Thoughts On This Ring Gear & Pinion
 

I just picked up these 3.07 gears to swap out my 3.73’s for a more friendly rpm range.
Can someone look at these pics and tell me what you think?

I picked them up for $150 as they were listed in “great condition”.

Thanks, Don

I dont see anything disqualifying i will just say its measurably harder to set up used gears not knowing previous backlash but doable

https://forums.maxperformanceinc.com...9&d=1731032765
Does the "2" represent pinion depth variance?

If not, getting pinion depth right will be a guessing game, which is going to make getting the mesh correct even more difficult.

I haven’t a clue about the 2 stamped on the pinion.

Photo #2 looks like the ring gear teeth are galled but I don't see corresponding look on the pinion teeth. Are those teeth as rough textured and pitted as the picture makes them look?

Here is a different section of the ring gear and a pic of the backside of the pinion.

What the hell are all the punch marks on the face of that gear?

The pinion depth is designated by a 2-digit code for that 12-bolt ranging from 40 to 50. A 45 designates a specific depth (can't remember what it is, have it written down) and numbers below subtract 0.001" per increment and digits above add 0.001" per increment. It can be stamped into the tip of the yoke end. I just checked a 3.07 12-bolt pinion and it is written (grease paint?) on the face of the gear on the bearing side and is a "45".

If it's anything like the similar marks on my Lumina camshafts, it's how they hold the part securely when performing the machining operation(s).
https://www.hbassociates.us/Lumina_Cam_Bulletin_002.JPG

https://www.hbassociates.us/Lumina_Cam_Bulletin_003.JPG

Not impressed with the tooth face surface in photo#2. The wear pattern is even and covers most of the face indicating proper pinion depth setting, but the pitted surface tells me there were fluid issues from heat, contamination or probably dirt. The 2.73 that just came out of my rear end after 164,000 miles had same wear pattern, but the tooth faces had a polished finish to them.

I agree. I've had these opened up with well over 200,000 miles on them, and the gear teeth are as smooth as glass. This is with in-service rear ends on these cars (ones I've owned and customer cars). This looks like rust pitting or contamination. The teeth look rough. Can you feel the surface pits with your fingernail? Or is it just visual.

My opinion: the gears can be used, but may be a bit noisy. They are not 'junk'. You may not even hear them over the exhaust being dumped out of your Tribal Tubes from that tripower 421 you're packing. :)

No stamp on top of pinion but there is a “K8” Stamped on the body and maybe the green mark used to be the code?

It’s just Light rust

Buff that light rust with 400 grit.

In your third pic where it focuses on the snout of the pinion is where it is supposed to be stamped. If you look straight down onto the face of the gear below the gear is where mine is marked "45". I also have a 2.56 pinion from 1972 and I'll check that one to see where the number is.

I respectfully disagree. Maybe some 0000 steel wool at most. Never use sandpaper or emery cloth on a gear surface. At least I wouldn't.

My first impression is the gears were media blasted to hide defects.

Yep. Took out the rust and left the pockets.

Definitely media blasted to hide defects.

Looks like the ring gear is still dusted with blasting media.

No set of used gears should like like those ones pictured.

I missed that looking at the pics. Like a Gilbey's gin bottle....the gears are frosty looking rather than shiny.

IMO, they will work but they will probably be noisy. I don't like ANYTHING bead blasted. I've seen more ruined carbs, engine cases, valve covers, you name it. Once it gets 'frosted' there's no going back.

Waiting for Ol' Pinionhead to give the final say on these. Yeah or nay?

Installed one set of used gears in a 68 Firebird for a friend. Horrible gear whine after all that work. Learned my lesson. But once, cry once…..Spend the money get a new set of gears and don’t look back. Certain parts are just fine used, for me a ring and pinion is not one of them.

Just installed a fresh set of 3.73’s in my 71 GTO, went in well and no gear whine whatsoever, Richmond gears.

Just my .02

Could it be residue from the parts being on a shelf inside a bldg in the dirty desert air?
I got these from Frank’s Pontiac Parts. Located in Twenty Nine Palms

Agree with others concerning rough gear surface. If that’s a Chevy style 12 bolt .030 to .035 pinion shim is where I’d start. Backlash at .008. You’ll probably only achieve a decent pattern on one side with used gears.

OMG clean it up see what you have, spray it with WD40 wipe tooth faces aggressively with a rag / tooth brush to remove loose particles then spray it all down with carb cleaner

No amount of pictures on the internet with people guessing on condition error'ing on the side of caution are going to be able to tell what you will be able to see with your own eyes once cleaned

Factory / parts counter gear sets were LAPPED after milling. ( only done on high quality sets now a days) The lapping process did NOT leave a smooth surface, it is grit after all. Once lapped, they then Parkerized the set for protection.
When you set up a original set from the 60's and 70's you get a Much wider and fuller gear pattern on the teeth proving the contact amount of the gears. These days you are lucky to get a good football pattern with most replacement gear sets.

Set of used 8.5 GM 3.08 gears I recently purchased here in the classifieds, said to have about 2k miles on them.

look good, and look much newer than that 1970 set.. I just tossed 2 new "us standard" 3.08 sets due to piss poor patterns .

Hopefully they’ll be fairly quiet after setup, replacing the 2.56 open 8.2 with a 3.08 factory posi 8.5 in the near future.

I just don’t spend enough time running the freeway at 75+ enough to justify the 2.56 cogs, most of my driving is at around 50 on our main road through town and in the local canyons. I don’t think my Tri-Power 068 cam 421 really likes being below 2000 rpm 90+ percent of the time, although it does drive nice and smooth.

I’m running 1700 - 1800 at around 50 and I’m thinking at 2000 - 2100 rpm it would be more efficient and would definitely make the car more fun.

I'd run them without a second thought.

GT

3.08 is a great ratio. I measure the pinion gear thickness, so no reference number on top is fine with me.
New Posi or used?
New posi units ( Eaton style or the Corp style ) both now have Carbon Fiber clutches. That means NO Synthetic oil , NO synthetic additive.
I have seen people burn up a new posi pretty quick with "the best oil", which isnt what it needs..
Problem is Older posi that needs a set of steel clutches is $$$$ money, as much as buying a while posi carrier.
just some info if you dont know already...

It’s a factory posi in good working condition. The car is just a cruiser that’s not really driven hard with skinny 215/75/14s all around so I’ll roll the dice and run the used posi as-is.

Agreed, after trying and failing in the past with used gears, only to get nothing but howling I now only purchase new. Replicating the previous backlash is a challange.