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Discussion Starter #1
I have a '76 10 bolt and don't know what it came from. It has: part no. WLP035D stamped into offside housing tube, 11-1/4" vented discs/staggered callipers, coil sprung, C-clip axles with 13/32" thick flanges, 5" PCD and 1/2" studs, irregular cover (scalloped at 9 and 3 o'clock) with 3-1/4" bolt spacing, 1-1/4" pinion nut, 2.42:1 ratio (open), 7/16" crown wheel bolts (8.5"?), 61.5" wide - axle flange to axle flange, impression of screwed on plate with 351 cast into centre and part no. 555475 stamped into rear edge of the offside brake mounting flange. I believe is '71-'76 Buick or Olds-F85, has type "P" housing with twin converging ribs. The width is right for my 68 Camaro project, but before adapting it and ordering rebuild parts I want/need to be sure what I'm ordering and I'd rather upgrade an 8.5" (with 3.73's, posi, etc) than the smaller stock unit. Would appreciate any help. Regards, Bob
 

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I believe the twin converging ribs were characteristic of Pontiac. Also the 3.25" cover bolt spacing is indicative of a 7.5" ring gear. If I recall correctly the 'W' means Warren, Mich plant, the 'L' may indicate a limited slip rear, the 'P' is Pontiac. Or the 'LP' may indicate a gear ratio (hope others can help here). The 035 is the day of the year it was built, and the 'D' is day shift. GM had many coding systems for the differentials, and they varied in structure over the years - you would have to be sure of the year to get a correct decoding. Take the cover off the unit and read the stamping on the ring gear to get the real ratio if you haven't already done so. All of the above is from distant memory, so good luck to you.
 

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Discussion Starter #4
GM 10 bolt ID

Thanks to cucumber 1949 and 73 oldsman for replies and info on links. I've had cover off and crown is stamped 41-17 (2.42:1 ratio) GM 1176 (Nov '76) OUC (I have no idea). The quickp link suggests that '71-'76 full size cars were 5 on 5" PCD wheel stud pattern, but doesn't clarify make/model. I thought only Buick and Caddie had this stud pattern, do the '76 Olds and Pontiacs share this as well?? I'm kind of getting close to the ID, but not close enough yet (to start shelling $'s), but keep it coming folks, all help appreciated. Cheers from Down Under, Bob
 

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All '71-'76 full-size GM cars used the 5-on-5" pattern. Half-ton 2WD pickups also got the same pattern starting in '71.
 

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Discussion Starter #6
Thanks jimfulco, at 55 I'm learnin' a little bit more each day, ain't it fun! Hang on, what did I come in here for?? cheers, Bob
 

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The BOP rear is from US made vehicle, is definitely not an aussie 10bolt. So any further ID ideas appreciated. Is 62.5" disc to disc, made in 1976, has C-clip axles, 8.5 crown wheel with 7/16" LH thread bolts, irregular cover, sway bar bolted through bottom of lower trailing arms via bolted-in boxing channels. I suspect that because it's a 2.42:1 ratio carrier, It will require a spacer to fit 3.73's, is this correct?? Cheers Bob
 

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I'm trying to think of what American GM cars came with rear disc brakes in '76 or early '77. All I can come up with is maybe some kind of Cadillac.

I just looked at the Cad history site, and it said the only '76 that had rear discs was the Eldorado, which was wrong-wheel-drive, so that one's out, but in '77, the Sevilles & Fleetwoods got them. The Sevilles had leaf springs, thus no control arms, so my guess would be a '77 Fleetwood.

http://100megsfree4.com/cadillac

And yes on the spacer, or a series-3 carrier (for 2.73-up gears). GM's 3-series Posi carrier for 8.5" 28-spline is cast 410408N, in case you're looking.
 

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Discussion Starter #11
thanx M&M, I sometimes wonder "what did I deserve to do all this", or something like that. Interestingly, I've test fitted the (floating) calipers and the brackets and they bolt right up to both of the '77 (8.5) and the '68 (7.5) 10 bolt camaro housings and axles that I have. Sadly though they interfere with the stock '68 staggered shocks and the location of the caliper bleed screws will not allow them to be mounted in any other position without lots of rework. Incidentally, both brackets and calipers are identical, where the left (NS) mounts behind the axle and the right (OS) mounts in front. Also, on further inspection, the (single) pistons are huge and unlikely to work with my chosen front discs and master cyl., so I've decided to use the '77 camaro 8.5 housing and sell the BOP rear, the deeper I went the deeper it got. Thanks to all who contributed, its been an honour, the quest continues, to the next signpost and beyond! Cheers for now, Bob
 
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