Help me find my Rearend - The 1947 - Present Chevrolet & GMC Truck Message Board Network

70GMuttC · 06-08-2004, 10:12 PM

I just started tearing my 1971 K10 project apart. I opened the rear diff to start cleaning it up and found it wasn't opened, but had a posi or locker of some kind. We started looking closer and found the axle perches are 2" wide (from a car?) instead of 2 1/2" and have some really bad welds on them as well as the shock mounts. But what I really need help with is the gears in the rear, a 12 bolt, but the gears are stamped with a 3/83 manufacture date. So if anyone can help...PLEASE?!?!? Oh yeah the whole gear stamp if anyone can decode it: 1 GM 339635 11 41 3 83. I'll post pictures of the posi lookin thing when I get to work tomarrow.

Thanks,
Jason

**JIMs70GMC** · 06-09-2004, 04:59 AM

Looks like 3.73 gears. Post up those pics of the differential when you get them.

70GMuttC · 06-09-2004, 11:55 AM

http://community.webshots.com/album/151012467eTZxHW

ChrisK10 · 06-09-2004, 12:41 PM

Unless you have a really really bendy neck, just use two mirrors....

:p

Lippyp · 06-09-2004, 12:45 PM

I just prefer to use my hands, can even find it in the dark that way!

LONGHAIR · 06-09-2004, 01:05 PM

I would say that the numbers (GM 339635 11 41 3 83) 11-41 are the gear ratio .......3.73 and the date 3/83 and your pics show what GM calls "Gov-Lock".
They are known to be weak with larger tires/higher horsepower.
The little springloaded "governor" allows some wheel spin/slippage before trying to stop it. The governor is supposed to only allow one wheel to rotate a certain percentage faster than the other.........but it only works below approximately 20 MPH. The mechanism works by centrifugal force and once spinning fast enough it doesn't try to lock. The idea was to be smoother than the old fashioned Posi unit..............smooth doesn't translate to heavy duty though.

70GMuttC · 06-09-2004, 01:07 PM

How weak are they known to be? I am going to run 33's and around 350 hp.

06-08-2004, 10:12 PM	#1
70GMuttC Registered User Join Date: Apr 2004 Location: Fallon, NV Posts: 28	Help me find my Rearend I just started tearing my 1971 K10 project apart. I opened the rear diff to start cleaning it up and found it wasn't opened, but had a posi or locker of some kind. We started looking closer and found the axle perches are 2" wide (from a car?) instead of 2 1/2" and have some really bad welds on them as well as the shock mounts. But what I really need help with is the gears in the rear, a 12 bolt, but the gears are stamped with a 3/83 manufacture date. So if anyone can help...PLEASE?!?!? Oh yeah the whole gear stamp if anyone can decode it: 1 GM 339635 11 41 3 83. I'll post pictures of the posi lookin thing when I get to work tomarrow. Thanks, Jason

06-09-2004, 04:59 AM	#2
JIMs70GMC user # 2756 Join Date: Jun 2001 Location: Chesapeake, Virginia Posts: 4,612	Looks like 3.73 gears. Post up those pics of the differential when you get them. __________________ 1970 K25, 8' stepside bed 350/465/205 44 up front, 60 in the rear 4.10s rolling on 33" Dunlop MTs 1986 K5, 350/465/208 Dana 60/14 bolt from a cucv 36" Super Swampers TSL/SX 1983 K20 w/ CUCV axles, 350/700R4/208 sitting on 37" Goodyears 1986 M1031 6.2 diesel, TH400/NP205 locker in the rear and a LS in the front, all stock for now..... 1986 K30, 350/400/205 dana 60 and 14 bolt. I kept the drivetrain. Body/bad and chassis are gone. 1981 K30, 350/465/205 dana 60 and dually 14 bolt. Has a G80, and a flat bed. Going to replace the flat bed. 1985 K20, 350/400/208 10 bolt and SF 14 bolt. I wonder where I can find some 1 tons. Hmmmmm

06-09-2004, 11:55 AM	#3
70GMuttC Registered User Join Date: Apr 2004 Location: Fallon, NV Posts: 28	Here are some pics http://community.webshots.com/album/151012467eTZxHW

06-09-2004, 12:41 PM	#4
ChrisK10 1971 C20 Custom Camper Join Date: Mar 2003 Location: Ames/Shenandoah, IA Posts: 1,435	Unless you have a really really bendy neck, just use two mirrors.... :p __________________ '71 Chevy C20 Custom Camper, 454, TH400 '97 GMC K1500 5.7L

06-09-2004, 12:45 PM	#5
Lippyp English Chevy Owner Join Date: May 2002 Location: Shropshire, UK/ Lot, France Posts: 1,848	I just prefer to use my hands, can even find it in the dark that way! __________________ Phil '67 C10 long fleet. 350/TH350, 4 bbl Carter, K&N, Dual exhaust, loads of stuff coming soon 2001 S10 Blazer Daily Driver, bone stock 4 door 4x4 with manual transmission

06-09-2004, 01:05 PM	#6
LONGHAIR just can't cover up my redneck Join Date: May 2004 Location: Columbus OH Posts: 11,414	I would say that the numbers (GM 339635 11 41 3 83) 11-41 are the gear ratio .......3.73 and the date 3/83 and your pics show what GM calls "Gov-Lock". They are known to be weak with larger tires/higher horsepower. The little springloaded "governor" allows some wheel spin/slippage before trying to stop it. The governor is supposed to only allow one wheel to rotate a certain percentage faster than the other.........but it only works below approximately 20 MPH. The mechanism works by centrifugal force and once spinning fast enough it doesn't try to lock. The idea was to be smoother than the old fashioned Posi unit..............smooth doesn't translate to heavy duty though.

06-09-2004, 01:07 PM	#7
70GMuttC Registered User Join Date: Apr 2004 Location: Fallon, NV Posts: 28	How weak are they known to be? I am going to run 33's and around 350 hp.



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.