1969 Judge rear end
 

Looks as though I have a 69 Chevelle rear end manufactured by McKinnon in Canada. Cast number is 3959038, date code is 0325 and there is another number C 249, not sure what this is. 12 bolt posi unit, gear ratio unknown . McKinnon did supply axles to Pontiac I believe. Is there any possibility this could be original or just an imposter ?

If it is a 12 bolt cover, it is definitely not original as Pontiac did not put a 12 bolt rear in GTO's until 1970 and only behind the 455 cars. All 69 GTO's had 10 bolt rears originally.

Many thanks, I figured as much. Is it fairly common to find 12 bolt positrons on the Judge model?

It was a fairly common swap as it was a strait bolt in. Do you know what ratio your original rear was?

You got a 12 bolt on a 455 CID in 70 and 455 HO in 71 regardless of Judge and posi was an option on any GTO with a 12 bolt...

Ratio on the window sticker was 3.55. I think the replacement is a higher ratio and closer to 4.00 since the rpms are very busy! This is what prompted me to take a closer look at the rear end. I tried to calculate by counting the prop shaft turns to one turn of the tire, came out as two to one which is certainly not accurate! Probably because I have a posi unit and had the other tire on the ground , I think both tires have to be free to turn? So will try that, and in extremis, I will remove the differential back plate

Just a follow up, I would like to use a lower ratio number , seem to be several comments that a 3.26 is a better solution than a 3.55

For Judge 273 - are you saying that a 12 bolt was an option for GTO’s but not before 1970.

Yes, It was standard on 455 in 70 and 71 455. Posi optional.

Just throwing this out there, but with a regular posi you shouldn't be able to turn the driveshaft with one wheel on the ground. If you can it means the posi isn't working.

LPete - thanks, this is going from bad to worse! Am I correct in thinking that if both wheels are off the ground and you turn one wheel clockwise, the other wheel should turn anti clockwise? The casting number is said to be a posi unit, but maybe it isn’t - is there any other way to check without removing the cover plate. My Judge is a perfect and legit unit but this axle issue is a spoiler. Any ideas on where to find a correct axle ?

grahamp, if sourcing another rear for restoration use, it would be helpful to know if the Judge was originally ordered with Safe-T-Track, or if the original rear was a 3.55 Single track, do you want to go back that way? Listing an area of where you are located would also help.

Original '67-69 Pontiac A-body 3.55 STT rears will be built off a sealed axle bearing end usage nodular housing. Being an original nodular hsg, it will have its own model year specific casting number and will be julian dated. The common gray iron Pontiac 8.2 hsg for '69 Pontiac A-bodys which was used in singletrack & 2.56-3.23 STT builds had a different casting number housing which was alpha-numerically dated.

On your '69 cast McKinnon 12 bolt, the casting number on the hsg won't determine single track or factory posi. Have you examined the axle tube for the factory line stamping indicating factory code, assembly date? Totally agree a McKinnon 12 bolt is out of place in a '69 GTO, would however be interested in the stamped codes as ton discern whether it's original use was in a Chevelle/Elco/Malibu, or if it was factory assembled with the 3R pinion flange, non Chevy backing plates, and is coded for use in a '69 Buick Skylark.

If the differential is limited slip, and you hold the driveshaft, you shouldn't be able to turn the wheels. If it's not limited slip, yes, turning one wheel should turn the other wheel the opposite direction (as long as the driveshaft is held stationary).

Old pinion head - here are some answers. Yes, my 1969 Judge came out of the factory with a 3.55 Safety Track HD rear axle and I would like to go back there with a correct date code if possible. Car was build at Fremont in April 69
Here are the stamps on the McKinnon 12 bolt Chevelle rear end - casting number is 3959038, the assembly date is 0325K and the date code is C249. I could not find a ratio code. I now doubt this is a posi unit, will try and do the wheel rotation test later today. The axle does have a GTO posi sticker XH which fooledme for a long time! I believe the McKinnon unit has a higher ratio than 3.55, much closer to around 4.00. The Judge is in Vero Beach Florida. It is a 2- Car, looks brand new and has won many awards. The axle imposter is a shocker so I want to fix it and get as close as possible to the original. Engine is original, 4 speed Muncie has just been rebuilt and has the correct casting and date code numbers. Thanks for any assistance . Chevelle unit looks as new.

Would you mind sharing your engine number? My Fremont July car’s WS engine number is 0698374, which seems like it should be in an earlier car. I’ve wondered if they had them sitting around for awhile.

