[1971WARBIRD]

i thought the 3.73 rear was with 4 speed only?the rad support is interesting,got the right fenders,so wonder why they replaced it?

[goathead455]

Would the PHS show Performance Axle for the 3.73 gear ?

[2manyT/A'S]

According to my 1971 Pontiac Accessorizer (dated Jan 4/71) G92 Performance Axle was a chargeable option @ $10.53.

Does it show up on your 70's PHS?

As I understand it,ALL non A/C HO's got 3:42's

[goathead455]

Originally Posted by 2manyT/A'S

According to my 1971 Pontiac Accessorizer (dated Jan 4/71) G92 Performance Axle was a chargeable option @ $10.53.

Does it show up on your 70's PHS?

As I understand it,ALL non A/C HO's got 3:42's

Yes it does with a charge of $7.80

[1971455HO]

Pretty sure mines 3.42 and she has air. Looked at the axle code about twenty years ago. I would have remembered. Can't verify it right now. It's away from home.

[70RAlll]

Originally Posted by 1971455HO

Pretty sure mines 3.42 and she has air. Looked at the axle code about twenty years ago. I would have remembered. Can't verify it right now. It's away from home.

a/c cars came with a 3.08 gear

[74 SD455 Formula]

HO A/C cars came standard with 308's,but was'nt a 331 ( GTO 12 bolt ) Optional or was it a 323's ?

For the record my 72 T/A with A/C had a standard 308 posi.

[TA455HO]

Didn't 71 4-speed (which that car isn't) A/C come stock with 3.42? Automatics had the 3.08 gearing standard? I think my Van Nuys is 3.42.

[necdb3]

ta455ho,

You are correct. 4 spd HO cars were 3.42 even w/ AC, automatics had standard 3.08

[1971455HO]

This is good info fellas. Are rear axles, or rather, were rear axles stamped or otherwise identified with partial VIN's just like the trans tags? Can you verify whether you still have your original rear axle or not? Just wondering.

[TA455HO]

I don't believe there is a partial VIN on the differential, but on the passengers side tube on the front surface is a three digit code that signifies the ratio. I think there are other identifying features, too.

[2manyT/A'S]

Originally Posted by 74 SD455 Formula

HO A/C cars came standard with 308's,but was'nt a 331 ( GTO 12 bolt ) Optional or was it a 323's ?

For the record my 72 T/A with A/C had a standard 308 posi.

NO 12 bolt OR 3:31's in 1971,that was 70 1/2 W66 & WS4 only.

I'll check my 71 order guide.
The power train charts will confirm the A/C standard ratio for T/A's & HO's

I had a heavily optioned 71 T/A (auto) with A/C about 25 years ago & it definately had 3:08's

[70RAlll]

everyone is correct. the 3:31 gearing was a 12 bolt A/C gear set, the 3.08 was the auto 10 bolt and I guess the manual in 1971 got the larger gear.. I had always summised Pontiac mandated the lower (numerically) gears on a/c cars for 2 reasons. help keep the belt from flipping at highway speeds, plus the compressor probably had limits to how fast it could reliably turn.and the lower gears obviously helped...there is a chart in the assembly manual...

[OVERULD]

My 71 GTO, HO/RA/M22/AC/12-Bolt came with and still has the 3.31 gear set.

BJ

[74 SD455 Formula]

Originally Posted by OVERULD

My 71 GTO, HO/RA/M22/AC/12-Bolt came with and still has the 3.31 gear set.

BJ

Thats what I was getting at.I made the mistake by not clearifing T/A or GTO.I have a 72 GTO HO/RA/AC/Auto with a 12 open and 308's.I am putting in a 12 bolt posi with 331's and wanted to know if this would have been correct.Thanks for the info and sorry for the confussion....

[70RAlll]

Originally Posted by 74 SD455 Formula

Thats what I was getting at.I made the mistake by not clearifing T/A or GTO.I have a 72 GTO HO/RA/AC/Auto with a 12 open and 308's.I am putting in a 12 bolt posi with 331's and wanted to know if this would have been correct.Thanks for the info and sorry for the confussion....

please take this comment as my attempt with a bit of wit... but you two GTO guys are on the incorrect forum. This is a Trans Am HO forum, not the GTO side of PY's forum !!!!!!!!!!!!!!!!!! as is always the case, a little truth in every joke... BUT,Trans Ams came with 10 bolts in 1971 not the 12 bolt.. that was sort of the point in the 3.08/3.42 answers...

[74 SD455 Formula]

Let's see,
The title to this forum is 455 HO Forum.Yes it is in the 70-73 Firebird & T/A Tech section,but an HO is still an HO weather it is in a T/A,Formula,or a GTO.Next you'll be saying that the Super Duty Forum is only for Trans Am's.Can't we all just get along here and injoy what we have and to share info as well as ask questions and hope to get answer's ?

[TA455HO]

"455 HO FORUM" is just a *thread* in the 70-73 Firebird & T/A Tech Forum. 2Many just used the word FORUM in his thread title which made it look like a new Forum, but it isn't really. Sort of sneaky how he did that.

[giles]

OK, I know this is not specifically a "455HO" topic, but the past 20 or so posts here have dealt with axle ratios.
Decoding the '71 axle chart for TAs and Formulas I find the following...(and I may need new glasses after staring at this fine print!!)
To determine the axle ratio, you should first select the engine and trans, then in some cases there is a "performance axle option"

model Engine trans a/c axle

Formula 350 350 M38 both 2.73 there is a note that this was deleted effective 2/30/70
Formula 350 350 M38 both 3.08 performance axle option
Formula 350 350 M38 both 3.08 standard with altitude option (WT5)
Formula 350 350 M15 both 3.42
Formula 350 350 M20 both 3.42
Formula 400 400 M40 both 3.08
Formula 400 400 M40 both 3.42 performance axle option
Formula 400 400 M40 both 3.42 standard with altitude option (WT5)
Formula 400 400 M15 both 3.42
Formula 400 400 M15 w/o 3.73 performance axle option
Formula 400 400 M20 both 3.42
Formula 400 400 M20 w/o 3.73 performance axle option
Formula 400 400 M22 w/o 3.73
Formula 455 455 M40 with 3.08
Formula 455 455HO M40 with 3.08
Formula 455 455 M40 w/o 3.42
Formula 455 455HO M40 w/o 3.42
Formula 455 455HO M15 both 3.42
Formula 455 455HO M15 w/o 3.73 performance axle option
Formula 455 455HO M22 both 3.42
Formula 455 455HO M22 w/o 3.73 performance axle option

Trans Am 455HO M40 with 3.08
Trans Am 455HO M40 w/o 3.42
Trans Am 455HO M22 both 3.42
Trans Am 455HO M22 w/o 3.73 Performance axle option

All TAs and all 3.73 axles were limited slip. Other Formula axles would come without posi unless it was ordered.

The tab function did not space the columns properly. My note "both" means with and without A/C. "with" means with A/C, "w/o" means no A/C

[Father&Son73T/A]

Don't know if will PO anyone off or help but our 73 L-75 TA auto was ordered with a/c and a "performance axle" 3:42.........it's on the PHS..