Raising rear end height - Pontiac GTO Forum
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post #1 of 24 (permalink) Old 05-05-2018, 12:06 PM Thread Starter
 
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Raising rear end height

I have always felt the rear of my 65 GTO was too low, as long ago as the mid seventies ( so I do think not the issue is weak coil springs, but fatigue could be exacerbating the situation). While doing my frame-off, I had a 4x4 post in between the body and the chassis. I really liked the look of the rear being raised. I have seen some inexpensive blocks for the coil, which strike me as a really bad idea. Adjustable coil-overs look promising, but I don't know if I can get 3-4 inches of height out of them; also not sure they are worth the investment. I thought about fabricating my own rectangular metal blocks and getting longer body bolts where needed before I reassemble the body and chassis. I thought I would pulse forum members for comments. Please fire away.

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post #2 of 24 (permalink) Old 05-05-2018, 04:15 PM
 
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There are a number of ways to do this. Air shocks are NOT the way. The top brackets to which the air shocks bolt to are not very strong and essentially you are lifting the car using these brackets - they will fatigue and break over time.

Taller springs from a station wagon will lift the rear up, but not 3-4 inches. You'll get a couple more out of them. Do a search using the Search feature on this site and you will get a number of ideas and spring choices.

The next option to get the car up 3-4 inches is to put a pedestal under the coil springs to which your coil spring will ride on and the pedestal seats on the rear axle where your spring would normally seat. You want something like this: https://www.ebay.com/itm/3-Inch-Pont...4AAOSw4-hZr6Aq I loaded up a pic of my '68 Lemans with the 3" lift pedestal. You will want to drill a hole in the center of these so you can run a threaded rod down them to attach them more securely to the axle housing mount. I also plan on using some form of attachment to keep the base of the coil spring secured to the top of the pedestal.

But, don't get all googlie eyed just yet. Adding the lift will change the geometry of the rear suspension. Those upper control arms are going to be at a severe angle and almost useless - if they don't simply hit the rear crossmember near the attachment. Wheel hop can already be a problem with the stock ride, but add the lift, you might have more problems on your hand. First, you will have to add a little more extension to your shocks so they work correctly and are not "stretched out" so as to make them worthless. Next, to correct the upper control arm angle, you will need to raise them up at the rear end side. "No Hop" bars can do this and they are sold aftermarket under several names & companies. I fabricated my own to fit the 9" Ford I'm using as no one makes a bolt-on for such an application. Don't forget to use a longer rubber brake hose so the stock one isn't so stretched out all the time.

Then jacking it up will most likely affect your pinion angle and to counter this you may want to consider adjustable upper/lower control arms to get things back in line again.

Now with that all done, you have changed the center of gravity and the way the ass-end is going to shift around - so add a sway bar set-up to counter that situation.

BUT, I'm not done yet. All that weight is now going to be somewhat shifted forward to the front of the car and the stock springs may not have sufficient spring rates and you could find a more "bouncy" front end as well as steering differences - ie under steer or over steer. I went with a rather stiff 1970 Chevelle 454 spring as I also want my car to sit high in the nose to go along with the raised height of the rear. Front brakes may be affected as the weight shifts forward when you hit the brakes - better have disc's and an adjustable proportion valve to get this set-up correctly. Wide rims/big tires will round it all out on my build for a little better traction/handling overall.

Yep, the jacked-up look is from the '70's era and looks cool to me because that's what I grew up with and am modelling my car after - except I am doing it right and doing it safer.
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post #3 of 24 (permalink) Old 05-05-2018, 09:08 PM
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Originally Posted by JNYBOY View Post
I went with air shocks on the rear...Don't "Goldberg" your baby !
Bad move human, the upper shock mounts are not designed to carry the body and will eventually develop stress cracks.

Here is what I used.

https://www.summitracing.com/int/par...tiac/model/gto

Here is how much it lifts from stock which is a little lower in the rear than the front from the factory.
I just wanted a slight rake, the 1 1/2 was too much and I sent them back for the 1".
I also used Lexel to adhere them to the perches.
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post #4 of 24 (permalink) Old 05-06-2018, 01:44 AM
 
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jnyboy please resend link it does not work
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post #5 of 24 (permalink) Old 05-06-2018, 11:55 AM
 
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1964-1966 GM A-body rearends did not use the round locator type coil spring mounts that the '67 and later style A-body housings did. Original '64-66 housings used a stamped steel bolt on "Ear" shaped retainer that clamped the bottom loop of the coil spring to the spring perch of the early A-body rear. Attempting to use one of the aftermarket round cast alum spring spacers, it's not going to locate on an original '64-66 A-body rear without making a steel plate to fit on top of the '64-66 spring perch, then a hole would would need to be drilled in the cast alum spacer as well as the steel plate, and then the could be secured to the rearend perch. The taller the cast rear coil spacer, the more pressure that's going to be on the protruding top of the cast spacer, have ran across such damaged alum spacers numerous times.

