Changing Rear End Gears
Jerry Deren
looking to change the gear ratio to 3.42. I was looking at Richmond Gears
and it stated that if replacing stock 2.56 and numerically lower gears, the
carrier must be replaced with a carrier of 2.73 or higher. Does anyone know
why this must be done and how expensive this would be to do? Also, would it
be cheaper to buy a complete rear end with the gear ratio I want from a
boneyard and do it myself or is there another way accomplish this?
Thanks in advance
Jerry
j...@ssinc.com
RBreak
The 2.77 and lower numerical carriers place the ring gear in a different
position in the housing than the 3.08 and higher carriers. This is because
the 3.08 and higher gears are "thicker" than the 2.77 and lower gears.
Moving the gears keeps them in proper position relative to the pinion
gear.
Finding a complete 3.42 posi that would bolt in would be a good way to go,
but it might be hard to find. The 2.77 and lower rears are plentiful but
the 3.08 and higher are getting kind of rare, especially the posi's.
Another option is to get a new carrier, along with new gears that will
bolt into your housing. Auburn Gear makes some that will work and beef up
the strength of your rear also. They are also very good posi's. Jegs high
performance mail order sells them for around $250.00 to $275.00. Give them
a call at 1-800-345-4545 if your interested in that route. good luck.
Rob
Markus Strobl
>
> I have a 1980 T/A with a GM 10 Bolt (new style) 2.41 posi read end and I am
> looking to change the gear ratio to 3.42. I was looking at Richmond Gears
> and it stated that if replacing stock 2.56 and numerically lower gears, the
> carrier must be replaced with a carrier of 2.73 or higher. Does anyone know
> why this must be done and how expensive this would be to do?
With lower numerical ratios, the pinion gear gets bigger. This makes the ring
gear move further out. Installing a 3-series gear will not be possible, as
the ringgear will be too far to the left (drivers side). You can do one of
3 things:
1... Get a spacer. I'm not sure I like this idea. It feels as if the rearend would
be weaker. But I heard of people using them and say they're ok.
2... Get a aftermarket gear that fits a 2-series carrier but has a 3-series ratio.
Richmond may offer such a gear. Call them and ask.
3... Get a 3-series carrier. Auburn sells them and they have better posi units than
stock. They're in the $300 range.
> Also, would it
> be cheaper to buy a complete rear end with the gear ratio I want from a
> boneyard and do it myself or is there another way accomplish this?
If you find a axle with the right gear for a decent price, that would be the way to
go. Be sure to take the diff cover off and check that it looks ok before spending
money. If the oil is pitch black, buyer beware. This would also be a great time to
try and find that WS6 disc-brake rear axle...
> Thanks in advance
> Jerry
> j...@ssinc.com
--
Markus Strobl 96 Z28 6M Black/grph. Borla, !CAGS, PEG2, QLC
Dallas, Texas 1LE driveshaft, Honker, T-tops, CD, leather
F-member 9/93 13.87 @100.31 2.11 60ft ---- 27.5mpg @85mph
Markus Strobl
>
> Jerry,
>
> The 2.77 and lower numerical carriers place the ring gear in a different
> position in the housing than the 3.08 and higher carriers.
> Rob
Actually, the poster has a 80 TA and on these cars the 2.73 will also work.
2.56 and lower has the 2-series carrier. I had a '75 Camaro (same axle)
that came with a 2.73 Posi and I installed a set of 3.23s with the same
carrier, no probs.
Ed Treijs
>
>I have a 1980 T/A with a GM 10 Bolt (new style) 2.41 posi read end and I am
>looking to change the gear ratio to 3.42. I was looking at Richmond Gears
>and it stated that if replacing stock 2.56 and numerically lower gears, the
>carrier must be replaced with a carrier of 2.73 or higher. Does anyone know
>be cheaper to buy a complete rear end with the gear ratio I want from a
>boneyard and do it myself or is there another way accomplish this?
GM's differential cases came with different flange widths for two, three, and
four-series gears. A 2.41:1 pinion will be a lot wider than a 3.90:1 pinion.
If both were mounted on the same differential, then the 3.90 ring gear would
have to be extremely thick to engage the pinion.
Your best bet indeed is to find a complete axle, but 3.42:1 are rare. 3.23:1
are around; 3.08:1 and 2.41:1 are common. :-( You may want to look at Z/28
axles.
Changing the differentials can be an expensive proposition: first you have to
find one, then you've got to swap it in--lots of shimming and measuring
involved.
Ed (no simple answer) Treijs
Linton Smith
I was wondering where you got to! I was reading your stuff down in
Australia a lot. How is the firechicken. Still holding together?
Cheers
Linton Smith
'67 Camaro
Brian L. Oke
Hmmm, I've got a '75 Firebird. I think it's got a 2.89 or something. I
know it's posi. Would I have any problem in putting a set of 3.53 or so
gears?
Thanks
Markus Strobl
> Hmmm, I've got a '75 Firebird. I think it's got a 2.89 or something. I
> know it's posi. Would I have any problem in putting a set of 3.53 or so
> gears?
>
> Thanks
First make sure exactly what you have. AFAIK there is no 2.89 gear. Pop
the diff cover off and look for stampings on the ring gear. If you can't
find any stampings, you have to count the teeth on the ring and pinion.
If the ring gear has 41 teeth and the pinion has 15, you have 41/15=2.73,
for instance.
If you have 2.73s now, you can put on 3.08, 3.23, 3.42 and 3.73 gears without
changing the carrier. Some aftermarket gear manufacturers will also offer
4.10s that will fit, but the OEM GMs won't.