stuff right there.

[prostreetC-10]

Depends on if you mean "best" as in "least expensive". BEST way is as above and just give it to a rear end shop and have them go through everything (bearings....etc.). SOMETIMES, the most economical way to achieve what you want is to find another rear end that has at least one of the two things you want. Either find one with a good posi or the right gears and add the missing component. Of course there is always the chance of the part you are buying it for might be worn out or on it's way which then leads you back to the first suggestion!

[GASoline71]

Originally Posted by billybaloo

That's funny stuff right there.

There wasn't anything funny about it. It's the truth. Unless you know how to set up a rear end with a new posi-traction carrier and new gearset... you're better off dropping it off at a shop.

Gary

[AusTx68]

A couple weeks ago my front seal went out and lost all the oil. I thoroughly toasted the gears. It was the perfect opportunity to go posi. After doing the research I realized it takes special tools and knowledge to get it right. So I picked up an Eaton posi, 4.11 gears, and install kit from Summit for $695. When the shop got it apart they found it needed axles, bearings, and pinion yoke. The price of labor, axles, pinion yoke, and axle bearings came to $805. So for $1500 I have differential with all new components.

[GASoline71]

I'm currently stockpiling parts for a rearend rebuild. Then my bro-in-law is gonna rebuild it for me. He does it at the shop he works at. But we'll do it at his garage at home, and for his labor all I have to do is buy him a fifth of JD.

Gary

[99-LS1-SS]

I'll likely go to a shop.

Are the 5 lug 12 bolts 2wd trucks 30 spline?

Are there any carrier brands that I should look at or stay away from?

I'm considering a 3.08 or 3.42 ratio. Does anyone see an issue with these ratios?

[fleetsidelarry]

I personnaly don't have a problem with my 3.07, suits my driving style just fine. depends on:

are you-
going to do any towing
going to haul any heavy loads
wanting quick acceleration, or easy cruising
do you have an OD transmission
is your engine suited to pulling the tall gear

if you have an OD, the 3.42 would probably be a good choice, although, as I said, the 3.07 (3.08) works fine for my easy driving style

[prostreetC-10]

To me, there is a big difference between a 3.08 and 3.42. I think a 3.42 is an awesome ration but I would never have a 3.08 if given the choice. Just too tall. There is a bigger "notice" between a 3.08 to 3.42 vs 3.42 to 3.73. The 3.42 keeps you from just screaming down the highway but yet gets you rolling much quicker than the 3.42.

You haven't said what gears you have now just be careful not to have a motor/stall matched for your setup and kill it with a gear change. In other words, if you have a healthy motor with a bigger cam, the gear change can kill your performance.

[99-LS1-SS]

I'm not sure what gear I have right now. I haven't checked it yet. I'll check tonight.

I don't have an engine or transmission yet.

I doubt I'll pull much with this truck. It will be a hauler only in emergencies and then it wouldn't pull anything larger than a ski boat. I like the cruising aspect more than the screaming aspect. The engine I'm considering at the moment is the TBI 502 and I am leaning towards a 4L80E transmission. I'm also going with a Yank 2600 converter. Given the fact that 4th gear is a .70 ratio would the 3.42 be a better "all around" gear? I want this truck to be easy and fun to drive. I don't want to be turning 3500 rpms on the highway if I have to travel anywhere.

[prostreetC-10]

O.D. or no O.D. should be a BIG difference in the ration you deicide to go with. I think that alone will eliminate the 3.08 choice. a 70 OD is pretty high. You really need to figure out what is in it now. A 3.73 might even be better with that trans.

[99-LS1-SS]

I agree. I really want an O.D. and a lockup converter so I think, with the help of you guys, I've made my decision on the ratio. Now I have to find a shop around here that does quality work. I've heard a lot of horror stories about rear ends not being setup right.

[prostreetC-10]

Yeah be careful.....I had a girlfriend once that had some work done on her rear end and got it all messed up! lol

[Clyde65]

I would leave the 3.73's in there, with the OD tranny and the 502, you will still be able to run highway miles without winding that BB up too much. have you ran the numbers? I mean tire size/gear ratio/trans ratios and see what RPM you will be at? might be a good idea before you start looking at more $.

[Pop's C-10]

If you happy with what ratio you find..you can get a powertrax unit & jus slip it in..not gear set up...you can do it @ home..

