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Author Topic: Anybody have exploded view of BOP 10 bolt rear end?  (Read 3494 times)
81 Formula
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« on: February 02, 2012, 05:18:03 PM »

Picked up a 10 bolt posi  cheap to swap into car.  8.2 it appears.  Upon getting in to it it appears to be a Pontiac rear end and looks like somebody reversed one of the seals in it.   Anybody have exploded diagram of one?  Would like to know which current seal is in the correct way before I put new ones in!  Smile

Also,  do you know if a 10 bolt chevy has the same drum brake mounts as the 10 bolt BOP?   I have not climbed under the car to check exact measurements yet.  Guy i bought the rear end from said it came out of a 79 T/A.  But he also said it was a 3.08 gear and when I checked the numbers on the gears its a 3.23.   Looks like it shoudl match up to the car with no mods,  but if anybody has info it would be appreciated.

Learning something new everyday in this rebuild!
« Last Edit: February 02, 2012, 07:28:04 PM by 81 Formula » Logged

400 4-speed, 3.42 posi, performer rpm, hedman headers, comp cam, 6x heads.
Owned it since 1985, 2nd owner,, bought it with 23,000 miles on it.  Original engine and trans in storage.
tajoe
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« Reply #1 on: February 02, 2012, 08:14:30 PM »

If it was in a 79 F/B, then it's an 8.5, not a 8.2. (1st gen). The camaro rear brakes are the same as the F/B. As for the seal replacement, which one are you talking about? The axle seals, or the pinion seal?
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"You can sell an old man a young mans car,
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firebirdparts
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firebirdparts
« Reply #2 on: February 02, 2012, 09:45:05 PM »

I never had a reason to check, but I would be surprised if the brakes wouldn't interchange between all the axles you mention.
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Joe Bays
81 Formula
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« Reply #3 on: February 03, 2012, 07:02:57 AM »

Thanks for the info.  Figured I have no idea how long this rear end has been sitting, so while its sitting in my garage floor was going to replace all the seals.  The axle seals are the ones that one is installed different from the other.

Idea was to just swap my entire drum assemblies to the new rear end.  Thats why I am looking for a detailed diagram of the BOP rear end to compare to a chevy 10 bolt to make sure it would match up.   Other than that the gears and carrier look good in the rear end, just needs a clean up.

As far as mounting does anybody know of any issues between the two that would affect the mounts on the car?  ie wider, narrower, etc?
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400 4-speed, 3.42 posi, performer rpm, hedman headers, comp cam, 6x heads.
Owned it since 1985, 2nd owner,, bought it with 23,000 miles on it.  Original engine and trans in storage.
tajoe
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« Reply #4 on: February 03, 2012, 04:49:17 PM »

If your current brakes are OK in your 81, just remove the c-clips and pull out the axles. No need to take your brakes off the backing plates. Just remove the 4 bolts ea side where the plates bolt to the flange, and your old rear will slide out with minor tweeking on your old brakes to gain clearance. Careful of your brake lines to the wheel cylinders. I like to run some wire from the plates to the upper shock area, to hold the brakes in position, as the new rear goes in. As for the mounting, all 2nd gen F-body 10 bolts are interchangeable. You may have to connect your new companion flange to your driveshaft, with one of those adaptable universal joints, if they're different. Someone on one of these sites said they put a 1st gen rear, under their 2nd gen car, with little mods, but I thought the mounts weren't the same. Can't confirm this. Good luck with your swap.
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"You can sell an old man a young mans car,
but you can't sell a young man an old mans car"
                                       Bunkie Knudsen
81 Formula
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« Reply #5 on: February 03, 2012, 07:37:36 PM »

Thanks,  yeah need to check the date codes on the rear end.  was at parts store this evening,  finding seals for it was a task,  had to order them and still not sure.  Problem was their search database runs by make and model instead of actual rear end. 

The numbers off the old seal I pulled out and took to the store cross referenced to a 69 firebird.  Guy i bought it from said it came out of a 79 T/A.   However it looks like it may have been IN a 79 T/A,  but may not have originated there. 

Its an odd set up compared to a chevy 10 bolt.  No c clips holding in the axles,  this concerned me till I found reference to it on the web and BOP rear end axles were held in place by the end caps.

Still would love to find a diagram of that rear end,  the set up is backwards from other 10 bolts,  meaning starting from the wheel hub and working in you have end cap/brake mount, wheel bearing, bearing lock bushing/backer whatever they call it, then the oil seal. The seal is the component closest to the differential.
Looks like there should be some kind of dust shield/grommet between the end cap plate and the bearing.  Kinda looks like it has a dimple for a rubber dust grommet in there but can not find reference to it anywhere.

