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1967 Calais - Differential

Started by John Baker #2259, August 26, 2007, 12:16:34 PM

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John Baker #2259

It is my understanding that the standard differential offered on a 1967 Calais had a 2.94:1 gear ratio. However, an optional differential was offered on this car that had a 3.21:1 gear ratio.

1. I need help in understanding how/where on my car it is indicated which of the two differentials I have.

also

2. If I have the 2.94:1 gear ratio differential and want to swap out to the 3.21:1 gear ratio differential, what other (if any) part changes do I need to consider?

Are there other differential changes that you could suggest for this car? I am looking for a little more "push" on the lower end.

Any help that the collective brain trust out there could offer would be appreciated.

I recently installed a flow master muffler and stiffened the ride a bit with monroe air shocks on the back (recommended sensa track on the front), and enjoy driving this car more that ever.

Regards,

John Baker 2259





35-709

#1
All passenger car Cadillacs (i.e. other than the commercial chassis) came with the same ratios.  If the car came with AC, you most likely have the 3.21:1 rear end already, doesn't matter what model.  Although they could be special ordered with AC and the 2.94:1 ratio.  Non AC cars came with the 2.94:1, but again, in reverse, the 3.21:1 could be special ordered for the non AC cars.  I doubt that the optional axle ratios were special ordered very often, so if you have an AC or non AC car you should readily know what ratio you have.  I replaced a 3.36:1 (out of a commercial chassis) with a 2.94:1 looking for better economy on a '66 Cadillac powered '41 resto-rod (oooops) some years ago just by swapping out the pumpkins (already had plenty of power for me), not the whole rear axle.  Get the tranny speedo gear from the donor car too if you make the swap.

My 1965 Shop Manual (gotta love those shop manuals!!) says the following ..... "The gear ratio of the rear axle assembly on 1965 Cadillac cars can be determined by an identification number stamped on the front face of the carrier assembly at the end of the oil return passage.
In the case of a Controlled Differential, the letter 'G' precedes the axle ratio number.  For example: 'G2' is a controlled differential with a gear ratio of 2.94:1 ....."

Ratio .... 2.94:1   I.D. #2 
             3.21:1   I.D. #1
           
Again in 1965, the commercial chassis had available ratios of ....
             3.36:1    I.D. #6
             3.77:1    I.D. #7

Might be the same or similar for your 1967 ---- you REALLY should have the Shop Manual, relatively easy to find.  If you really want a kick in the pants get a 3.36:1 or even a 3.77:1 (if you can find one) from a commercial chassis.
8)

 
1935 Cadillac Sedan resto-mod "Big Red"
1973 Cadillac Caribou - Sold - but still in the family
1950 Jaguar Mark V Saloon resto-mod - Sold
1942 Cadillac 6269 - Sold
1968 Pontiac Bonneville Convertible - Sold
1950 Packard 2dr. Club Sedan
1935 Glenn Pray - Auburn Boattail Speedster, Gen. 2

John Baker

Hi Geoff,
Thanks for the informative e-mail. My Calais does have AC, so it appears that I most likely have the 3.21:1. Thanks for the other diff options as well.

Would you have any carb suggestions for my car, or would you stand pat with the stock quadra jet?

Thanks again,

Regards,

John Baker

Stampie

I would check and make sure your switch pitch trans is working right.  My old 67 vert could get up and go off the line.  I even beat a newer Audi A6 in a red light to red light test.

Stampie
If... the machine of government... is of such a nature that it requires you to be the agent of injustice to another, then, I say, break the law.  ~Henry David Thoreau, On the Duty of Civil Disobediance, 1849

If we desire respect for the law, we must first make the law respectable.  ~Louis D. Brandeis

John Baker

Hi Michael,

Thanks for the tip. I was hoping that you would weigh in on the discussion. Could you help me understand what the switch pitch trans is/does, and how to check it?

Beat an A6 did you? Hm, I am not getting that kind of low end performance. Any shifting involved  from lower gears up to "D" ?

Hopefully, I will get there.

Regards,

John Baker

Stampie

A switch pitch trans has variable vanes in the converter than gives you a high and low stall.  So off the line you get a high stall for performance but still keep your low stall for cruise mpg.  It's the best of both worlds.  I don't have the shop manual for 67 anymore but it should explain the functions and how to check it out.

Stampie

PS - All I did was stomp it in D.
If... the machine of government... is of such a nature that it requires you to be the agent of injustice to another, then, I say, break the law.  ~Henry David Thoreau, On the Duty of Civil Disobediance, 1849

If we desire respect for the law, we must first make the law respectable.  ~Louis D. Brandeis

Stampie

O yea you should be able to id your rear end from the number on it.  The shop manual explains what numbers mean what and if you see a tin tag on one of the bolts then you have a controlled differential.

Stampie
If... the machine of government... is of such a nature that it requires you to be the agent of injustice to another, then, I say, break the law.  ~Henry David Thoreau, On the Duty of Civil Disobediance, 1849

If we desire respect for the law, we must first make the law respectable.  ~Louis D. Brandeis

Stampie

Ok now you got me going but ... I know how much the later 472's respond to basic tuning like timing.  Are you still running stock set up on all that?

Stampie
If... the machine of government... is of such a nature that it requires you to be the agent of injustice to another, then, I say, break the law.  ~Henry David Thoreau, On the Duty of Civil Disobediance, 1849

If we desire respect for the law, we must first make the law respectable.  ~Louis D. Brandeis

Chris McBride

Sir,

the 'net is replete with more info than you would probably care to absorb concerning the "switch pitch" feature of your vintage TH400.

