[trishieldchief]

Just curious, it seems every 4 speed 69 TA RA III 4 speed car is a M20 Wide ratio, 3.55 car.

I ask, because I have never seen a true PHS documented M21 Close ratio 3.90 car?

Anyone have one?

[muscle_collector]

I don't recall ever seeing one either now that you mention it. hhhmmmm paging telli on this one.

[Tellyshavilli]

No never heard of one The papers I have show every ra3 as m20,m40 or m13 doesn't show any rear gear option .

[GregL]

Here is a simple rule of thumb most aren't aware of.
When ordering a car new, the buyer was given a choice of rear end ratios, not 4 speed close/wide ratio choices. That rear end choice determined whether they got a wide ratio 4 speed or a close ratio 4 speed. Not the other way around. The buyer didn't choose between an M20 or an M21. If they chose a differential ratio of 3.90:1 or lower (numerically higher) they got the close ratio M21. If they chose higher gearing (numerically lower) they received the wide ratio M20. Both perfectly good choices. Thus "The General" made sure an owner wouldn't be driving down the road in 4th gear at 45 miles an hour revving 4500 RPM or 70 miles an hour on the freeway in second gear revving 1800 RPM. So, technically, if you have an all numbers match car and you want to know if the car has an M20 or an M21 without disassembling anything, you could check the rear end code, get the gear ratio and have your answer.

[trishieldchief]

Originally Posted by GregL

Here is a simple rule of thumb most aren't aware of.
When ordering a car new, the buyer was given a choice of rear end ratios, not 4 speed close/wide ratio choices. That rear end choice determined whether they got a wide ratio 4 speed or a close ratio 4 speed. Not the other way around. The buyer didn't choose between an M20 or an M21. If they chose a differential ratio of 3.90:1 or lower (numerically higher) they got the close ratio M21. If they chose higher gearing (numerically lower) they received the wide ratio M20. Both perfectly good choices. Thus "The General" made sure an owner wouldn't be driving down the road in 4th gear at 45 miles an hour revving 4500 RPM or 70 miles an hour on the freeway in second gear revving 1800 RPM. So, technically, if you have an all numbers match car and you want to know if the car has an M20 or an M21 without disassembling anything, you could check the rear end code, get the gear ratio and have your answer.

Greg
I am very aware of this.

Someone must have ordered a 69 TA and wanted 3.90/4.33 deeper gears behind a RA III 4 speed car.
Just trying to to see if any were built ?

[Cammer-6]

so youre saying someone may have had a 4.33?
never seen legit one in a bird,only talk of such.
In my opinion a 4.33 wasnt needed,those skinny bias plys
just went up in smoke

[trishieldchief]

Originally Posted by Cammer-6

so youre saying someone may have had a 4.33?
never seen legit one in a bird,only talk of such.
In my opinion a 4.33 wasnt needed,those skinny bias plys
just went up in smoke

Cammer that is the point, I like deep geared musclecars.

Hope someone chimes in with a real 69 TA RA III M21 with 3.90 or 4.33 axle?

[GregL]

Originally Posted by trishieldchief

Greg
I am very aware of this.

...I was just late night blithering.

[johnta1]

A 400 Firebird had them, don't know why a TA wouldn't?

I don't find any TA's in my PHS's, have a regular 400 Bird though.

Maybe someone will have one to share with us.

[keith k]

If none of the folks (who have looked at a ton of these cars...) have seen one with a steep gear... it's probably because it wasn't available. Plenty of optional axle ratios on '69 Judges, and plenty of optional axle ratios on '70 T/As - so I'd assume some dealers/customers would have ordered them on '69 T/As had it been possible. Perhaps initially Pontiac was concerned with the resulting top speed of a steeply geared car not being consistent with the "SCCA road racer" image they wanted?

[74SDformula]

Don't know if this helps at all since it is just a Firebird 400 car. PHS is in post 66 I believe.

http://forums.maxperformanceinc.com/...d.php?t=675074

[Tim john]

According to the book "The Fabulous Firebird", 69 Trans Am's came w/ 3:55 rear gears. I do not know how accurate that statement is but that is what is in print, 1st. edition of the book (1979).

Tim john---

[The Boss]

Have you found one Rich that you're trying to authenticate?

[johnta1]

Here's the axle chart for the 69 Bird:



The yellow is for the 'standard' option 3.90 gear for the 400 HO & RAM AIR.
The blue and orange are for the 'Performance' option for the 400's (3.55 gear).

[trishieldchief]

Originally Posted by The Boss

Have you found one Rich that you're trying to authenticate?

No Chris, I have not found one, just always wondered, as you could order a regular 69 Firebird 400 HO/RA III car with 3.90 gears.

Why no M40/M21, 3.90, 69 RA III TA's ,seems like a great driveline combo to me?

[FASTASSBIRD]

Not a m20 or m21 but in the may 2011 issue of Muscle Car Review there is one of the two column shifted M40 cars that is claimed to have a 3.90 rear in it. It is a RAIV car that is claimed to be an executive ordered car. They show no actual paperwork in the article but being both a RAIV car and one of only two ordered with a Column shifted automatic, it shouldn't be to hard to authenticate for someone. Like I said not a M21 but is a 3.90 car and one of very few I know of

[The Boss]

Doesn't Bruno have a 4:33 coded 69 Bird rear? Can't imagine they would stamp one & put it in a car if it wasn't ordered! I have no idea if they ever built a TA with such a gear.

[My19GTO67]

My 69 350 HO bird has a 4 speed & 3.90 rear. I'll check my PHS to see if it list's the specific trans.

[Cammer-6]

Originally Posted by The Boss

Doesn't Bruno have a 4:33 coded 69 Bird rear? Can't imagine they would stamp one & put it in a car if it wasn't ordered! I have no idea if they ever built a TA with such a gear.

not saying that didnt happen but I have a 68 rear for a Bird and its got GTO code for 355.
As for the steep gears keep in mind trailer towing package(pretty sure that wasnt offered in a T/A)