Old pinion - I am now pretty sure the McKinnon axle is not a posi but will make a final check in a couple of weeks when I get back from a trip. The ratio is about 3.90 based on the wheel turn method. Two anti clockwise turns of the driver side rear wheel equals about 3.87 turns of the drive shaft. I was very sure that this axle was a higher ratio than 3.55 which prompted me to take a closer look at the axle - surprise surprise! Many evil restorers out there!

Old Pinion - my EUN is 0549408WS, the block number is 9790071 and the date code B189. Judge build date April 69.
How do I find/purchase a rebuilt rear end for the car?!

Not sure where your located but about a month ago I seen a complete rear end from a 69 Judge. 69 casting code, xh axle code and if I remember right around a 046 date code. No idea what’s actually in it though. I was gonna buy it but decided not to as I needed a xk.

I am located in Vero Beach Florida which is 90 miles north of Palm Beach. Do you have a contact number for that 1969 Judge axle - sounds perfect. At the right price I would just buy it and have it rebuilt

I see very few 12 bolts in 69 Judges. Very few. Its not a common swap from what I see

I’ll take a look and let you know.

Frank, thank you. I will have to replace it with the correct axle

Does anyone know where I could purchase a 1969 Judge rear axle assembly, preferably a 3.55 safety ride HD unit. Willing to completely rebuild to" as new condition."

BigD400 - I will wait with baited breath, many thanks. I think I saw the ad but cannot remember where. I checked Legend Magazine but could not find it.

Have seen quite a few unrestored 69 Judges with 12bolt rear "upgrades".

Seems to me we determined years back that there was a standard single track 3.55,
STT 3.55 iron, and STT-HD 3.55 Nodular - all available in 69 Judge/GTO.

If you have STT-HD on your PHS Invoice - its the Nodular.
Housing will have a big "N" raised letter on top of pumpkin.
- when you find the correct replacement.

i think BigD400 is in Canada.

You could also put a Want To Buy listing in the Parts Wanted classified section here.

The 12bolt "should" have a stamped 2 letter code on the passenger side axle tube - on the front side. aka you would be under the car looking back towards the rear bumper.

3.73 and 4.10 were the closest factory ratios.
Not sure if a 3.90 was available from aftermarket for 12bolt - but back in the 70's it could have been at one time. idunno

Baron VZ - thanks I will post a wanted ad. Yes my window sticker says the original axle was a 3.55 STT HD so I will have to look for the N. The Chevelle 12 bolt on the car works just fine but it is obviously incorrect for this Show Car. The 3.90 ratio is my best guess based on the wheel/shaft rotation which I did today

I'm curious about this window sticker.
Genuine window sticker wouldn't list the ratio.
Genuine PHS invoice wouldn't list it either.
Only the Buildsheet would spell it out. (3.55)

It can be concluded by default it was a 3.55 , if thats what you mean to say.

Not pestering you about this.
Just inquiring - it makes the window sticker sound non-original.

Baron, you are right, only the SST HD appear on the sticker, code 361, but other PHS documentation identifies the 3.55 axle ratio under the heading of 1969 Pontiac Power Train GTO - 4 Speed data. All my PHS documentation is legit and correct

Cool
Appreciate the clarification Graham.

PHS will usually fill in the powertrain page by hand with yellow hi-lighter using info from Invoice , and known Defaults.

Was a little worried you might have an amateur hand made window sticker.
Wouldn't want that to be your only source of documentation.
Sounds like you have all the bases covered. :)

Baron, all is good ! See if you can find me a replacement axle!!

I have the cpmplete drum to drum XH rear for your car if ypu cant get the other one promised.
Pm me if interested.

Ram4King - outstanding! How much do you want for it? What is the condition and what would I need to do to bring it up to Show Car condition? Can you give me the casting number and date code. I am going away for ten days today, can I send you a deposit and deal with the rest of it after 7/20. Here is my cell phone number 772 538 7225, please call me this morning if that is convenient

Big d 400
 

Replied to your last message re Judge rear end. Fortunately I have found a 1969 Judge drum to drum axle and put a deposit on it. Thanks for all your advice and assistance, much appreciated

Judge rear end
 

Big d 400, trying to make sure I replied to your message, my last thread was addressed to you. Ram4King has made the axle available, he is in PA and a check is in the mail to him. Thanks to both of you for your help and advice
Graham Phillips

Perfect!