12 Bolt 3.73 Posi Bundle... Worth a fart?

[veinbar]

Having my 12 bolt rear rebuilt and I'm trying to keep costs down while maintaining a respectable level of strength/dependability. I found this on Ebay and I don't know if it's worth purchasing. I've email the seller with questions, but reviews on the products are all positive. Any feedback?

http://cgi.ebay.com/ebaymotors/GM-12...ht_2279wt_1165

[Clyde65]

I would say see if it's for 3 or 4 series 12bolts,

Looking on another site ( randy's ring and pinion ringpinion.com ), the exact parts would be approx $875.00 plus shipping.

[camshaftgsxr]

id give it two farts, its an eaton posi, i would find out who makes the ring and pinion before buying though

[veinbar]

Am I wrong for thinking that $650 for all of this is a good price?

[camshaftgsxr]

thats not bad at all from what ive seen while shopping for 12 bolt parts

[veinbar]

I'm getting a little confused while shopping for these GM 12 8.875" components. I need your help...

I currently have a 3.08 ratio which means I have a 3 series carrier... Is this correct?

When shopping for rear components, I keep finding posi units for 3.73 and up carriers. Does that mean I will have to purchase a new carrier for my rear to make this work? Forgive me if this is a stupid question.

[Clyde65]

Yes, you have a 3 series, you can put up to 3.73's in a 3 series but it has to be specifically for the 3 series, the posi will go in either 3 or 4 series 12bolt.

I agree with find out brand of gear set.

[Hoods69BadBowTie]

Yep I would figure out what kinda ring and pinion first defiantly before you buy it if you do. That doesn't seem like to bad a setup or price personally.

[veinbar]

Just got off the phone with the company that sells this bundle. Here is what you get...

• The Posi Unit is Eaton, of course. http://www.summitracing.com/parts/ETN-19556-010/
• The Ring and Pinion are Richmond EXCEL. http://www.summitracing.com/parts/RMG-12BT373/
• The Installation Kit has NCB Bearings and Races.

So... Summit Pricing...
$469.95 - Eaton 12 bolt Truck Posi Unit
$165.95 - Richmond EXCEL Ring and Pinion 3.73
+ $75.00 - Bearing Kit
= $710.64 not including s/h...

Or... $650 on ebay w/ no s/h charge. I'm pulling the trigger tonight unless you guys have some compelling feedback about any of these items. If any of these items are cheap, weak, or inherently bad PLEASE LET ME KNOW.

Time is of the essence due to my truck sitting at the shop until I supply parts.

[67_SS396]

That's not a bad price. I would do it.
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[BruthaMan]

This is pretty much what I have in my 78. Can't say if it's the same vendor, ordered over two years ago, but I swapped in the same 3.73 unit. So far it's handled a considerable amount of HP/TQ that my 383 stroker has given it.

[bluex]

Originally Posted by veinbar

I'm getting a little confused while shopping for these GM 12 8.875" components. I need your help...

I currently have a 3.08 ratio which means I have a 3 series carrier... Is this correct?

When shopping for rear components, I keep finding posi units for 3.73 and up carriers. Does that mean I will have to purchase a new carrier for my rear to make this work? Forgive me if this is a stupid question.

Series shouldnt matter, that ring gear is the right size for the posi unit in the package. The only way you would need to ensure you got the right series is if you were going to reuse your existing open carrier with the new gears. Since you will be replacing it (the open carrier), the package is fine and a good price at that.

Richmond gears are good and made right down the street from me....

[veinbar]

Bought it... I'll post plenty of pics when it arrives. I can't wait to have a 700r4 to 3.73 Posi Combo. It's going to awesome!!!

[spudz]

Originally Posted by bluex

Series shouldnt matter, that ring gear is the right size for the posi unit in the package. The only way you would need to ensure you got the right series is if you were going to reuse your existing open carrier with the new gears. Since you will be replacing it (the open carrier), the package is fine and a good price at that.

