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#1
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69 GP Rear Diff. question
What would have been the most common Rear Diff. for a 69 GP.Model J ? I have the PHS information on my car ,but it doesn't state what rear it has . I thought they all came with a limited slip . If someone can shed some light on this ,I'd really appreciate it .
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#2
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Owned a '69 GP Model J a while back, it was a 400 auto trans car with A/C. I'm guessing most would have been oedered by the dealer or individuals equipped that way since it was a luxury car.
It had a 3.23 open rear, I opened up the diff and replaced the gear lube so I know it definitely didn't have a Safe-T-Trac posi unit.
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1964 Tempest Coupe LS3/4L70E/3.42 1964 Le Mans Convertible 421 HO/TH350/2.56 2002 WS6 Convertible LS1/4L60E/3.23 |
#3
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69 GP rear end
you can find out the rear end on your car one of several ways.
1. get the PHS on the car and see what it came with 2. get the car up in the air and look on the axle housing on the left side. You may need to take a wire brush. You are looking for a two letter code. first letter is either "U" or "V" V = posi-trac, U = open. The second letter tells you the gear. Look in the service manual. Example UF = 3.08 open Also the inside of the brake housing on the drivers side rear will have the code as well. 3. Get the car up and turn the wheels to count the revolutions on the shaft. Yes, certain rear ends were std with certain engine packages. 428's usually got a higher gear. A 428 HO car with A/C would have likely had a 3.42 or 3.23 rear. I don't think a posi was std on anything. You had to order that.
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'69 Bonneville convertible Warwick blue/ parchment interior 53 option accessories 2 more to go :-) |
#4
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69GP Rear End
Is it on the backing plate ? I read somewhere that it is on the Drum . I checked that and the #'s don't make any sense . Like something is missing ! They have probably been changed out at some point . Thanks for the info !
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#5
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I've parted out a lot of GPs over the years, mostly 428 cars.
Most of the 428 cars I dismantled had 3.23 rear ends. I live in NC, so most were open rear ends. The limited slip rear ends I've encountered were mostly out of manual transmission cars and 428HO cars. I found a 69 GP 400 car with a 2.92 limited slip rear end. I also found a 69 428HO 4-spd car with a 3.55 limited slip. I've seen a lot of 3.08 rear ends in the 70-72 400 cars. Hope this helps. Mike |
#6
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All 69 GTO/GP cars that were optioned with A/C the highest gear Pontiac put in them was 3.23 . This was irregardless of engine 400/428 in the GP. The standard GTO 400 and RA III cars were same too, but on the RAIV GTO they got 3.90 gears were standard .
If the car was not A/C and non optioned for rear gear than standard were 3.55 ratio open. And could be optioned with 3.23 open or 2.92 open etc. The Safe-T-Trac could be added to all ratios from 2.92, 3.23,3.55 rear ends. But even if the Axle performance option( 3.90 gear) was ordered then it still shows the Safe-T-Trac option on PHS. Mike is correct the 3.08 is very common 70-72. I would as blu bomber says look on axle for some codes of try rolling rear wheels to determine. Ben : Do you have your PHS ? Dave |
#7
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Quote:
(some years had it, but would have to look it up for which ones)
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John Wallace - johnta1 Pontiac Power RULES !!! www.wallaceracing.com Winner of Top Class at Pontiac Nationals, 2004 Cordova Winner of Quick 16 At Ames 2004 Pontiac Tripower Nats KRE's MR-1 - 1st 5 second Pontiac block ever! "Every man has a right to his own opinion, but no man has a right to be wrong in his facts." "People demand freedom of speech to make up for the freedom of thought which they avoid." – Socrates |
#8
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When all else fails you could drop the cover and count the teeth and change lube while at it.
Wipe spot off on R&P and mark a tooth with something for reference.. Done that many a time...
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ECM member. 2008 Outlaw Pontiac Drag Series Champion MANDRA Do it now fool! Life is short. 69 Grand Prix/3163lbs / IAII 535 w/ Tiger heads by Gaydosh....9.35@ 144 so far.. through mufflers. 1.26 60'. Going back to track with pump gas engine.... My 60 Ventura retired to street/strip duty.. |
#9
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Pontiayak,
For some reason, I don't think I ever pulled a 3.08 out of a 69 Grand Prix. I would estimate about 75% of the cars I parted were 428 cars with a/c, and just about all of those came with 3.23s, both open and limited slip. The few 1969 400 powered cars I picked up had 2.92s. In 1970, the 3.08s were more common than the 3.23s. I think part of the reason is the 455s had 12-bolts, so I didn't part that many 400 cars. Mike |
#10
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If you go to the trouble of removing the cover the number of teeth for both of the gears is stamped on the edge of the ring gear. Just divide the smaller into the larger to get ratio.
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#11
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69 400 Auto with AC, 99% chance it's a 2.93.
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My Break Away Squad 1969 Fbird (Base, 350 & Sprint Cvt’s - 400HO & TA Hardtops) 1969 LeMans (2dr & 4dr Hardtop and a Cvt) 1969 LeMans Safari 2 seat Wagon 1969 GTO (2 Cvt, 2 Hardtops & Judge Hardtop) 1969 Catalina (3 Cvt’s & a 2dr hardtop) 1969 Ventura 2 Seat Wagon 1969 Executive 4dr Sedan 1969 Bonnie Cvt 1969 Bonnie 3 Seat Wagon (2 of them) 1969 Bonnie Brougham (4dr Hardtop & Cvt) 1969 Grand Prix SJ (2 of them) 1969 2+2 2dr Hardtop (Canadian model) |
#12
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69 Rear Diff. question
Hey Dave , I do have the PHS Doc. ,but it doesn't have any rear end info on it . I think the inspection cover is going to have to come off to get this solved . Thanks for the info !
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#13
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69 GP rear Diff. question
My 70 4 speed G.P. has 3:31 ratio with a 12 bolt. Have owned several of these cars but this is the 1st one with this rear diff. All others have been 10 bolt with 3:23. Just my 2 cents.
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#14
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If original pig/rear still in it, I would bet 3.55 if no air . And 3.23 if has cold blowing a/c .
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