# what rear axle is this?



## shadetreegto (Jun 9, 2012)

I have a rear end with a stamp on the drivers tube of YH and a date code of G148 and build # of 8783393. it has a posi carrier with 3:55 gears. 
I was told it is a 1969 posi rear but the code doesn't show as a 69. 
I have also found 2 different codes listed in 68 (by various research postings) one of which is YH and the other is WH.
Is it a Pontiac rear? Will it fit on my 69?


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## 05GTO (Oct 6, 2004)

For 69 YH comes back as being for a Firebird with an open carrier and 355 gears, ZH would be for a positive carrier 355 on the Firebird.

GTO offered the 3.55 rear as WH (open) XH (Posi)


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## shadetreegto (Jun 9, 2012)

will this fit my 69 gto?


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## chuckha62 (Apr 5, 2010)

shadetreegto said:


> will this fit my 69 gto?


 If it is in fact a Firebird... In a word, No. At least not without modification... Your GTO is coil sprung and the Firebird is leaf sprung. The spring perches can be modified, but the housing for the Firebird may not have the mounts for the upper control arms. You'll also need to check the length from flange to flange and compare.


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## 68GTO4004Spd (Jun 19, 2008)

Not entirely true, this is a ZH code 4 pinion nodular out of a 68 with 3:55 gears, saf-t-trac. My cars build sheet says it had a ZH code 3:55 originally. Im' not sure what a YH is, but as stated, a Firebird had leaf springs instead of coils.


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## jmt455 (Mar 26, 2012)

68GTO4004Spd said:


> Not entirely true, this is a ZH code 4 pinion nodular out of a 68 with 3:55 gears, saf-t-trac. My cars build sheet says it had a ZH code 3:55 originally. Im' not sure what a YH is, but as stated, a Firebird had leaf springs instead of coils.


68GTO4004Spd: you are correct; In 1968, the ZH axle was a 68 4-pinion, 3.55 Safe-T-Trac. But there is no listing in the 68 axle charts (from the Factory Service Manual) for a YH code in 1968. The Tempest/LeMans/GTO 3.55 open carrier in 1968 was a WH code.

shadetreegto: In 1969, the only YH axle listed for any Pontiac application is the Firebird 3.55 Safe-T-Trac. There are later axles (1971 and 72) for full-size Pontics that also have the same YH code, but those axles would have date codes ending with a "0", "1" or "2".

A YH code axle with Safe-T-Trac and a G148 date code SHOULD have leaf spring mounting brackets, not coil spring perches. It should have an overall width of 60.00". If your axle has coil spring perches, it is probably a unit that has been modified in the past. 

I'd check the overall width and compare it to the dimensions in this chart:
Rear End Widths

If it's still not evident, you might want to post some pics.


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## shadetreegto (Jun 9, 2012)

*rear pictures*

here are a few pictures of the tube end showing the perches, I think.

when measuring overall width, to what points do I measure? Axle flange to flange or backing plates?
inside or outside of plates?


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## likethat (Oct 5, 2007)

Are you sure the date code ends in an 8, could it be a 3 or 6? That is a BOP rear end for sure.


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## jmt455 (Mar 26, 2012)

shadetreegto said:


> here are a few pictures of the tube end showing the perches, I think.
> 
> when measuring overall width, to what points do I measure? Axle flange to flange or backing plates?
> inside or outside of plates?


Measure from the outside of the flanges.

Do you have a 69 axle that you can use for dimensional comparisons?


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## shadetreegto (Jun 9, 2012)

*more rear pics*

here are some more pics, I swear it is an 8 but if I were to guess another I would say it is possibly a 6.
the rear on the car now was installed back in 79 when I lost a rear wheel and shaft doing 65 on the freeway. didn't know better at the time and a guy swapped i'm guessing my open 323 for a 12 bolt 2 something.
I measured from shaft flange to flange and I think it is 61"

added info I found listed in the iegto club website:


GTO Axle Identification

Overall Housing Dimensions

Size for the standard mid-year1966 and later GTO differential is as follows:

Axle flange to axle flange is 60 15/16 inches.

Backing plate to backing plate is 55 1/2 inches.

Spring perch centerline to centerline is 35 inches.

Shock mount centerline to centerline is 49 1/4 inches.

Subtract 1" from above measurements for mid-year 1966 and earlier

I now think it is a 66 rear.


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## jmt455 (Mar 26, 2012)

I believe it is a 64-67 "A" body unit (Chevelle/Tempest/Cutlass/Skylark).
If that's correct, it is about 2" narrower than your 69 should be.

IIRC, the control arm mounting ears are set at a different angle than the 68-72.
Maybe someone can pitch in with better/more info...


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## shadetreegto (Jun 9, 2012)

If the dimensions are as described in the info in the previous screen for a late 66, will that fit the 69?
I believe I saw another example of a 66 with the same casting code
9783393


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