*waits for folks to shot that idea down*...lol

[99-LS1-SS]

Originally Posted by Clyde65

I would leave the 3.73's in there, with the OD tranny and the 502, you will still be able to run highway miles without winding that BB up too much. have you ran the numbers? I mean tire size/gear ratio/trans ratios and see what RPM you will be at? might be a good idea before you start looking at more $.

Are you confident the rear gear ratio on a 1972 2wd (with a 307) is 3.73?

[99-LS1-SS]

According to an online calculator that I ran across, I would be turning 2000 rpms at 65 mph with a 3.42 and and 2200 rpms at 65 mph with a 3.73. I like the 2000 a little better.

[prostreetC-10]

Yeah but 2,200 is nothing at 65 mph. I'd love to be able to spin that low. Really give it some thought because there is give and take here.

[usmcchevy]

Originally Posted by 99-LS1-SS

Are you confident the rear gear ratio on a 1972 2wd (with a 307) is 3.73?

Normally the 2wd V8 trucks got 3.08s. I6 trucks were 3.73.....normally

[fleetsidelarry]

prostreet and I seem to come at this from two different directions basically because of what I assume is a difference in our driving requirements. I love my 700r4/3.07 (or 3.08 whatever it is), I'm at around 1800 at 65. I've got a basically stock 350. He's got what must be a really cool 496 with ram dual 4's.

many modern light-duty 1/2 tons now-a-days are going to have an OD transmission with something like a 2.73 rear ratio.

if you indeed go with a 502, you're going to have so much torque its not going to matter, the motor will pull any gear you want to put back there. As Prostreet alluded to earlier, give some thoughts to what components you're going to use on the engine, particularly the cam and intake/carb and selecting a combo that likes the RPM you want to run at. I spend most of my time in the 1500-3000 band, particularly around 2000 and I like it (BTW , I do a lot of driving at 45-50, and just keep it in drive, not over-drive, which still gives me the RPM range I and the dual exhaust like). But different strokes for different folks. if you pick a cam and intake combo that likes 4000-5000, you should gear accordingly.

[billybaloo]

Originally Posted by GASoline71

There wasn't anything funny about it. It's the truth. Unless you know how to set up a rear end with a new posi-traction carrier and new gearset... you're better off dropping it off at a shop.

Gary

Sorry, I saw humor in the statement. It's like, there is more than one way to skin a cat. But the best way - take it to a cat skinner.

I know, whats' cat skinning have to do with rear ends?

[99-LS1-SS]

I see both points.

As far as picking the "right" parts, (at the moment) I'm going with this EFI 502 which makes peak torque at 3500 rpms. I WILL drive this truck hard sometimes but, most of the time I'll be cruising around in it. I agree that the 502 torque should be plenty and that's why I was even considering a 3.08.

My goal is to have a non-radical, wife/family friendly cruiser. I just came from a M6 G8 GXP that I put a 2300 TVS supercharger on and it was NOT wife/family friendly after I got done with it. I don't want to jump from the frying pan into the fire.

Originally Posted by fleetsidelarry

prostreet and I seem to come at this from two different directions basically because of what I assume is a difference in our driving requirements. I love my 700r4/3.07 (or 3.08 whatever it is), I'm at around 1800 at 65. I've got a basically stock 350. He's got what must be a really cool 496 with ram dual 4's.

many modern light-duty 1/2 tons now-a-days are going to have an OD transmission with something like a 2.73 rear ratio.

if you indeed go with a 502, you're going to have so much torque its not going to matter, the motor will pull any gear you want to put back there. As Prostreet alluded to earlier, give some thoughts to what components you're going to use on the engine, particularly the cam and intake/carb and selecting a combo that likes the RPM you want to run at. I spend most of my time in the 1500-3000 band, particularly around 2000 and I like it (BTW , I do a lot of driving at 45-50, and just keep it in drive, not over-drive, which still gives me the RPM range I and the dual exhaust like). But different strokes for different folks. if you pick a cam and intake combo that likes 4000-5000, you should gear accordingly.

[99-LS1-SS]

Originally Posted by billybaloo

Sorry, I saw humor in the statement. It's like, there is more than one way to skin a cat. But the best way - take it to a cat skinner.

I know, whats' cat skinning have to do with rear ends?

I'll let the "cat skinner" do his magic on this project.

[prostreetC-10]

Originally Posted by fleetsidelarry

prostreet and I seem to come at this from two different directions

And yet I completely understand your direction at the same time Larry. It truely is personal pref.

Man that's a lot of motor for a cruising family truck. I have to go check the rules book too because I think you can be cited for having a 502 and not running the crap out of it.