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#1 |
Registered User
Join Date: Feb 2011
Location: Modesto, CA
Posts: 2,188
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Rear End Posi Help!
So, i just decoded my rear axle and it's an HB which if I am correct, is a 3:07 rear end, and I cracked it open to confirm it's posi. Unfortunately, the truck has a 700r4 which is no bueno with the rear end gears for overdrive. My question is, can I swap out the rear gears without swapping the posi unit? I see 3:73 gears through companies for anywhere between 150-200 which isn't bad at all, I just don't want to have to dump another 500+ on a posi unit. Any help is greatly appreciated, thanks!
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#2 |
Registered User
![]() Join Date: Apr 2012
Location: Stillwater, Oklahoma
Posts: 874
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Re: Rear End Posi Help!
I'm not an expert at all on this, but I have been researching options for my own rear end.
I am pretty sure you can change the gears and not change the posi unit, but since you have 3.07's you have a 3 series carrier. A 3.73 requires a 4 series, but...... They make thicker aftermarket 3.73 gears that should fit in your housing. Good luck.
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1971 C/10 SWB, 15x8 Rallys, 4.5" X 7" static drop, C-notched, 350/350, 3.73 Posi. .........A 383 and Gear Vendors are on my bucket list. 1972 GMC 4X4 K1500 Survivor - Sold No matter what problems life throws at you, your time on Earth can be incredibly fulfilling and rewarding.....if you just lower your expectations. -Phil Dunphy |
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#3 |
Registered User
Join Date: Feb 2011
Location: Modesto, CA
Posts: 2,188
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Re: Rear End Posi Help!
I just started to understand the 3 and 4 series carriers and I understand that they have all the gears in 3 and 4 series (summit racing has them). Thanks for the info though!
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#4 |
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![]() Join Date: Oct 2012
Location: Newhall CA
Posts: 1,195
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Re: Rear End Posi Help!
Don't go Cheap on the gears,cheap gears are made in China. and 3.73 is a good ratio for the 700r4.
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69 SWB 780hp Hellcat powered, manual 6 speed, currie 9 |
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#5 |
Registered User
Join Date: Feb 2011
Location: Modesto, CA
Posts: 2,188
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Re: Rear End Posi Help!
Good advice, I won't be going cheap. It just seems most all brands are similar priced. I checked Richmond, and a couple others. This truck is just a cruiser so I'd be pretty hard pressed to even chirp the tires. Thanks for the replies!
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#6 |
Registered User
Join Date: Apr 2011
Location: Klein Texas
Posts: 3,852
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Re: Rear End Posi Help!
India is a major supplier of gearsets. Even name brand ones are made there.
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My Classics: '72 K20 Suburban + '65 Dodge Town Wagon '72 Corvette Roadster +'67 Corvette Roadster '73 Z-28 Camaro '63 Ford SWB Uni Pickup '50 Ford Coupe |
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#7 |
Registered User
Join Date: Mar 2010
Location: a t w a t e r cali 95301
Posts: 10,713
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Re: Rear End Posi Help!
ok heres what you can do thy make an adapter ring to gtom from 3.07 to 3.73 and keep your orignal 3 series carrier if you buy that adapter ring along with a new 3.73 ring and pinnion as well as a new crush sleeve and while your at it bearings for the carrier and pinion and new seals then you should be able to install no problemo
carrier breaks: 3 SERIES CARRIERS: 3.07, 3.42. (3.42 and lower are all 3 seies) 4 SERIES CARRIERS: 3.73, 4.11. ( above 3.42 in ex: 3.55 are all 4 series) there is no way to use a 4 series carrier with 3 series gears. it will not happen. hopefully this will be a referece for anyone in the future. |
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#8 |
Senior Member
Join Date: Jan 2003
Location: daytonabeach
Posts: 22,956
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Re: Rear End Posi Help!
brand new gears and a 40 year old posi ?? that doesnt sound like a great plan
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71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY |
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#9 |
Registered User
Join Date: Feb 2011
Location: Modesto, CA
Posts: 2,188
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Re: Rear End Posi Help!