Closest diagram to this rear end i have been able to find is the Ford 9 inch rear end.  Both seem to have very similar set up.  Though the ford shows some kind of dust grommet as mentiond

Just trying to make sure this thing has all the parts it needs.  Hard to say what has been left out over 30 or 40 years of servicing.
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400 4-speed, 3.42 posi, performer rpm, hedman headers, comp cam, 6x heads.
Owned it since 1985, 2nd owner,, bought it with 23,000 miles on it.  Original engine and trans in storage.
firebirdparts
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firebirdparts
« Reply #6 on: February 03, 2012, 10:02:25 PM »

Well, I don't have any trouble believing it's a Pontiac axle, based on your description.  However, it should have an outboard seal.  That ball bearing should be running in the gear oil.  You cant' lubricate bearings with dirt.
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Joe Bays
81 Formula
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« Reply #7 on: February 03, 2012, 11:47:11 PM »

Well, I don't have any trouble believing it's a Pontiac axle, based on your description.  However, it should have an outboard seal.  That ball bearing should be running in the gear oil.  You cant' lubricate bearings with dirt.

Yeah no lie.   Looks like whatever yahoo serviced this thing last time just invented how he wanted to put it back together.

I did find a diagram finally, and it should indeed be as we thought and have the seal on the outside.  I am guessing that it has the wrong bearings on it as well since the ones on there I dont think will seat all the way in like they are supposed to.  I will service it and put it back together as it should be.  The tubes don't look torn up but will have to check tolerances when I am done to see.

At worst I can get almost what I paid for it in scrap metal price!  Smile
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400 4-speed, 3.42 posi, performer rpm, hedman headers, comp cam, 6x heads.
Owned it since 1985, 2nd owner,, bought it with 23,000 miles on it.  Original engine and trans in storage.
Grand73Am
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« Reply #8 on: February 03, 2012, 11:49:11 PM »

The order of the parts, outside in, would be outer retainer plate, oil seal, bearing, inner bearing retainer ring. To replace the oil seal, you have to use a press with a bearing separater tool to press the bearing off of the axle. But first, the inner bearing retainer ring has to be removed by laying the axle on a vice with the retainer bushing resting on the jaws. Then strike the bearing retainer ring with a heavy chisel in 2 places. Do not cut through the retainer ring or hit the axle surface. The 2 chisel strikes on the ring should stretch it enough to allow it to come loose and slide off the axle. Then you put the axle and bearing separater plate on the press to press the bearing off. Since you're having to remove the bearing to replace the oil seal, you may as well install a new bearing while you're at it. The new bearing must be pressed back on too. So, if you don't have those tools, and most people won't, you will probably need to take your axles to an auto machine shop to do it for you.
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Steve F.
tajoe
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« Reply #9 on: February 04, 2012, 09:59:57 AM »

So are you guys confirming that a 69 10 bolt from a 1st gen f-body, has the same leaf spring/shock mount pad dimensions as a 2nd gen? Without modifications?
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"You can sell an old man a young mans car,
but you can't sell a young man an old mans car"
                                       Bunkie Knudsen
Grand73Am
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« Reply #10 on: February 04, 2012, 01:01:25 PM »

I don't know whether the spring pad locations are the same, but I doubt it.

I forgot to mention before that I wouldn't use that rearend, so I wouldn't spend any money on it. The 8.2 is not as strong as the 2nd gen's 8.5. And I know that the 1st gen f-body rearend is not as wide as the 2nd gen. 1st gen should be about 60" from wheel mount surfaces, whereas 2nd gen is about 61-1/2".

If that 1st gen rearend were a 12 bolt, it would be very desirable, but not the 8.2.
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Steve F.
81 Formula
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« Reply #11 on: February 04, 2012, 01:39:30 PM »

Yeah decided not to go with it.  On plus side i got it really cheap and scrap metal price will about cover it!   Live and learn.   The mount pads are much closer in than the 2nd gens.

Back on the hunt for one to get rid of my 2.56 open.    Hard to come by in this area.   

Should be no issues with just getting a 3 series posi carrier and 3.23 gears and swapping it onto my existing differential case is there?

