FAQ |
Members List |
Social Groups |
Calendar |
Search |
Today's Posts |
#1
|
|||
|
|||
12 bolt question
Looking through factory specs, the 70 TA had 4 ratio choices on a automatic transmission. Is this pretty variable, or did one get the majority of the "default" factory ratio?
I am trying to see my ratio is in original documentation, but must be doing this wrong. Where is the best place to look? Rear end tag? It is totally locked. I wll be evaluating once I know what I have got. |
#2
|
|||
|
|||
12 bolt
I'm learning too. Step one I guess you'll be look at your rear end if you have it still. Should be a 12 bolt. There is a code stamped on rear passanger axel. If automatic with ac max ratio is 331 gear. The trans am got a 355 with no ac. I think performance package was 373 but not sure if automatic got that. All in theory should be posi. But over the last year I have seen one with option 307 gear and an automatic ac car with a 331 open ,so thing happen. You need to give more info of options. 2nd thing is order your phs docs but not sure if gear ratio show up. 3rd hunt for billed sheet probably under rear seats or gas tank. Funny a guty had door panels and tried to sell ne a set and tried to convince me to remove door panels to look for billed sheet. Don't do that. There is alot of knowledge hear and hope we can help you. If you got a good housing build it the way you want it and have fun. There is pic of my code for my ra3 auto formula, I didn't have posi and my phs docs say 307 or 331 . I choose 307 from 1970 chart and I.was wrong. Took me another year to correct that error. I would cross reference 71 chart with 70 chart. But it should be simple since you have ta. Hope I didn't bore or confuse you. Im.still learning too. But also learning not to overthink or over restore a car. About a year ago a ta sold for over 100k with all repop Interior from.ames. Some guys in group were upset but that goes to show you you can buy restore fast then enjoy,sell ect without breaking the bank. My 2 cents. I'm never number matching again it's a long detailed process and some never finish.
|
#3
|
||||
|
||||
The gear you want is the gear that matches your driving habits.
__________________
70 TA, 467 cid IAII, Edelbrock D-port heads, 9.94:1, Butler HR 236/242 @ .050, 520/540 lift, 112 LSA, Q-jet, TKX (2.87 1st/.81 OD), 3.31 rear https://youtube.com/shorts/gG15nb4FWeo?feature=share |
The Following 2 Users Say Thank You to jhein For This Useful Post: | ||
#4
|
|||
|
|||
Have PHS. Need a little help finding that piece of data on it. Trying to find time to get back on the mechanics of it. Too many cars broke this summer, got me buried.
|
#5
|
|||
|
|||
Doesn't it mention the ratio straight after the engine and 4-speed info? The few I just looked at for 1970 GM did. That's the PHS order form, not the buildsheet.
Also, that tells you what it came with, not what it has now. Even if you found stamped info on axle tube, it may not tell you that the diff has been swapped at some point or the internals, it's extra info though that help complete a story for the car. You may have to pull the rear cover, give it a fluid change if not done in recent years, count the teeth and confirm with the cast part numbers on the gears. That will confirm what's in it, up to you to decide if that's ideal based on how you drive, or if originality matters, if you can even confirm that detail. If the current speedo is accurate then checking the current speedo gears and current rear tyre diameter will give you a good ratio figure also, more accurate than trying to jack up and count wheel turns. But also a lot of work to confirm something a backwards way. |
The Following User Says Thank You to Trevor78 For This Useful Post: | ||
#6
|
||||
|
||||
Basically, from the factory, if it has AC it had a 3.31 gear.
If no AC it would be 3.31 with TH400 or 3.55 with M20. These would not show on PHS. M21 could be ordered and would show on PHS. If it shows Performance Axle it could have the 3.73 gear without AC.
