[70FormulaCA]

Was A/C an option (could be ordered) when you ordered a 70 Ram Air III Formula with the M21? Or was it just with when you ordered the M13/M20 or the Turbo 400 tranny? I assume whatever the answer, it was also true for the Trans Am models???

[Lloyd-TX]

A/C could be had on any RA III Formy or T/A, regardless of transmission choice. The only limitation would be the rear gear ratio choices.

[keith k]

Originally Posted by 70FormulaCA

Was A/C an option (could be ordered) when you ordered a 70 Ram Air III Formula with the M21? Or was it just with when you ordered the M13/M20 or the Turbo 400 tranny? I assume whatever the answer, it was also true for the Trans Am models???

Speaking for 1970 only..., you could NOT get A/C with an M21. A/C was available with the TH 400, but if you wanted a 4-speed and A/C it had to be M20.

I believe this was because the steepest gear Pontiac would allow on a '70 Bird with A/C was a 3.31. And the M21 was ONLY available with a 3.73.

This was true of both Trans Ams and Formulas.

Also, A/C was not available on the RAIV Trans Ams.

[2manyT/A'S]

Originally Posted by keith k

Speaking for 1970 only..., you could NOT get A/C with an M21. A/C was available with the TH 400, but if you wanted a 4-speed and A/C it had to be M20.

I believe this was because the steepest gear Pontiac would allow on a '70 Bird with A/C was a 3.31. And the M21 was ONLY available with a 3.73.

This was true of both Trans Ams and Formulas.

Also, A/C was not available on the RAIV Trans Ams.

Definately NO A/C with M21 in 70 Birds.

As I recall, 3:73's & Heavy Duty cooling (4 core rad) were mandatory with M21's in that year.

[Lloyd-TX]

My bad!

I did have second thoughts after making my post. Thanks for correcting me, guys.

[70FormulaCA]

Originally Posted by 2manyT/A'S

Definately NO A/C with M21 in 70 Birds.

As I recall, 3:73's & Heavy Duty cooling (4 core rad) were mandatory with M21's in that year.

Could you be able to order a lower ratio than a 3:73 (say for example, a 3:90 or 4:10?) with the M21's?

Thanks all for the info.

[keith k]

Originally Posted by 70FormulaCA

Could you be able to order a lower ratio than a 3:73 (say for example, a 3:90 or 4:10?) with the M21's?

Thanks all for the info.

Not from the factory. 3.73 (COZ code on the axle tube) was the shortest available ratio in '70.

[giles]

Chalk this up in the "FWIW" column - I was bored so I decided to look up the axle application chart in the assembly manual. The application chart as of 2/24/70 lists;
- A/C available with RAIII Formula with the 3.31 axle w/M13, M20 and M40
- A/C available with RAIII TA with 3.31 axle w/ M20 and M40
- A/C was not available with the M21 or with 3.55 or 3.73 axle.

Additionally there are some interesting comments in the "revision notes"

- on 10/1/69 "L74 + C60 usage added"
- on 10/28/69 "C60 removed from L74 usage"
- on 2/24/70 "L74 + C60 usage repositioned"

(C60 = A/C)

I would hazard a guess that A/C was not available with RAIII for the first month or so of production, but after the end of February A/C became available in the configurations listed above.

[keith k]

Originally Posted by 2manyT/A'S

Definately NO A/C with M21 in 70 Birds.

As I recall, 3:73's & Heavy Duty cooling (4 core rad) were mandatory with M21's in that year.

Yep.

One interesting triviality I've noticed through the years on '70 M21 cars, though, is that the invoice ALWAYS had the charge for the radiator (RADIATOR - HD @ $14.74 SRP), but only SOMETIMES had the charge for the 3.73 axle (AXLE - PERFORM @ $10.53), even when the build sheet showed it had 3.73s (H05 373 RATIO AXL).

The Van Nuys plant seemed to have invoiced without the axle ratio charge more often than the Norwood plant, but that may just be a "sample size" deal with the cars I've come across.

[70FormulaCA]

Very interesting stuff.

So I guess all the 189 1970 Ram Air Formulas produced that year were M21s w/ 3:73 and w/o A/C! And the 190+ (not sure the exact number) M20s may or may not have A/C and the same with the 293 automatic versions. Therefore, depending on the options, an M20 or M40 maybe more rare even though they built less M21s.

Does that sound logical?

[giles]

Originally Posted by giles

Additionally there are some interesting comments in the "revision notes"

- on 10/1/69 "L74 + C60 usage added"
- on 10/28/69 "C60 removed from L74 usage"
- on 2/24/70 "L74 + C60 usage repositioned"

(C60 = A/C)

I would hazard a guess that A/C was not available with RAIII for the first month or so of production, but after the end of February A/C became available in the configurations listed above.

Well, so much for a keen eye and really cool assembly manual notes. I checked my data and have record of 5 RAIII cars built 02C or earlier with A/C. If there was one I might be convinced it was added...but 5????

[wwilder9]

Here is page 37 of my 1970 Firebird Supplement Service Manual. 400 Ram Air shows 3.55 as standard and 3.73 as performance? Is this book wrong?

[giles]

Originally Posted by wwilder9

Here is page 37 of my 1970 Firebird Supplement Service Manual. 400 Ram Air shows 3.55 as standard and 3.73 as performance? Is this book wrong?

Nope, it is correct. The axle picture is confusing because with the "400 Ram Air" motor, otherwise known as RAIII, the 3:55 was the standard ratio and 3:73 was the performance ratio WITHOUT air conditioning. When you add A/C you automatically get the 3:31 axle.

[70FormulaCA]

Originally Posted by giles

Nope, it is correct. The axle picture is confusing because with the "400 Ram Air" motor, otherwise known as RAIII, the 3:55 was the standard ratio and 3:73 was the performance ratio WITHOUT air conditioning. When you add A/C you automatically get the 3:31 axle.

So if a RAIII car had the M21, could it have come with the standard 3:55 as stated in the manual without the A/C? I did notice in the manual under the transmission column that "4 Speed Man. Close Ratio" (if I'm reading it correctly) is not marked with an "X" ... Was this the M21?

[giles]

Originally Posted by keith k

Speaking for 1970 only..., you could NOT get A/C with an M21.
And the M21 was ONLY available with a 3.73.

As Keith said, M21 was 3:73 only....

When you ordered the M21, you were required to order 3.73 axle and HD radiator.

FYI "close ratio" is the M21
"wide ratio" is the M20, even though the only difference between the two is that M20 has a lower (numerically higher) first gear. The other three ratios are the same.

[unruhjonny]

Originally Posted by keith k

Not from the factory. 3.73 (COZ code on the axle tube) was the shortest available ratio in '70.

Ok, I'm sticking my neck out here...

I thought that 3.90:1 was available as a special order rear end in the '70 Formula & TA?

I seem to recall reading a road test on the "70+" Firebird in which a RAIV TA had a 3.90 rear gear?

Please note the pictures posted earlier are of standard rear gear sets, not special order gear sets ~ and the RAIV was not in any of that literature because it was in fact a special order engine...
If my memory serves me correct, the RAIV was only hinted as being an option by seeing parts listed in the MPC ~ and the blank spot on the engine options list.

Like I said... I'm sticking my neck out here.