Hello everyone,

I just bought a 3.23 ratio gear set from USA Standard Gear for my 71 8.5 10 bolt rear end. I'm goin to use it with an Eaton truetrac differential carrier to swap from my 2.56 ratio open diff.

My question is.. i red a lot about changing differentials and gears an watched some good videos. BUT.. everytime in these kind of videos and instructions, the right Pinion Depth for the new gear set is marked on the the Pinion, but on my gear set, the only markings on the Pinion are "15A069" and "0.0" and some stamped marks that tells the ratio ("13x42").

Has anyone ever used a gear set from USA Standard gear and can tell me how i could figure out the Pinion depth that i need? Maybe the "0.0" marking means "zero tolerance from OEM pinion depth"?



Heres a picture of the Pinion.

Thanks for your ideas!

Greetings from Austria!

 

USA standard is what Randy's worldwide find a over stock or blem gear in the market place.... They are economy gears at best. Will take some fun setting up also.

When I first started differential work I delt with the USA Standard which was first call 'VALUE GEAR ' HAD TO SELL A GEAR THAT IS CALLED value gear...LOL. i COMPLAIN TILL THEY CHANGED IT TO usa standard...WHICH USUALLY never HAD usa PRODUCT INSIDE...lol.

i TOLD THEM TO DO STREET GEAR AND IT WOULD HAVE BEEN BETTER. opps caps left on...lol.

So I found excel richmond gears, and other motive gear and percision gear when they went belly up year ago... and EVEN had YUKON GEARS in the Value gear box when they ran out...I was really made as I keeping both sets on the shelf for different peoples budget that IO had to pay a TON extra for the YUKON gear and your just throwing them in the VG boxes for less...???

After that they started grinding off the YG part number....NOW the YUKON gears do not even have a YG to know they are a Yukon gear. Whole business is shady these days... I do what I can with what I have.

Motive gear red box, blue box, Richmond gear, G2, it is all under the Motive gear ring and pinion umbrella...same company !

Do the best you can start with a .037 -.035 and work your pattern from there.

Jim
JD Race

 

and after your done and get it correct you'll say to yourself "now I know why people prefer 9 inch and mopar 8 3/4"

 

Thanks a lot for your answer, Jim!

this is our first home-made ring/pionion and differential swap. We tried with some grinded-out pinion bearings to set the pinion depth and and carrier shimming by trial and error till we had a good pattern (in comparison to pictures from the net and a sheet which says which pattern is good and which not) and backlash (0.005). We ended with a 0.0346 spacer under the pinion to get there.
Pattern was checked whith fully torqued carrier bearing shells and holding the differential to put some pressure on it.

now, we have another question, were using a eaton truetrac differential, which comes with some kind of "spacer" to put between the (c clip?) axle shafts. Is this spacer needed to use with the Oldsmobile/buick bolted-in axle shafts? Or can it just be not used with this kind of axle shafts?

Greetings from Austria

Yeah, My brother owns a mopar a body with 8.75 rear and im jealous about the splitable design 😃

 

BUTTON IS NOT REQUIRED FOR THE TRUE TRAC AND BOLT IN AXLES.

.005 is pretty tight on the ring and pinion with a standard 5 cut gear...2 cut gear from GM could be as tight as .001 - .003 backlash...You have to know what type of gear you have. The 3.23 pictured is a 5 cut gear from that picture. .006 - .010 I hang around .008 -.010 for a nice quiet gear. .004 - .005 I use for drag racing only Will build up heat if used on long freeway drives of more than an hour.

 

Thank you for your tips!

Know, after a few re-shimming of the carrier, we have a backlash of 0.007. I think this is good for a street car.

Here are a few pictures of the pattern, can you tell me if this pattern is good? In comparison with the typical 'pattern examples', this looks quite good for my opinion.

 

Whats a "5 cut gear" ? Whats a "2 cut gear" ?

 

open up the backlash to .009 see what it looks like. Drive side looks a bit shallow. WHAT is the shim under the pinion?

 

Older gear technology is the 5 cut gear... has the pattern your looking at in this thread...2 cut gear will be more helical on the pinion and the ring has a heavy taper from toe to heel when the gears engage the pattern will be only a small pattern diagonal across the ring gear face in the middle.
suppose to be easier on the friction and quiet etc. tight backlash too.

 

Jim, thanks for the definition. I am sorta aware of "older technology" and gear hobs.

 

Thank ypu for your answer!

The problem is, the pinion is already installed with the crush sleeve and torqued. Seems like we were a bit early with this step. We tried with grinded out bearings an thought that the pattern is ok, so we did the final installstion.

do you think this pattern is tolerable? Or will it cause a damage over some time?

If its No tolerable, for sure, there is no other way than get new bearings and crush sleeve and deinstall the pinion again!

Thank you for the tips!