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View Full Version : gearing, questions and advice sought



vanogre
09-30-2001, 07:56 PM
I have recently dicovered that my 69 seems to have 12 bolts holdig the differential cover on. at the risk of sounding like an idiot doe this mean i have a 12 bolt rearend?
the van started out life as a sears delivery, or repair van. it originally came with a straight 6 and a 2 speed powerslide.
i now has a 350 v8 and will (hopefully soon)
have a turbo 400 transmission. if this is a 12 bolt what can i, (if neccesary) install for posi lock traction and what gearing is most advisable. while i do do some highway travel, ime really looking for a boulevard beast type performance.

ahighdiver
09-30-2001, 10:43 PM
That's the way to count them.
That is a posi.
Ten bolts are mostly limited slip
twelve bolts are posi-track
HD

TurboVan
10-01-2001, 12:26 AM
The 400 has a really tall first gear, so you'll probably want gears in the mid-to-high threes ratio (eg.3.70:1).
Not the best for highway, but pretty good all around. --- TV

vannman67
10-01-2001, 12:09 PM
I'm afraid I have to disagree with you on this one. Usually the term 10 bolt or 12 bolt refers to the number of bolts used to fasten the ring gear to the carrier inside the rear axle housing. The fact that the diff cover has 10 or 12 bolts often confuses most peopls. Try linking to this website for more info. www.442.com/oldsfaq/ofdif.htm (http://www.442.com/oldsfaq/ofdif.htm)
Although this site is directed towards the Oldsmobile it provides some good information on how to determine whether or not you have a true 12 bolt limited slip rear end. Hope this helps

Vannman

vanogre
10-01-2001, 02:18 PM
according to the info as i read it, with an olds, there is no guarantee. generally howevere with chevy, 12 bolts on the outside means it is a 12 bolt rear end. hooray. would anyone like to speculate as to whether this guarnatees posi trac.

vanogre
10-01-2001, 02:19 PM
according to the info as i read it, with an olds, there is no guarantee. generally howevere with chevy, 12 bolts on the outside means it is a 12 bolt rear end. hooray. would anyone like to speculate as to whether this guarnatees posi trac. p.s. thanks to all of you i just love having this site to talk with people about these cool old rides.
ogre

69G20
10-01-2001, 02:58 PM
I agree with vanogre I've thought that these rears for the vans were called by the # of bolts on the cover and their being posi by a red plastic warning tag on the oil fill hole. If the tag is missing you can raise both wheels off the ground safely and in neutral of course, and when you turn one wheel the other wheel will turn the same direction if it is a posi and the opposite direction if it is ont a posi.
The question of gearing seams to come up alot, the info at the site was good but I think some graphics would help.
Love this site!
Carl

MadElf
10-01-2001, 07:35 PM
If the wheel-spin test holds true (which I've heard elsewhere only works for actual locking differential, not for limited-slip posi) then not all 12-bolt rears are posi.
This assumes, of course, that 12 bolts on the cover means 12 bolt. Of course I have a GMC, so I just don't know anymore...

I'm pretty sure I have a rearend. Maybe I should go check.

bellvan
10-01-2001, 08:49 PM
i thought the test was if you lit em up in front of the local cop station and left two equal tire marks you had posi.....and if you didnt ,you somehow got caught.....hehehe,try that one on someone you dont like : )

Vanner68
10-01-2001, 09:58 PM
Only true way to tell is to pull the cover (you should be changing the gear dope by now anyway) and look for springs in the carrier.No springs, no posi.

vanogre
10-02-2001, 02:39 PM
just checked in on the rotations of the weels
when rotating the passenger side drivers side does not move. when rotating drivers side, passenger side moves but in reverse rotation, sound plain jane?

MadElf
10-04-2001, 06:13 PM
Now that's interesting. Mine spins the other wheel the opposite way from both sides.
????

TurboVan
10-05-2001, 01:03 PM
A dragging brake on the driver's side would explain it. It's easier to turn the tranny.
As far as Posi goes, there is a heavy spring clutch in there, I doubt you could slip it by hand. So if the other wheel turns opposite, you definitely DON'T have a Posi.
Also, when checking ratios, both rear wheels must be turned together (with a helper). --- TV

pat69chevan
10-05-2001, 01:33 PM
i got that ten bolt i put in over the summer and it seems to be doing well, i hope that the 700R4 will work well with it, i hope to put a twelve bolt in later. but for now, that 2 speed PG is just fine for tooling around town, gas mileage stinks!!!!!!

later

pat