My buddy's '69 Malibu convert with a 350/300hp and factory A/C has a 12 bolt.

 

I had an L48, Muncie M20 with a 3.31 12 bolt non posi. Bought it from the original owner, he said it was ordered with the engine and trans but did not order the rear end.

 

I'm the second owner of an untouched L48/M38 that came factory with a 2.56 geared 12 bolt.

Jerry

 

My original 69 has a 350 255hp with the factory original 12 bolt 2:56 one legger in it.

 

I think anything 300hp and above got a 12-bolt regardless of body style or transmission. The L48 (350/300) is shown with 12-bolt unique ratios such as 3.07 and 3.31 (among others) that are NOT shown with anything with less hp.

http://chevellestuff.net/1969/power_teams.htm

 

I had a complete original 69 Chevelle LM1 255 350 4bbl car that had a 12 bolt that looked very original to the car because the car had no mods at all.

 

My 69 Malibu with original 350/300 hp has a 12 bolt/2.56 posi. All listed on the build sheet. I remember reading somewhere that the 350 255/300hp cars all got the 12 bolt. Posi was up to the customer to order. Can't seem to find that literature at the moment.

Woj

 

The 300 HP 350 Came with a 12 bolt.

 

There was talk at one time that if you ordered the F40 suspension option you also got the 12 bolt. I don't know what came of that idea.

 

The 12 bolt ring gear was considered a Heavy Duty axle. I know most consider it a performance only axle but that's true.

So any option that put stress on the drive train forced the HD axle, performance engines, trailer towing, heavy duty cooling, station wagons etc. Years ago an old guy I knew that owned the local junk yard told me to look under all the station wagons for a 12 bolt as they were often ordered with heavy duty cooling, AC, PS, PB and were used to haul heavy loads (salesman, delivery etc) and pull trailers.

Trouble is station wagons never seemed to be important and were often crushed first before many other models.

 

my 70 camino was a stocker/non SS and came with 2.73 12 bolt. It was orded with a "trailering package." Sorry, doesn't answer your question but may add a piece to the puzzle.

 

My 37K mile 1969 300 Deluxe Post Sedan, 6 cylinder has a factory 3:31 posi 12 Bolt.

Dan

 

Specifically for 1969, all 4-barrel engines came with 12-bolt rears, with any exceptions noted. That includes the regular fuel 350 255 horse (LM1) (manual transmissions or F40 only) & premium fuel 350 300 horse (L48) (all transmissions). Also any lesser engines included a 12-bolt when F40 suspension was ordered (including 230, 250, 307, 350 2-barrel L65). All B07 Police option Chevelles also included a 12-bolt rear.

The LM1 350 was dropped later in production and replaced with the L65. The L65 includeded a 10-bolt by default regardless of transmission.

Curiously, the Chevrolet specs show the 2.56:1 rear axle was 12-bolt only, meanwhile the AMA specs show the 2.56:1 & 2.73 rear axles were 10-bolt only. (Inconsistencies in Chevrolet vs. AMA documents like this are most troubling, especially when it involves emissions equipment, police & roadside inspections!)

The 2.56 ratio was an optional economy ratio available right down to the 230 six when a Turbohydramatic was ordered as long as it wasn't a wagon or having a/c.

 

Specifically for 1969, all 4-barrel engines came with 12-bolt rears, with any exceptions noted. That includes the regular fuel 350 255 horse (LM1) (manual transmissions or F40 only) & premium fuel 350 300 horse (L48) (all transmissions). Also any lesser engines included a 12-bolt when F40 suspension was ordered (including 230, 250, 307, 350 2-barrel L65). All B07 Police option Chevelles also included a 12-bolt rear.

The LM1 350 was dropped later in production and replaced with the L65. The L65 includeded a 10-bolt by default regardless of transmission.
QUOTE]
All this agrees with research I've done. Also from what I can tell the LM1 automatics got a 12 bolt too. Yes per Chevy specs all cars with F40 susp option got the 8 7/8" ring gear (12 bolt) differential. Even the std 6 cyl.

 

A local guy has a car equipped nearly identical to mine, except his being earlier he has the 255hp 350/TH350 and mine being later 250hp 350/TH350. His has the 12-bolt, and mine has the 10-bolt. Both cars have the triangulation braces.

 

Its also possible that shortages occurred and some cars got HD axle even though they normally would not have. Its one of those items where a HD can replace a standard but a standard can't replace the HD.

I don't mean an assembly line error but intentional substitution of the HD part due to temporary shortage of the standard part.

 

Very interesting information. Thanks for the input guys

 

My 69 vert with 255hp 350 has a 2.56 12 bolt. I have the original paperwork (purchase order) showing it. The car was built early, 8-68.

 

Which trans? TH350 or PG? Sounds like a TH350 ratio.

 

Forgot about the LM1 regular fuel engine and for some reason it's not listed on the 69 Power Teams chart. Looks like for 69 anything over 250hp got a 12-bolt.

 

I'm wondering now about an L65 250 hp 350 with 4 speed. 10 bolt or 12 and Muncie or Saginaw.

 

Probably redundent info, but we had a '69 250hp L65/TH350 that came with a 10-bolt non-posi 2.56.