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68bird
White Buffalo
USA
62 Posts |
 Posted - 06 Feb 2010 : 1:14:37 PM
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| Hey guys, was wondering if you could tell me the rear gear ratio(s) originally installed in first gen birds. I have a 68 bird with a basically bone stock drivetrain and looking to do some upgrades to the rearend. Somebody told me these were equipped with 3.08? As of now Iam looking to keep the 8.2 10 bolt and install a posi with some gears etc. Any suggestions on axles, gears, posi would be much appreciated. thanks again fellas. Robb |
Robb Hermes |
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Phil
Great White Buffalo
3177 Posts |
Posted - 06 Feb 2010 : 1:56:28 PM
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| There were various ratios depending on equipment and options chosen. Add to that the fact that the car could have received a R&P swap or junkyard axle in the past 40+ years and you start seeing the need to personally check it. |
Bowties are for Peewee Herman |
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Christ
Crazy Horse
USA
1294 Posts |
Posted - 07 Feb 2010 : 11:15:38 AM
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quote:
Originally posted by Phil
There were various ratios depending on equipment and options chosen. Add to that the fact that the car could have received a R&P swap or junkyard axle in the past 40+ years and you start seeing the need to personally check it.
355 373 or 390 if for street use use 355. If you can find a set 3:42 |
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Phil
Great White Buffalo
3177 Posts |
Posted - 07 Feb 2010 : 11:28:33 AM
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3.42 is for the later 8.5. Also his car could have easily come with taller "hwy" gears.
Best not to trust, rather verify. |
Bowties are for Peewee Herman |
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sixt8bird
Chief Many Horses
USA
426 Posts |
Posted - 07 Feb 2010 : 12:21:41 PM
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| Alot of them came with 2:78 rear gears. Iwouldn't waste my time on the 8.2 rear end. Its the weakest rear end. Blown up a few myself. You can find an 8.5 out of any 2nd gen and have a better selection of gears, cheaper and way stronger. I pull them out of TAs as they are always posi's. I look for the 1979-1981 rears with the disc brakes. All you need to do is move the spring perches in about 1/2" and they bolt in. Stock 10 bolts will live behind an 11.5 second car for a long time. You can usually find a 2nd gen posi for around $200 with factory disc brake rears for $350 |
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Christ
Crazy Horse
USA
1294 Posts |
Posted - 07 Feb 2010 : 2:19:48 PM
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quote:
Originally posted by sixt8bird
Alot of them came with 2:78 rear gears. Iwouldn't waste my time on the 8.2 rear end. Its the weakest rear end. Blown up a few myself. You can find an 8.5 out of any 2nd gen and have a better selection of gears, cheaper and way stronger. I pull them out of TAs as they are always posi's. I look for the 1979-1981 rears with the disc brakes. All you need to do is move the spring perches in about 1/2" and they bolt in. Stock 10 bolts will live behind an 11.5 second car for a long time. You can usually find a 2nd gen posi for around $200 with factory disc brake rears for $350
8.2 are not weaker sorry. 8.5 form 79 to 80 yikes I never use a rear end from that time. My rear end in my t/a is all orignal and been down the track hundreds of times. You all been misinformed on the 8.2 period! |
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Phil
Great White Buffalo
3177 Posts |
Posted - 07 Feb 2010 : 2:25:27 PM
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| The 8.5 is stronger and superior (including through 81). |
Bowties are for Peewee Herman |
Edited by - Phil on 07 Feb 2010 6:04:50 PM |
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mike mcarthur
Pony that Jumps
USA
1298 Posts |
Posted - 07 Feb 2010 : 5:50:30 PM
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| Hey Phil, love the new tag line. I have my big hitch ball installed for my Toyota stopper. On the topic, I still have my original 8.2 under my 69 GTO and the wagon actually has a '70 8.2 in it. I did chip a few teeth once in the Goat, but it's held up well. Granted, I don't race it and of course no slicks. |
It's the stuff you learn after you know it all that's important |
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sixt8bird
Chief Many Horses
USA
426 Posts |
Posted - 07 Feb 2010 : 6:04:08 PM
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quote:
Originally posted by Christ
[quote]
8.2 are not weaker sorry. 8.5 form 79 to 80 yikes I never use a rear end from that time. My rear end in my t/a is all orignal and been down the track hundreds of times. You all been misinformed on the 8.2 period!
Now the 4 pinion 8.2 is very strong but once they ware worn out, they are done. They use cones and no clutches. I would beg to differ. 8.2s are as weak as you can get and cost way more to build. The 79-81s are still the same as the older 8.5. I blew up two 8.2 rear ends in my Convertible just doing some small 200ft burn outs with street tires. I stuck in an 8.5 , switched to a 4 sp and am endlessly doing 5,000 clutch drops without any problem. The car I race also has an 8.5 that does 11.75s and same thing. It took abuse when this was a 4 sp car and now its an auto with 3,000 stall and very sticky tires. Its living after 20+ years of abuse. Where do you get your info on 8.5s being weak especially the 79-81s?