I plan on having the posi rebuilt as well, I just didn't know if the posi is specific to the ring and pinion as in, I'd have to buy a new carrier, and new ring and pinion. Having it rebuilt saves about 300 bucks.
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#10 |
Registered User
Join Date: Aug 2010
Location: Edwards, CA
Posts: 7,503
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Re: Rear End Posi Help!
To keep thi simple.
The 12 bolt truck cases (open or posi), from the factory, were sized for 3.73 ratios and up (higher numerically) such as 4.10. Or 3.40 down numerically like a 3.08. If you have a factory 3.08 then that would be a 3 series case and to install a lower stock ratio (higher numerically) like a 3.73 or a 4.10 from another truck would require a case chage. However the aftermarket has stepped in and offers truck gear sets in 3.73, 4.10 and 4.56 that will fit the 3 series case due to dimension changes in the gear sets. A quick check of about any parts catalog (Jegs referenced) will show gears that would allow you to keep your 3 series case. Jegs has both Eaton and Jegs branded sets from 3.73 up to 4.56 on a 3 series case. Depending on wear or damage it might be cheaper to replace the case with a new unit, maybe even step up to an Auburn. If money is really tight almost any 6 cyl C10 will have 3.73 gears if swapping a rear axle out buys you time to build a dream axle up. Finally before you go ripping everything apart I would recommend doing the math for your intended tire and gear selection in OD then finding/borrowing a set of used tires sized to mimic the gear changes. This will give you a real world feel before spending a lot on hard parts then wishing you had gone a little lower or higher.
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Thanks, Tim * VIN/Model Decoders * Power Team Charts (engine/transmission/gear ratio) * Post Your Pickup SPID ** Blazer SPID ** Suburban/Panel SPID * RTFM ... Read The Factory Manuals... download 'em here Highlanders ** Do you have a 1972 Plaid Pickup? ** Plaid Blazer ** Plaid Suburban Last edited by SS Tim; 06-24-2014 at 10:00 PM. |
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#11 |
Registered User
Join Date: Mar 2014
Location: Wilmington
Posts: 27
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Re: Rear End Posi Help!
If it is just a cruiser why even worry about posi?
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#12 | |
Account Suspended
Join Date: Jan 2007
Location: Tucson
Posts: 2,183
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Re: Rear End Posi Help!
Quote:
When you go to put the new one on, preheat the wife's oven to 400 degrees and bake that thing for 20 minutes. It will expand enough to slip on but be sure you have the bolts handy. You will need to get two in finger tight before that ring gear shrinks! Then it's just a matter of pulling the pinion gear and pinion bearing and replacing the old pinion with a new one. Mark Williams has a pretty good tutorial on how to do this here: http://www.markwilliams.com/bulletproof.aspx but there are many others. If you happen to have the overhaul manual for your truck it's in there with pictures! If you don't have that book you can get one on CD Rom here: http://www.faxonautoliterature.com/1...al-P20755.aspx Gearsets, bearings, install kits and new springs and clutches for your posi can be had at reasonable price at Drive Train Specialists. DTS uses ONLY American made parts so you aren't getting Chinese crap for bearings and gears. A 3.73 R&P set will be about $190.00. http://www.drivetrainspecialists.com/ If you decide to rebuild your posi carrier, use the 600lb springs, not the 400's or 800's. Last edited by Fitz; 06-25-2014 at 01:00 PM. |
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#13 | |
Registered User
Join Date: Mar 2010
Location: a t w a t e r cali 95301
Posts: 10,713
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Re: Rear End Posi Help!
Quote:
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#14 |
Registered User
![]() Join Date: Apr 2012
Location: Stillwater, Oklahoma
Posts: 874
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Re: Rear End Posi Help!
Good info! Thanks Fitz.
__________________
1971 C/10 SWB, 15x8 Rallys, 4.5" X 7" static drop, C-notched, 350/350, 3.73 Posi. .........A 383 and Gear Vendors are on my bucket list. 1972 GMC 4X4 K1500 Survivor - Sold No matter what problems life throws at you, your time on Earth can be incredibly fulfilling and rewarding.....if you just lower your expectations. -Phil Dunphy |
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