[455hota]

I have spent a couple days searching the forum, but have not found the answer to my question.

I have a 66 GTO. The original rear axle is coded YH (3:55 safe T trac with standard brakes). My reference books state from 1966 to 1970, a 2 pinion cone style carrier was available, as well as a 4 pinion cone style carrier. In all the lists of rear axle codes I cannot find any reference to 2 pinion vs 4 pinion carriers.

The 1966 Tempest order form does not show any option for 2 pinion carrier vs 4 pinion carrier.

The order form does reference HD Metallic brake linings, and all the axle ratios have two difference codes one for standard brakes and one for metallic brakes. If you ordered metallic brakes did this automatically give you 4 pinion carrier?

So if you could not choose either a 2 pinion carrier or a 4 pinion carrier, then what was the decision making process at Pontiac as to whether you received a 2 pinion carrier or a 4 pinion carrier?

As a side note many years ago I picked up a spare 1966 rear axle coded YH, and it had inside a 4 pinion carrier. I still have it to this day. So this is source of my confusion / question...

Thanks in advance!!

[nytrainer]

I have no answer but i have a 68 Arlington convertible Lemans. The 350 HO 4 speed Muncie has a 4 pinion safe-t-trac (all original).
4 pinion because of engine or trans?

[geeteeohguy]

Ol' Pinion Head would know for sure, but in my experience with these cars for the past 40+ years, the 4 pinion posi rears seem to be in the cars with 3.55 -3.90-4.33 gears and a stickshift. The 3.55 rear in my '65 GTO that I had changed out to 3.36 gears is the 4 pinion unit...while the 2.56 in my automatic '67 is a 2 pinion unit. I think the split was at 3.36...but am not sure. Anybody have a 2.93-3.08-3.23 4 pinion unit?

[Kenth]

AFAIK, first model year for the 4-pinion carrier was 1967 (production started fall 1966). Also, the housing with 4-pinion carriers had a N cast on the snout and 3.36-4.33 gears. Lower numeric gears got the 2-pinion carrier.
1969 and later G-body had a medium performance 4-pinion carrier in regular cast grey iron housing (no N on snout) for 3.23 and lower numeric gears.
FWIW

[RamAirBirds]

I have a completely original 03A built 1966 GTO 389 Tri-power 4spd
It has the original "ZK" coded 3;90 axle
original 2 pinion posi, NON nodular housing.
RA

[67GTONUT]

Originally Posted by Kenth

AFAIK, first model year for the 4-pinion carrier was 1967 (production started fall 1966). Also, the housing with 4-pinion carriers had a N cast on the snout and 3.36-4.33 gears. Lower numeric gears got the 2-pinion carrier.
1969 and later G-body had a medium performance 4-pinion carrier in regular cast grey iron housing (no N on snout) for 3.23 and lower numeric gears.
FWIW

Yes..... my original 3.36 rear has the N cast on the snout