The spider gears are the weak link in the 8.2s and parts are also hard to come by. The rear axle bearings also wear and ruin the axles. |
Edited by - sixt8bird on 07 Feb 2010 6:05:04 PM |
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Christ
Crazy Horse
USA
1294 Posts |
Posted - 07 Feb 2010 : 6:13:26 PM
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| We each have our own experience. Running high 9'80 with my 8.2 for years. Do cones wear out sure they do but little resurfacing of the back end and your back in business. I broke many 8.5 dumping clutch in my 1975 ta and 77 i had. From my experience I see it differantly. But your probably correct other wise why would gm have switched! |
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Paul
Sitting Bull
USA
121 Posts |
Posted - 08 Feb 2010 : 12:06:15 PM
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| 8.2? 8.5? what are you guys refering too? dont meen to sound stupid but im new to this. |
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Christ
Crazy Horse
USA
1294 Posts |
Posted - 08 Feb 2010 : 10:06:50 PM
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quote:
Originally posted by Paul
8.2? 8.5? what are you guys refering too? dont meen to sound stupid but im new to this.
rear ends! |
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sixt8bird
Chief Many Horses
USA
426 Posts |
Posted - 09 Feb 2010 : 01:10:13 AM
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| Ring gear size. Like ford 9", GMs 7.5" etc! |
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Mr. P-Body
Running Bear
USA
1506 Posts |
Posted - 09 Feb 2010 : 5:23:44 PM
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Robb,
And I agree AND disagree with much of what has been said here.
First, the 8.2 "BOP" is FAR superior to the Chevy 8.2. The former has REAL axle bearings and the latter has "C-locks" (how one can identify them). Scott Roberts' '68 Firebird went 10.40s on several occasions with the 8.2. It is NOT "stock". It has Moser axles and an Auburn "Pro Unit". Only the early versions had the "cone" type posi (yes, weak) and the "glass" side gears. Agreed, 4-pinion is the better "stocker". But the Auburn posi unit is superior to ALL the factory offerings of the day. I had a '69 GTO with a "clutch-type" posi (Eaton, I think). We've also learned the F-body is more "forgiving" regarding the strength of the rear than the A-body. I too, have "scattered" an 8.2 in a GTO on "launch".
I've seen 2.72, 2.92, 3.08, 3.23, 3.36, 3.55, 3.70, 3.90 and 4.33 in the Pontiacs, with a 3.42 and 3.63 also in Buicks and Olds (A-bodies). Richmond Gear has a reasonable selection of ratios for the 8.2.
The 8.5 is a "12-bolt in drag". That is, it has similar innards to the vernerable Chevy 12-bolt. Unfortunately, it DOES have C-locks (they gotta go for any serious performance). The later axles leave much to be desired as far as sheer strength is concerned. For a non-drag car, they're probably just fine. The 8.5 housing is at least 2" wider than the 8.2 "F-body" version, and is therefore not that good a choice. While you can move the perches "in", the offset the wheels require can make it a bit "squirrelly"... Of course, if your body has been "opened" or fenders "flared" for bigger tires, that may not be an issue.
For "driving" and a bit of racing, the 8.2 is fine. For a "serious effort", neither. 12-bolt or 9".
Jim
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mike mcarthur
Pony that Jumps
USA
1298 Posts |
Posted - 09 Feb 2010 : 7:53:41 PM
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| When I put the wagon back on the road I needed a gear set because I robbed the gears for the Goat. The highest gear that I could find was a 3:55 and I looked everywhere. I wanted a 3:23, or even a 3:08 but they weren't available. For me, the 3:55 is a bit much for the street. For what it's worth, we went with a Moser 12 bolt for Jr's 'Bird. They start at about 2K but we ended up spending about 2500 because we went with 33 spline axles, Detroit locker and a few other things. I just couldn't put that Ford rear under it. |
It's the stuff you learn after you know it all that's important |
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cutlas
Tribal Scout
Canada
11 Posts |
Posted - 10 Feb 2010 : 12:32:35 AM
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The 8.5 rear end in my car is from a nova and was a straight bolt in.
It came with a 3.08 posi.