__________________
John Wallace - johnta1 Pontiac Power RULES !!! www.wallaceracing.com Winner of Top Class at Pontiac Nationals, 2004 Cordova Winner of Quick 16 At Ames 2004 Pontiac Tripower Nats KRE's MR-1 - 1st 5 second Pontiac block ever! "Every man has a right to his own opinion, but no man has a right to be wrong in his facts." "People demand freedom of speech to make up for the freedom of thought which they avoid." – Socrates |
The Following 2 Users Say Thank You to johnta1 For This Useful Post: | ||
#7
|
||||
|
||||
Found a chart I think I have posted before from the Firebird Suppliment:
But this is another chart which shows different choices, which I think , may be closer to what I wrote before in post. (shows Trans Am and other model choices)
__________________
John Wallace - johnta1 Pontiac Power RULES !!! www.wallaceracing.com Winner of Top Class at Pontiac Nationals, 2004 Cordova Winner of Quick 16 At Ames 2004 Pontiac Tripower Nats KRE's MR-1 - 1st 5 second Pontiac block ever! "Every man has a right to his own opinion, but no man has a right to be wrong in his facts." "People demand freedom of speech to make up for the freedom of thought which they avoid." – Socrates |
The Following 2 Users Say Thank You to johnta1 For This Useful Post: | ||
#8
|
|||
|
|||
3.31 then. I am down to counting teeth. No ability to turn anything. 100% frozen up. Have drive shaft off, busted brake drums loose . But those were also seized. Car was driven like they stole it, so it's probably a scrap pile inside.
|
#9
|
|||
|
|||
The 1st chart is original from 70I think and it shows m40 auto transmission got only 307 but posi safety track could be purchased. When I was trying to figure this stuff out I swore I has 307 standard. Then a group member should me second chart. Way more detail but it's a 71 chart. Factory was confused back then and cause us to misread charts. Learn from my mistakes and ask group first. I found 2 simular cars with 331 open foe me but most likely your stamp should match a 331 posi unit if auto with ac. If your rear end is beet up just rebuilt it but before you do anything see if it's correct housing and stamped axle. If frozen up I think gears no good , I'd probably get all new stuff and wouldn't worried about what is actually in there unless you want to reuse it gear teeth might be wore out too. I'm learning all this stuff too. Hope I helped you out. I..not sure what is best for rebuilding these units but Eaton road race might be good with new axel,. Factory axel are only hardened about .50 of an inch and they wear at the bearing making them weak. I spoke with a local shop., just sharing what was told to me.
|
#10
|
||||
|
||||
Quote:
In actual production, there were only 3 ratios that would have come on a 70 TA automatic. -The standard ratio would have been 3.55. -As johnta1 noted, if it had A/C it would have come with 3.31s. I've seen one or maybe two exceptions to this over the years (factory A/C cars with 3.55s). -If it was factory ordered with the Performance Axle Ratio (which you'll see on the PHS, if it was), that would be 3.73s. Performance Axle wasn't available with A/C. If yours was originally a 3.31 car, the axle tube should be stamped with a "CO V" code.
__________________
keith k 70 Trans Am RA III / T400 / Lucerne Blue / Bright Blue 70 Trans Am RA III / M20 / Lucerne Blue / Sandalwood 70 Formula RA III / M21 / Lucerne Blue / Bright Blue |
#11
|
||||
|
||||
I think if the 3.73s were selected with the M21 trans, the HD cooling option was mandatory. That's how my 70 is set up.
__________________
"Those poor souls have made the fatal mistake of surrounding us. Now we can fire in any direction" 1970 Trans Am RAIII 4 speed 1971 Trans Am 5.3 LM7 1977 Trans Am W72 Y82 1987 Grand National |
The Following User Says Thank You to 72projectbird For This Useful Post: | ||
#12
|
||||
|
||||
Yes, exactly. A mandatory extra cost "option".
|
#13
|
||||
|
||||
Quote:
your car is a '400 Ram Air' car; that engine was never combined with 3.07; Both those charts show this.
__________________
1970 Formula 400 Carousel Red paint on Black standard interior A no-engine, no-transmission, no-wheel option car. Quite likely one of few '70 Muncie three speed Formula 400's left. 1991 Grand Am: 14.4 @ 93.7mph (DA corrected) (retired DD, stock appearing) 2009 Cobalt SS: 13.9 @ 103mph (current DD; makes something north of 300hp & 350ft/lbs) |
The Following User Says Thank You to unruhjonny For This Useful Post: | ||
Reply |
|
|