[JohnJudge]

Got a question.... I have an unusual 1970 Ram Air III, bench seat 4 speed GTO. It has a code 361 HD safe-t-track rear on the build sheet. Also has code 362 for special order axle. The rear in the car is the only thing non-original... how could I tell gear ratio from the factory? I am guessing either 3.90 or 4.33??

[Held for Ransom]

Build sheet or PHS invoicing?

[JohnJudge]

I have both.... Unfortunately, the build sheet is rough and missing that part

[Held for Ransom]

I want to say, 3.90:1.

[bigborehunter]

If you believe the u joint shaft is original, careful cleaning of it may reveal stripe daub codes. These usually contain the gear ratio as well. Have to be careful what you use to clean the u joint shaft though. Someone will chime in here with suggestions.

[JohnJudge]

Thanks for the info!

[GTO JOHN]

What was the transmission code? If it was a wide ratio M20 that would rule out 4.33 gears. Pretty sure you needed the M21 for those.

['ol Pinion head]

factory speedo adapter present?

[JohnJudge]

It is a M21 on the original build sheet

[Baron Von Zeppelin]

3.90 or 4.33 - both got the M21
3.55 was standard gear, and the break point for M20

Only the Buildsheet will tell which was ordered.
Same charge on invoice for either set.
Automatics were the only ones that got speedo adapters - and the Invoice would show a charge for the adapter.

From examples, about 90-95% of D-Port cars with Spec Axle have been 3.90
But 4.33's were just as available , just not as often chosen.
HD Radiator was requisite either way.

Which plant was it built at ?
I'll try to post a similar plant sheet that is easy to read and maybe it "might" could help make a better observation of your sheet.

[JohnJudge]

BVZ, it was built at the Baltimore plant. Yes, it does have HD radiator too.

Thanks for your help!

[muscle_collector]

Originally Posted by Baron Von Zeppelin

3.90 or 4.33 - both got the M21
3.55 was standard gear, and the break point for M20

Only the Buildsheet will tell which was ordered.
Same charge on invoice for either set.
Automatics were the only ones that got speedo adapters - and the Invoice would show a charge for the adapter.

From examples, about 90-95% of D-Port cars with Spec Axle have been 3.90
But 4.33's were just as available , just not as often chosen.
HD Radiator was requisite either way.

Which plant was it built at ?
I'll try to post a similar plant sheet that is easy to read and maybe it "might" could help make a better observation of your sheet.

why did the auto only get them??

[Baron Von Zeppelin]

Think it was due to more limited combos with their speedo gear sets.
All Auto D-Port with Spec Axle, and Auto IV (3.90 gear std) with or without Spec Axle , that i have invoices on - all show the adapter.

None of the Manual cars i have invoices on show an adapter with D-Port Spec Axle , or IV.

idunno what they did about that issue on 68 RA Auto cars.
maybe the adapter was issued - but at no-cost (?)

[Baron Von Zeppelin]

John, i'll post back in a while with one or more Bsheets from 70 Baltimore.

[Held for Ransom]

I think it had to do with the size of the drive gear fitting in the tailshaft.

[Baron Von Zeppelin]

Here's a Ram3 4spd 3.90
Ram4 Auto 3.90
Ram4 4spd 3.90

All are 70 Baltimore
Marked pertinents with Lime Green
3.90 code is X K
4.33 code is X M

Hope you have enough left in one of the areas to work with.
Holding up to a lamp with good reading glasses or magnifier can help too.

['ol Pinion head]

Originally Posted by Held for Ransom

I think it had to do with the size of the drive gear fitting in the tailshaft.

Believe HFR is correct. Need to examine drive gears from never been messed with original Muncies in front of 3.90 & 4.33 of '69 or 70 G70-14 equipped GTO's.

Believe we will find the drive gear in 4.33 car is a 6 tooth. Its been over 15 years since went down this road, but that is what I ran across. An original 3.90 equipped car ought to be a little easier to find to confirm tooth count. 7 tooth, 8 tooth?