[mn65bis]

Just wondering. Yes I know you shouldn't do this but someone out there must have tried this before. Lets say you have 2 sets of GM 3.31 gears and one is chipped on the ring gear and the other has a bad pinion. You mix the sets and have a good one of each. I got to thinking how much different can they be? Would it be good enough for a drag car? I have a chip on a 3.31 ring gear and it got me thinking about the scenerio.
Thanks

 

[MEJ1990TM]

I'd think if it was a drag car you would not be running 3.31's.

From what I have read the ring gear ,and pinion, are somewhat matched to each other from the get go. I would think at the very least they would be extremeley noisy. I'm also wondering if you could get a good pattern out of mis matched gears.

 

[mr 4 speed]

If I did it,I wouldn't tell anyone about it unless it was successful.

I will say I have reused quite a few GM ring and pinions (particularly 3.31 sets)but they where always matched and I never ever had a problem.

 

[zeke67]

They are matched parts. Especially after wearing in. I'd rather run one with a slight chip then mix and match.

 

[BillyGman]

I sure would NOT do what you're thinking about. :noway: And besides that, a new ring & pinion gear set only costs $200. that's a big job and a good amount of labor just to throw a used gear set in there, and a mismatched set at that. I'm going to cause a disagreement here by saying this, however that isn't my intention. But after performing a couple ring & pinion gear swaps myself, I would not bother performing that amount of labor on a used set of gears that would only cost me $200 to get them new. JMO though. But the mixing and matching issue, is a safety issue. I just wouldn't even consider that. OK, I'll let anyone have the last word. I've stated what i wanted to coment on in this thread, so I'm done.

 

[mn65bis]

I don't have an option to try it and I don't think I ever would, but figured I'd ask just to see. I suppose A guy wouldn't want to admit to doing it anyway.

 

[engineguy]

Ring and pinion gears are matched to each other during the manufacturing process. This the reason you will find different pinion height specs on identical gear sets. I have never heard of anyone mixing the ring or pinion between different sets, but you can be pretty much assured that you will have gear noise.

 

[driveshaft-texas]

You got nothing to lose but your time.Its all junk anyway with the chipped teeth And 3.31s are not(?) available aftermarket yet.
I have a customer that SWEARS he done this and it was quiet and he does not know ***** about building rear ends

 

[tlowe]

Just a FYI. Having torn apart many a rear and pay attention to the date codes from many sets. Sometimes the date codes from ring/ pinion are months apart. Like one built in Dec of 65 and the other made jan or feb of 66.
I never mix gears.

Not saying it can't be done. Wonder how many times people do that on Ebay? I'd be pissed.
I always throw unmatched gears away. The old iron pile gets bigger all the time. Tom

 

[mn65bis]

Ring and pinion gears are matched to each other during the manufacturing process. This the reason you will find different pinion height specs on identical gear sets. I have never heard of anyone mixing the ring or pinion between different sets, but you can be pretty much assured that you will have gear noise.

I've never seen any height specs on any old GM gears.

 

[driveshaft-texas]

I've never seen any height specs on any old GM gears.

Ring and pinions were run-in with a lapping compound like the old blister stick/compound method used to do valves long ago. Hence the pinion shim being near the same thickness in all of the same series diffs....so they all started out built to the same diminsions.Still a crap shoot for the noise. Maybe the newer machines can cut to a closer tolerance .Hobbed gears display a much different pattern and tighter backlash numbers .
Not worth the time and effort to me -but if you do this ,post up results,it will be interesting to know.

 

[mrennie]

And 3.31s are not(?) available aftermarket yet.

Actually, they are. Tom's Differential's has them made in batches of 200 at a time by U.S Gear.

Just an FYI for those looking for a set.

 

[engineguy]

I've never seen any height specs on any old GM gears.

OEM rear ends are manufactured on an assembly line, using automated methods, therefore the pinion height is not marked on the pinion gear. If the OE gears need to be removed and replaced in the same housing, then the original shims should get the gears back pretty close to the proper backlash - but it would still need to be checked.
Aftermarket gear sets will have the pinion height spec engraved on the pinion. This is probably much more explanation than is necessary, considering the question posed by the original post.

 

[Schurkey]

There is a story about Colin Chapman--the founder of Lotus sports and racing cars.

In the early years, just post-WWII, he was racing home-built cars in the local hillclimbs and junior-league track races. He decided that he wanted a particular gear ratio; and the only problem is that no one offered a ring and pinion in that combination.

He took a ring gear from one ratio, and a pinion gear from another ratio. Somehow got them jammed together in the differential. Filled the differential with liquid metal polish, and drove the car on the road for fifty miles. Disassembled the rear end, replaced all the bearings...filled it up with gear lube and went racing.

I don't know how he got the different ratio gears to mesh at all. This story was written in one of the older "history of Lotus" books, I'm guessing it's true.





By comparison, simply using non-matched gears of the same ratio pales by comparison.




Depending on WHERE the chip is, I'd run the chipped gear.

 

[MrBill66Malibu]

I will admit to mismatching gears on my brothers Saginaw 4 speed. We installed a new cluster gear and drove it up the block. This thing sounded like a noisy gear drive, maybe even louder.
Turned around and drove it back. Reinstalled old cluster gear with chipped tooth, nice and quiet!!!
My advice = Don't do it

 

[MEJ1990TM]

Mixing ring and pinion gears is an entirely different animal than mixing transmission gears.

 

[BillyGman]

Mixing ring and pinion gears is an entirely different animal than mixing transmission gears.

Correct. I believe that the biggest reason for that is due to the ring & pinion gears being of a hypoid design. Hypoid gears use teeth that slide against the teeth of the mating gear. This causes friction which the speced gear oil which is used, has to guard against. As far as I know, most transmissions use either helical or straight cut gears. Most of them being helical to my knowledge.

 

[MrBill66Malibu]

Mixing ring and pinion gears is an entirely different animal than mixing transmission gears.

Correct. I believe that the biggest reason for that is due to the ring & pinion gears being of a hypoid design. Hypoid gears use teeth that slide against the teeth of the mating gear. This causes friction which the speced gear oil which is used, has to guard against. As far as I know, most transmissions use either helical or straight cut gears. Most of them being helical to my knowledge.

Learn something new everyday, thanks guys!! :beers:

 

[BillyGman]

Learn something new everyday, thanks guys!! :beers:

You're welcome Bill. There are so many things to know in this hobby, that sooner or later, we all learn something from one another. None of us are immune to an occassional lack of understanding.