New to the rear end world sorry for the questions.
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400 4-speed, 3.42 posi, performer rpm, hedman headers, comp cam, 6x heads.
Owned it since 1985, 2nd owner,, bought it with 23,000 miles on it.  Original engine and trans in storage.
tajoe
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Posts: 3581



« Reply #12 on: February 04, 2012, 03:09:00 PM »

I agree with Steve. If it is a 1st gen 10 bolt, It's not worth modifying to fit your 81. So I'm guessing the previous owner was full of it when he told you it came out of a 79? And the other individual that posted (somewhere else, not this thread),that he put a 1st gen into a 2nd gen without mods to the spring pads is also full of it. I've had both cars, (69 and 2nd gens), and never even attempted to swap cause was always under the impression they're not compatible. Never bothered to measure, cause of what the "scriptures" in history have reported.Hopefully you'll find another rear for your car. 2nd gens are relatively available used for decent prices, if you look hard enuff.
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"You can sell an old man a young mans car,
but you can't sell a young man an old mans car"
                                       Bunkie Knudsen
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« Reply #13 on: February 04, 2012, 06:46:00 PM »

Yeah decided not to go with it.  On plus side i got it really cheap and scrap metal price will about cover it!   Live and learn.   The mount pads are much closer in than the 2nd gens.

Back on the hunt for one to get rid of my 2.56 open.    Hard to come by in this area.   

Should be no issues with just getting a 3 series posi carrier and 3.23 gears and swapping it onto my existing differential case is there?

New to the rear end world sorry for the questions.

Yes, you can keep your original axle housing and swap in a 3 series carrier with new gears in your choice of ratio. If you decide not to continue to look for a used 2nd gen posi rearend, here's a nice way to go with a new Eaton differential. Of course, you'll need the new gears too, and have a professional set it up right. So, it will be pretty expensive, but you'll know it's good: http://www.78ta.com/HTAF/index.php?topic=36299.msg378007#msg378007
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Steve F.
firebirdparts
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firebirdparts
« Reply #14 on: February 05, 2012, 03:47:40 AM »

If that first Gen rear is a pontiac posi, I would not scrap that.   It may be worth quite a few bucks.  They had several grades of posi units, and that's what a gto would have in it.  3.36 is the breakpoint for the slowest geared carrier, so you may have the middle flavor if it's actually a 3.23.  However, I wouldn't bet on the ratio being whatever the guy said.
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Joe Bays
81 Formula
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« Reply #15 on: February 05, 2012, 07:46:44 AM »

Originally the guy said it was a 3.08.

I checked the gears in it and did the math and it is a 3.23.

I was thinking about that very thing last night.  Going to put it up on craigs list or one of the pontiac sites and see if anybody needs one for a good deal.

Casting code is 9795105 which seems to point to late 60's,  the stamped code on the axle case is hard to read last letter but it is 309 YF or YB

YF would be from a GTO or 1st gen firebird posi.  The YB would make it an open tempest rear end from 66 to 69 or so.  But since its for sure a posi there seems a better chance it is the YF code.  Though in 40 years who knows what was swapped.  Other set marks on it is N for "nodular" from what I read and it has what appears to be j878 where a date code cast might be but 878 does not make sense as a date.   Need to look over it again to see if that first 8 might be a zero instead. 
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400 4-speed, 3.42 posi, performer rpm, hedman headers, comp cam, 6x heads.
Owned it since 1985, 2nd owner,, bought it with 23,000 miles on it.  Original engine and trans in storage.
81 Formula
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Posts: 490



Email
« Reply #16 on: February 05, 2012, 07:53:11 AM »

Yeah decided not to go with it.  On plus side i got it really cheap and scrap metal price will about cover it!   Live and learn.   The mount pads are much closer in than the 2nd gens.

Back on the hunt for one to get rid of my 2.56 open.    Hard to come by in this area.   

Should be no issues with just getting a 3 series posi carrier and 3.23 gears and swapping it onto my existing differential case is there?

New to the rear end world sorry for the questions.

Yes, you can keep your original axle housing and swap in a 3 series carrier with new gears in your choice of ratio. If you decide not to continue to look for a used 2nd gen posi rearend, here's a nice way to go with a new Eaton differential. Of course, you'll need the new gears too, and have a professional set it up right. So, it will be pretty expensive, but you'll know it's good: http://www.78ta.com/HTAF/index.php?topic=36299.msg378007#msg378007

Thanks for the info,  I know where a posi rear end is from a ws6 with disk brakes with 3.73 gears in it,  but he wants $979 for it,  disk would be nice but with all the other stuff left to do (paint, interior) even if I go with a new carrier and gears I am still getting out cheaper keeping my original rear end.  Plus I know what I have now and how it was treated since I have owned it for 27 years!  Smile
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400 4-speed, 3.42 posi, performer rpm, hedman headers, comp cam, 6x heads.
Owned it since 1985, 2nd owner,, bought it with 23,000 miles on it.  Original engine and trans in storage.
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