See, e.g.,

http://www.california.com/~eagle/SWITCH.html

http://www.google.com/search?hl=en&q=th400+switch+pitch&btnG=Google+Search

I don't have a car of your vintage but my recollection (or speculation) is that your s/p is operated by a solenoid activated from a switch on the carburetor linkage

HTH

Chris




John Baker

Thanks guys,
I have been combing the net and have skimmed a few articles and have a better understanding of what Stampie was talking about.
Chris, thanks for the links and I will check them out. I have printed an article out of Street Rodder that was informative as well.

Stampie,

My Calais has the standard/stock everything at this point in time: 429/quadrajet carb/points ignition system.
In just the last week however, I have observed dieseling after the ignition switch is turned to the off position. I will address the issue of timing/tune up before getting involved more complex measures.

Would you care to opine on the advantages/disadvantages of the various electronic ignition kits on the market (Accel, Pertonix, etc). Have you had personal experience with these products?

Last but not least, I will get "Baby Doll" up on the rack for a good look/see of the transmission.

Once again, thanks guys.

Regards,

John Baker






Stampie

Had to think there for a min.  On the dieseling check your idle speed first.  Just about every Cadillac I've owned from this era was set to high "by ear."  Set your idle to factory specs then mess with timing. 

I wouldn't throw money at it till you get the base line tune the best you can.  Too many people throw money at simple problems.  Reminds me of my old harley that the PO spent over 1g trying to fix the electric start.  When I got to looking at it, all I did was add a $3 ground wire from the starter to the battery.  Started every time after that.

Stampie
If... the machine of government... is of such a nature that it requires you to be the agent of injustice to another, then, I say, break the law.  ~Henry David Thoreau, On the Duty of Civil Disobediance, 1849

If we desire respect for the law, we must first make the law respectable.  ~Louis D. Brandeis

john baker

Will do.
Hopefully as early as tomorrow.

Regards,
John

Chris McBride

QuoteWould you care to opine on the advantages/disadvantages of the various electronic ignition kits on the market (Accel, Pertonix, etc). Have you had personal experience with these products?

I can only comment on the the Pertronix ignition kit which I use in my 64 coupe de ville (which is also a 429).  It, along with an electronic choke and Accel spark plug wires, dramatically improved the starting and operation of my 135k motor.  My .02: a lot of bang for the buck.

FWIW, many members of the 63-64 Cadillac Community have also installed the Pertronix ignition kit.  My recollection is all who commented on it did so favorably.  Some of the more cautious keep an extra set of points in the trunk in case the unit should ever fail. 

HTH

Chris

John Baker

Hi Stampie,
The tuning/timing adjustment suggestion that you made worked wonders. I get significantly more low end punch now.

Thanks again guys for all of the support and interest.

Regards,

John Baker

Stampie

O o o ... we're not done yet.  Hey kid ... you want some more candy?

Stampie
If... the machine of government... is of such a nature that it requires you to be the agent of injustice to another, then, I say, break the law.  ~Henry David Thoreau, On the Duty of Civil Disobediance, 1849

If we desire respect for the law, we must first make the law respectable.  ~Louis D. Brandeis

john baker

You Bet!
This kid has quite a sweet tooth!

What other suggestions do you have? I replaced the stock caddy air filter with a circular version from E/brock and "Baby Doll" really sings sweet now! All four octaves (barrels) really sing. The transformation in the driving experience from this car over the last three weeks has been astounding. A forty year old car with some attitude. Give me some more candy!

Lead on! Lead on!

Regards,

John




Stampie

Well the next step is to mess with your vacuum advance.  Get a T fitting from your local parts store and T off the line going to your transmission.  Feed that line straight into your vacuum advance.  One of two things will happen.  Either you will pick up more low end, mpg, and run cooler or your transmission will now shift very late.  If the first happens then everything is good and you got more free power.  If the second happens then your vacuum advance canister is bad and you have been missing out on a lot of power for a while.

Stampie
If... the machine of government... is of such a nature that it requires you to be the agent of injustice to another, then, I say, break the law.  ~Henry David Thoreau, On the Duty of Civil Disobediance, 1849

If we desire respect for the law, we must first make the law respectable.  ~Louis D. Brandeis

john baker

Hi Stampie,
Thanks again for the "candy". I will try that one out, and see how Baby Doll responds.

I will let you know what happens.

Regards,

John

john baker

Hi Stampie,
I have not incorporated your last suggestion into my car's set up as of yet, but have researched the vacuum advance topic a bit in order to understand it better. Please correct my assumptions or add to them if you have time.

The vacuum advance in my car currently runs off of ported vacuum. It will advance the spark as the rpm load in the engine increases (vacuum will drop). The challenge is, to find the optimal vacuum advance setting that is optimal for heavy load requiremnts (stomp it in "D") and light load requirements (crusin' down the road). So it seems that there would be a slight lag in spark advance under heavy load conditions, and a little too much spark advance, which burns more fuel than necessary during light load conditions.

So, I am asking the vacuum advance it to work for two masters, stomp it and crusin'.  The vacuum advance setting has to be a compromise between the requirements of the two "masters" (do not want detonation vs do not want to run too rich).

By "T-ing" manifold pressure from the line that goes to the transmission, to the vacuum advance, a more precise signal is sent to the vacuum advance to advance the spark with regard to engine load (stomp it or cruisin').

One question that I have Stampie is, does the manfold pressure from the "T" override, replace, or add to the ported vacuum once it iis connected to the vacuum advance?   Your thoughts........?

Regards,

John




Stampie

Replace.

Stampie

PS - Boy that was a lot of reading for a one word answer.
If... the machine of government... is of such a nature that it requires you to be the agent of injustice to another, then, I say, break the law.  ~Henry David Thoreau, On the Duty of Civil Disobediance, 1849

If we desire respect for the law, we must first make the law respectable.  ~Louis D. Brandeis