Nice economical solution for a street car. |
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sixt8bird
Chief Many Horses
USA
426 Posts |
Posted - 10 Feb 2010 : 01:35:38 AM
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quote:
Originally posted by Mr. P-Body
The 8.5 is a "12-bolt in drag". That is, it has similar innards to the vernerable Chevy 12-bolt. Unfortunately, it DOES have C-locks (they gotta go for any serious performance). The later axles leave much to be desired as far as sheer strength is concerned. For a non-drag car, they're probably just fine. The 8.5 housing is at least 2" wider than the 8.2 "F-body" version, and is therefore not that good a choice. While you can move the perches "in", the offset the wheels require can make it a bit "squirrelly"... Of course, if your body has been "opened" or fenders "flared" for bigger tires, that may not be an issue.
For "driving" and a bit of racing, the 8.2 is fine. For a "serious effort", neither. 12-bolt or 9".
Jim
Hey Jim, not sure where you come up with 2" wider unless you got one that is out of a bigger car. I have done probably 7 or 8 swaps from the 2nd Gen Trans AM to the 1st gens and I have about 1/2" wider. Thats 1/4" per side. Not enough to notice with any tires that would fit the 8.2 rear end. The spring perches on the other hand do need to me moved in about 3/4" each side. Thats only because of the wider front and rear spring mounts on the later 2nd gens. The drive shaft also needs to be shortened 1/2" but the last swap I did , I just welded in the hole on the spring perch and redrilled the hole. Didn't make any difference in ride ,handling or looks in the wheel well. So that saved alot of cost and will be the typical swap from now on. Also if you use discs, the axles cant slide out of the rear end even if the c clip fell out. I have seen the pressed on bearings come off the axle and the axle destroyed the quarter panel. So it can happed on any 8.2 or 8.5 and as far as the C clip coming off. I have yet to see that or hear of anyone losing one? I'm sure it can happen but how often? |
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sixt8bird
Chief Many Horses
USA
426 Posts |
Posted - 10 Feb 2010 : 02:02:52 AM
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quote:
Originally posted by sixt8bird
quote:
Originally posted by Mr. P-Body
The 8.5 is a "12-bolt in drag". That is, it has similar innards to the vernerable Chevy 12-bolt. Unfortunately, it DOES have C-locks (they gotta go for any serious performance). The later axles leave much to be desired as far as sheer strength is concerned. For a non-drag car, they're probably just fine. The 8.5 housing is at least 2" wider than the 8.2 "F-body" version, and is therefore not that good a choice. While you can move the perches "in", the offset the wheels require can make it a bit "squirrelly"... Of course, if your body has been "opened" or fenders "flared" for bigger tires, that may not be an issue.
For "driving" and a bit of racing, the 8.2 is fine. For a "serious effort", neither. 12-bolt or 9".
Jim
Hey Jim, not sure where you come up with 2" wider unless you got one that is out of a bigger car. I have done probably 7 or 8 swaps from the 2nd Gen Trans AM to the 1st gens and I have about 1/2" wider. Thats 1/4" per side. Not enough to notice with any tires that would fit the 8.2 rear end. The spring perches on the other hand do need to me moved in about 3/4" each side. Thats only because of the wider front and rear spring mounts on the later 2nd gens. The drive shaft also needs to be shortened 1/2" but the last swap I did , I just welded in the hole on the spring perch and redrilled the hole. Didn't make any difference in ride ,handling or looks in the wheel well. So that saved alot of cost and will be the typical swap from now on. Also if you use discs, the axles cant slide out of the rear end even if the c clip fell out. I have seen the pressed on bearings come off the axle and the axle destroyed the quarter panel. So it can happed on any 8.2 or 8.5 and as far as the C clip coming off. I have yet to see that or hear of anyone losing one? I'm sure it can happen but how often?
