'69 3.90:1 in a '71 - Pontiac GTO Forum
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post #1 of 13 (permalink) Old 01-02-2011, 11:54 PM Thread Starter
 
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'69 3.90:1 in a '71

Pretty new guy here, just got a '71 copper goat! Happy for me....I've been running the #'s on this and the engine and trans are #'s match, I even have 5 KU code rally II wheels. The rear end, however is a different story....I've read everything I can get to find in print or the internet and all I can find is this:
I have scraped, sanded and cleaned both axle tubes and there are no stampings I can find ...BUT the casting code on the left rear side is CFD 1 and on the right rear, casting code is 9795084, with a cast 233 above those numbers. I think I read a thread here that this unit should be/is a 1969 ram air IV and it is a XK code 3.90 ratio. If this is something rare I'd sure hate to mess it up by jerking the gears out of it ( No, I don't EVER throw away parts) any thoughts? Thanks much ! ! Steve.
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post #2 of 13 (permalink) Old 01-03-2011, 07:42 AM
 
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axle tube stamp is hard to see as it is just a hand stamping, two letters located on the passengers side tube around 12" from the pig either top or bottom, need top get some sandpaper and scuff it down to see it. Housing castings were often same year to year so it may be correct. is it 12 or 10 bolt? If 12 its definitely a keeper. that gear (3.90)will be great corner to corner but will be a pain if you plan on freeway driving for any length of time.
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post #3 of 13 (permalink) Old 01-03-2011, 07:43 AM
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That would be correct Alaska..... Fo a '69 the 2 letter stamped code will be on the backside of the driverside axle tube.. You should also find a date code cast by the pumpkin... The 9795084 casting code also came in a 3.55 and 4.33 gear...



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post #4 of 13 (permalink) Old 01-03-2011, 11:31 AM Thread Starter
 
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Thanks.I'll keep looking, and I really don't need 3.90's here....3.23 or 3.55 at the most.
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post #5 of 13 (permalink) Old 01-03-2011, 11:33 AM Thread Starter
 
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Thanks for the info. There's just gotta be number there somewhere. I need a 3.23. or 3.55 I'll post it later, but since it is just a 10 bolt I'm not going to get too weird about it. Thanks, Steve.
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post #6 of 13 (permalink) Old 01-03-2011, 05:59 PM
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Ten bolt will be the stock rear end if the car was a 400 engine car. A 3.23 or 3.36 gear would be ideal.....3.55's are no fun on the open road at all. If the rear end is indeed original, and a 3.55, you can fit it with 3.36 gears, if you can find 'em.
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post #7 of 13 (permalink) Old 01-03-2011, 10:19 PM Thread Starter
 
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good advice; I'll pay heed. The people that sold it to me said something about a rear end swap that was done....????...now solid info on that. Since I have plenty of time between now and break-up ( when the river ice breaks up in the interior of Alaska) and I can actually get it out, I'll pull the diff and R&R the suspension. Any thoughts there? I mean, it's a bit overwhelming. Everybody wants me to buy their stuff. Left to my own devices: New upper and lower control arms, boxed, rubber, not poly....new stock springs and isolators and set of good quality shocks. And while I'm in there, new break lines and parking brake cables. This car came from Ohio, and the shop that did the paint loaded up the underside with undercoating. man..what a mess.............And of course, the gears. I wish somebody here did dry ice blasting. You can find it in America, not here. Thanks!
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post #8 of 13 (permalink) Old 01-03-2011, 11:13 PM
 
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all depends on what you expect out of the car, stock suspensions is more than adequate for cruising and a little spirited driving, if you like a more aggressive feel upgrade to poly bushings, and stock front discs. not a wallet buster and unless your worried about shaving tenths in autocross you should be happy with the ride and handling when called upon. The 10 bolt should be fine unless you plan on making that 400 into a stroker and like GeeTee siad if you can get the 3.36 its a straight swap and there you should'nt have a problem re-couping some cash if your gear and pinion are in good shape.
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post #9 of 13 (permalink) Old 01-03-2011, 11:26 PM Thread Starter
 
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polygraphite bushings in new control arms are available. You like them? I'm more into average driving. I do not intend to start a 'fight' at the stop light. I wouldn't mind finishing it, though.... ;-) I'm new to this and I do appreciate the enthusiasm from other pontiac people. I don't have aproblem with going poly, someone once said that it's really hard on the car and I'd eventually tar up the suspension. Roads here are NOT nice. Stretches of gravel, with potholes and frost heaves, broken pavement and bad curves. After that, it just gets bad....I'm just sorta' kidding. Ok.I'll go poly. the car came with stock front disc brakes, so that's good. On another note, I found a build sheet on top of the tank. If you see a '71 bonneville 3-seat wagon limping around, let me know..............I've got HIS build sheet.....
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post #10 of 13 (permalink) Old 01-04-2011, 01:06 AM
 
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i am from Detroit, i know all the clowns that work at the plants, nothing surprises me. with the roads i would probably stick with stock bushings they will soften the ride a little and most of our cars are'nt daily drivers and are garage kept so they should hold up well, if she has a lot of pitch cornering a new set of springs and some gas shocks will go a long way to tighten the handling up too. post some pics when you get them

heres what i am working on:

1966 Tempest pictures by instg8ter - Photobucket
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, Lemans & GTO General Discussion

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