Diff swap to '67 442
Thread Starter
Registered User
Joined: May 2009
Posts: 294
From: Norfolk, NE
Diff swap to '67 442
I am swapping my current 3.90 open diff to a posi unit with taller gears in my '67 442. I have access to multiple diffs from '68-'71 Cutlasses. Will they bolt in with no mods? Special ratio 4 speed.
Old(s) Fart
Joined: Mar 2007
Posts: 50,768
From: Northern VA
If your 67 used the Type O axle with springs that just sit on the perches (as opposed to being retained with a bolt, yes they swap exactly. Despite what you may read about the 64-67 axles being narrower, the Olds factory parts book shows exactly the same rear axle housing part number for the Type O for 67 and 68, which means that they are the same width.
Thread Starter
Registered User
Joined: May 2009
Posts: 294
From: Norfolk, NE
Joe and Joe..thanks for the replies. I do have the Pontiac type open diff. I intend to keep it and replace it with a more cruise friendly ratio. I realize that taller gears will limit throttle response. Will I encounter any issues with control arms or springs when installing a '68 to '70 rear end?
Registered User
Joined: Jul 2006
Posts: 1,826
From: Richfield, Oh
Swap
The 1967-1972 A-body rears in the Buick Olds Pontiac era are all interchangable.
The 1967 was the last year for the LONG Upper control arms BUT that difference was in the GM chassis NOT the rear differential housing in any way.
You can swap in a chevy rear also from 1967 which will only be 1" narrower BUT will all have the same lower upper and spring mounting points shocks brakes etc are all the same....
So to answer your question. You will not encounter any differences from a 1968-1972 in your 1967 housing. ALL this is on the assumption that you have a ORIGINAL Olds rear in the car.
Exception 1971 1972 rear 10 bolt 8.5 will require drive shaft shortening (but that is all)
Hope this clearly help you and other understand the differences.
the Wider 55.25 rear actually started in 1966 GTO rears. Which is way earlier than thought. Flat spring perch I have 2-3 on the racks. Could be very late 66 to very early 67. All in all it is a bolt on spring to the flat perch which tells us it is 1966 era.
SO always physically measure and visually inspect a rear before letting someone tell you what it is.
JIm
The 1967 was the last year for the LONG Upper control arms BUT that difference was in the GM chassis NOT the rear differential housing in any way.
You can swap in a chevy rear also from 1967 which will only be 1" narrower BUT will all have the same lower upper and spring mounting points shocks brakes etc are all the same....
So to answer your question. You will not encounter any differences from a 1968-1972 in your 1967 housing. ALL this is on the assumption that you have a ORIGINAL Olds rear in the car.
Exception 1971 1972 rear 10 bolt 8.5 will require drive shaft shortening (but that is all)
Hope this clearly help you and other understand the differences.
the Wider 55.25 rear actually started in 1966 GTO rears. Which is way earlier than thought. Flat spring perch I have 2-3 on the racks. Could be very late 66 to very early 67. All in all it is a bolt on spring to the flat perch which tells us it is 1966 era.
SO always physically measure and visually inspect a rear before letting someone tell you what it is.
JIm
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