Simple reality, original coil springs settled over the years, & original rear springs are not made to near the lbs/square inch as the fronts. with numerous heavy loads hauled in the trunk the rear does not take long to settle. Have found its very common to run across even relatively low mile A-body's where the rear has settled down considerably lower than stock ride height. The 4,000 mile original Pontiac plant build '72 Lux LeMans that I've kept around for near 2 decades as an example car to help with the cutting edge restoration of one of my 71's, as well as the restorations of 2 of my '72 Pontiac A-bodys is a perfect example. That particular Lux LeMans sets over an 1" lower than stock rice height with its trunk empty & it has been off the road since the summer of '72 when it was lightly rolled.

The easiest solution to increasing rear ride height, as well as the way with the least ill consequences to raise a '64-66 A-body with early style rear is to order a pair of taller similar rate rear springs. Moog used to offer taller stiffer rear springs to compensate for the extra rear vehicle weight of convertibles and station wagons. Have pulled numerous aftermarket pairs of these taller rear springs over the years while in the course of pulling 8.5 A-body & 12 bolt Chebbie core rearends. Have personally been under thousands of 60's and early 70's GM A-bodys and have come across all kinds of "Rig" jobs. Many such deals just make you shake your head in disbelief! Use to be, an owner was able to go down and order taller Moog rear aprings at the local autoparts store, but Moog has sinced thinned its older spring offerings. Coil Spring Specialties in KS is who I've ordered coil springs from for many years. CSS has all the factory spring charts, understands coils spring design, and can supply a taller rear coil spring which should be able to raise the rear of an early A-body by 3- 3 1/2 inches. Much more than that & the car will be getting to a point where the braking bias is going to be effected,, much more braking being done by the front brakes and very little by the rear.
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post #6 of 24 (permalink) Old 05-06-2018, 12:15 PM
 
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Bad move human, the upper shock mounts are not designed to carry the body and will eventually develop stress cracks.

Here is what I used.

https://www.summitracing.com/int/par...tiac/model/gto

Here is how much it lifts from stock which is a little lower in the rear than the front from the factory.
I just wanted a slight rake, the 1 1/2 was too much and I sent them back for the 1".
I also used Lexel to adhere them to the perches.
Bad move "Human" ?? And you're listed as a Super Moderator ?...Figured a "Super Freakin' Moderator" would be above name calling, and generalizing the input and comments (right or wrong) from members on the site. Poor judgement IMHO !

Last edited by JNYBOY; 05-06-2018 at 12:16 PM. Reason: Another Thought !
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post #7 of 24 (permalink) Old 05-06-2018, 12:59 PM
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Bad move "Human" ?? And you're listed as a Super Moderator ?...Figured a "Super Freakin' Moderator" would be above name calling, and generalizing the input and comments (right or wrong) from members on the site. Poor judgement IMHO !
I don't see where I called you a name, just pointed out your advice will damage people's vehicles.
Feel free to contact the admins and lodge a complaint.
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post #8 of 24 (permalink) Old 05-06-2018, 03:32 PM
 
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jnyboy please resend link it does not work
K,..I won't "resend" my post, but I will "rescind" it, as the gods have spoken and I see dark clouds on the horizon ! J
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post #9 of 24 (permalink) Old 05-06-2018, 06:30 PM
 
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Quote:
Originally Posted by JNYBOY View Post
Bad move "Human" ?? And you're listed as a Super Moderator ?...Figured a "Super Freakin' Moderator" would be above name calling, and generalizing the input and comments (right or wrong) from members on the site. Poor judgement IMHO !

Really? Name calling? I think Goat Roper was being a little jocular based on the photo that appears with your forum name. You obviously are very thinned skinned and must be new to the GTO forum as name calling is not Goat Ropers style. I on the other hand would - and think you an ass. Perhaps a old Yugo might be more to your liking rather than something manly like a GTO? Yep, and you can report me too to Human Resources as well.
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post #10 of 24 (permalink) Old 05-06-2018, 08:40 PM
 
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Really? Name calling? I think Goat Roper was being a little jocular based on the photo that appears with your forum name. You obviously are very thinned skinned and must be new to the GTO forum as name calling is not Goat Ropers style. I on the other hand would - and think you an ass. Perhaps a old Yugo might be more to your liking rather than something manly like a GTO? Yep, and you can report me too to Human Resources as well.
PJ,..Thanks for your input... "Thin skinned" ?...I think not, although that "Human" comment did get my attention, as I don't like being talked down to... And I wasn't aware of your fact that owning a GTO makes one manly ? Wow !!...Perhaps I should buy several more huh ??..How many do you think ?.. Times have really changed... Do a little research on the Avatar, it might also give you an idea of my manhood ! ....Didn't mean to create such a kerfuffle on the forum, but it is what it is !
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