GM Car
122.0, 58.31,59.25 - 37 Buick Special
126.0, 58.31,59.25 - 37 Buick Century
NA,,,, 59.1, 58.8 -- 68-74 Buick Apollo
NA,,,, 59.0, 58.8 -- 78-86 Buick Century
111.0, 59.1, 59.7 -- 75 Buick Skylark
115.0, 58.5, 60.0 -- 55-57 Chevy
108.1, 58.7, 60.5 -- 67-69 Chevy Camaro (other source shows 1081/590/589)
108.1, 60.4, 61.0 -- 70 Chevy Camaro
NA,,,, 61.3, 60.5 -- 76-80 Chevy Camaro Z-28, Pontiac Trans Am TA
101.0, 60.7, 60.6 -- 86 Chevy Camaro IROC Z
101.1, 60.7, 60.7 -- 98 Chevy Camaro
112.3, 63.7, 64.1 -- 99 Chevy Camaro LS, LT
112.3, 63.7, 63.7 -- 99 Chevy Camaro SS
119.0, 62.5, 62.4 -- 65-70 Chevy Caprice
121.5, NA,,, NA,, -- 71-76 Chevy Caprice coupe/sedan
125.0, NA,,, NA,, -- 71-76 Chevy Caprice station wagon
116.0, NA,,, NA,, -- 77-90 Chevy Caprice
115.9, 61.8, 60.7 -- 91-96 Chevy Caprice
102.0, NA,,, NA,, -- 54 Chevy Corvette
NA,,,, 58.7, 59.5 -- 68-83 Chevy Corvette
NA,,,, 59.6, 60.4 -- 84-95 Chevy Corvette
108.0, 58.5, 58.8 -- 78-88 Chevy Monte Carlo, Malibu, El Camino(117.1 wheelbase), Olds Cutlass, Pontiac Grand Prix
NA,,,, 59.8, 59.6 -- 68-74 Chevy Nova
097.0, 54.7, 53.6 -- 71-77 Chevy Vega, 73-77 Pontiac Astre, 75-80 Chevy Monza, Buick Skyhawk, Olds Starfire, 76-80 Pontiac Sunbird
NA,,,, 58.9, 59.0 -- 78-86 Pontiac Grand Prix
115.0, NA,,, NA,, -- 66 Pontiac GTO
NA,,,, 59.9, 59.6 -- 68-74 Pontiac GTO
112.25, 57.5, 59.0 -- 39 Chevy knee action
112.25, 56.375, 59.0 -- 39 Chevy I beam
116.0, 57.6, 60.0 -- 42-48 Chevy
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Mr. P-Body
Running Bear
USA
1506 Posts |
Posted - 10 Feb 2010 : 08:27:58 AM
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Not sure what your chart means, but if the 2nd set of numbers is the width, the '76-'80 IS 2.5" wider (where you high-lighted) and '70-'75 is conspicuous by its absence. I don't have an early one here, but I do have a later ne. I'll measure it to see where it "falls" in the chart.
Jim |
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sixt8bird
Chief Many Horses
USA
426 Posts |
Posted - 10 Feb 2010 : 11:36:23 AM
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| Last set of numbers is width of rear end. |
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sixt8bird
Chief Many Horses
USA
426 Posts |
Posted - 10 Feb 2010 : 11:40:50 AM
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| I installed a 1973 Formula rear end in my 1968 convertible and the width is so close you cannot tell. I did try google searching widths but the charts are all over the board. I guess the only way to truly tell is by measuring the rear ends side by side. I just thew away a couple first gen open ends but still have an HO 1968 3:36 rear end and a 1980 disc brake rear end I'll have to measure. |
Edited by - sixt8bird on 10 Feb 2010 11:45:42 AM |
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Phil
Great White Buffalo
3177 Posts |
Posted - 10 Feb 2010 : 9:07:09 PM
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| My initial take is (1) Wheelbase, (2) Front Track and (3) Rear Track. However, I'm thinking the front and rear track columns may have been reversed? |
Bowties are for Peewee Herman |
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68bird
White Buffalo
USA
62 Posts |
Posted - 01 Mar 2010 : 3:04:52 PM
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| Thanks a ton guys, I learned a ton. Guess I'll start looking for an 8.5 and start from there. |
Robb Hermes |
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68bird
White Buffalo
USA
62 Posts |
Posted - 04 Mar 2010 : 6:24:11 PM
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| Hey guys, found a few possible canidate rears. Some GM 8.5 unknowns out in the snow for $25 each. Or also a 3:73 open rear $75, a 2:56 posi rear $150, both 2nd gens, or a 3:23 posi from a 71 h/o TA for around $500. What do you guys think? Iam thinking of the $150 2:56 and upgrading the gears. If I go that route, what else should be done to it? Remember Iam a newbie at this rearend jazz. Thanks again. |
Robb Hermes |
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Phil
Great White Buffalo
3177 Posts |
Posted - 04 Mar 2010 : 10:17:46 PM
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The 2.56 will need an inexpensive ring gear spacer in order to use 2.73-up gears, fyi. Unless you can find some hybrid gears which contains a thicker ring gear, but I don't know if they are still around.
Assuming all are in good, equal condition, I would grab the 3.23 as you should be ahead of the game unless you are comfortable setting up your own gears. |
Bowties are for Peewee Herman |
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68bird
White Buffalo
USA
62 Posts |
Posted - 05 Mar 2010 : 3:18:26 PM
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| Thanks Phil. How does the price of the 3.23 sound? Fair? |
Robb Hermes |
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Phil
Great White Buffalo
3177 Posts |
Posted - 05 Mar 2010 : 5:51:43 PM
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| A bit on the high side (or is "optimistic" a better term?) and unless you can verify without a doubt that it is a good, solid unit I wouldn't touch it. But IF it IS a good solid unit, economically it appears to be a better buy. I have a 50/50 score with used rears so I just build from scratch these days. |
Bowties are for Peewee Herman |
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Firebird rear ratio??