Richmond gears are good and made right down the street from me....

what he said...

[camshaftgsxr]

Originally Posted by veinbar

Bought it... I'll post plenty of pics when it arrives. I can't wait to have a 700r4 to 3.73 Posi Combo. It's going to awesome!!!

its gonna be fun

[bluex]

Originally Posted by veinbar

Bought it... I'll post plenty of pics when it arrives. I can't wait to have a 700r4 to 3.73 Posi Combo. It's going to awesome!!!

It is! If your putting a shift kit and vette servo in make sure you keep your head away from the back window. Idk how many times I've told people when they ride with me and at least once on the 1-2 shift I will hear the "klonk" of heads hitting the window during the ride.
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[piecesparts]

I have been running a 12 bolt posi for years. Changed it to a 3.73 gear ratio about 7 years ago and it was worth the effort.

[veinbar]

The bundle is shipping via UPS, and it's ETA is tomorrow afternoon. I'll take plenty of pics and post them here. I'll try to get some pics of the rebuild process as well and share them. Once this is completed, My 700r4 is going in...

[veinbar]

The "Posi Bundle" arrived today!!! Here we go...

Eaton Posi Unit...



Richmond 3.73 Ring and Pinion...


Master Rebuild Kit...



Now I just have to wait for it to be installed. I can't wait to try out the taller gears.

[54Caddy]

keep us posted on how well it does have a 700r4 in my truck with a mild 350.. rear end is next project

[veinbar]

Originally Posted by 54Caddy

keep us posted on how well it does have a 700r4 in my truck with a mild 350.. rear end is next project

Will do... All things considered, I'm not sure if there's anything else I can do to make my truck more fuel efficient. After this is complete I mean... Save for getting a LS motor, which is not in my budget, and probably won't be for some time...

[bluex]

Dont expect alot, my truck only gets about 13.5 mpg.....

I might need to do this as well. Mine is just a peg leg and the guy who set up the gears apparently didnt know what he was doing, even though he came highly recommended. It howls like crazy when you let off the gas, I did use a set of used gears, but took him a new complete master overhaul kit so all the bearings should be new? I took it back twice but he said it was fine....

[piecesparts]

I get 14.5 to 15 MPG with my 3.73 12 bolt posi setup. I am runnning a 385 stroker engine, with a 700 R4 tranny (Without the lockup converter). I am running a 2400 stall converter with a set of 28.5" tall tires in the rear of the truck. The trick with the setup is to find the gear ratio and tire size that gives you the best RPMs for your highway driving. With my lopey cam and the stall converter, I set mine up to run at 2500 RPMs at 75 MPH. If you have a lockup converter and not running against a stall, then you could shoot for 2000 to 2200 at 70 to 75 MPH. You can do this by changing tire sizes, easily. Just remember the taller the tire, the harder it is to accelerate from a stop. That will eat up the fuel and make you loose mileage.

You can get into a fuel injected LS motor for about $700 dollars, motor and tranny with computer and harness. The expensive comes when you try to do the harness.

[veinbar]

Originally Posted by bluex

Dont expect alot, my truck only gets about 13.5 mpg.....

I'm hoping for better than 13.5mpg, because I've been getting better than that with a TH400 to 3.08 Open Rear combo... I know it won't improve too much, but highway driving, and in-town mpg should improve... I will document the changes, of course, and record them here.

[veinbar]

Originally Posted by piecesparts

I get 14.5 to 15 MPG with my 3.73 12 bolt posi setup. I am runnning a 385 stroker engine, with a 700 R4 tranny (Without the lockup converter). I am running a 2400 stall converter with a set of 28.5" tall tires in the rear of the truck.

This is more like it. I'm running a very mild 357ci w/ dual 2.25" longtube header exhaust, performer intake, Sean Murphy Q-Jet, Open Air Filter, 275/60/15 tires... and with the addition of the 3.73 Posi and 700r4, I expect to do 15mpg or better... High hopes, I know, but I was doing that with my old tranny and rear.