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Rear Spring swap

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vping

vping

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I touched on this a few months ago but what ill effects will I have if I swap the entire rear setup from a 74 GT and drop it in a 74 Roadster?

Here's why. I just got the Roadster roadworthy and the rear is not as tight as I think it can be. A urethane bushing kit has been aquired and it ready to go in but I'd like to pull the whole rear, clean it up and then reinstall. My problem is I like to clean things up more so than the average bear and like to sandblast prime and paint everything. This will take some time and leaves the car sitting on jack stands not able to be moved and it is imperitive that I keep the car mobile with all the other projects that are always going on. From the parts car I have a ubolt setup that I brought to work today to clean up. Then it dawned on me that I have the entire rear setup. Why not make that perfect and then lift it in will all my new bushings?

So back to the initial question will I have any ill effects of putting a 74 GT rear in a 74 Roadster?
 
I think with the GT springs, your roadster will sit too high in the rear (& possibly ride harder)....change out everything except the springs & you'll see no adverse effects.
 
GT springs are stiffer. You don't want them in a roadster, in my opinion. You can put the car on dollies while it's apart, or if it really needs to roll around then bolt up the GT rear end (it's only 4 bolts) and swap it out when the project is done, completing brakes, drive shaft, etc at that time.
 
Maybe a mute point anyway. Ever think of a great idea then you act on it and go DUH!. The GT setup I have is a WW and the roadster is not. I'd almost have to put the GT rear in it in as a temp in order to move it around or put it on dollies as suggested.

Is there an effective way of removing a leaf thereby making it "less stiff" for the Roadster?

Are the brake backing plates, shoes and cyls different on a WW car? Maybe I can at least take these and start to refinish them. (the backing plates anyway)
 
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Is there an effective way of removing a leaf thereby making it "less stiff" for the Roadster?[/QUOTE]
Sure, just disassemble the spring & remove 2 springs - not one....easy thing to do.
 
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Are the brake backing plates, shoes and cyls different on a WW car?[/QUOTE]Not sure about the backing plates although I believe they are identical. The mounting holes for axle ends are the only thing I can think of that might need to be changed. The plates and cylinders are different between GT and roadster though.

You can remove a leaf, but there's no guarantee that the resulting spring would be an equal rating to roadster springs. The general feeling is that softer is better than harder.
 
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Not sure about the backing plates although I believe they are identical. The mounting holes are the only thing I can think of that might need to be changed. Wheel cylinders are the same.[/QUOTE]
Back plates & wheel cyinders on the GT are different than those on a roadster - but, who cares if you're swapping the whole rear end?
 
Do you get better rear braking by using GT cyls?
 
You will get more power to the rear brakes, but that doesn't mean better braking. In fact it will upset the balance in favor of the rears which can result in locking the rears well before locking the fronts. If an imbalance happens, it can also result in a spin should you hit the brakes in a turn or emergency maneuver. GTs are heavier cars and it's all in the rear, so they can handle more power to the rear brakes without locking up. Of course everyone has a bit different of a suspension, wheel, tire and brake setup but I'm talking about a car in stock condition.
 
Brings up another question. If you are running fatter than stock tires would it benefit to have GT clys?
 
In my opinion, only if you've uprated the fronts as well. Of course this opinion has no basis in real world testing and every car is different. You want to keep a proper balance front to rear for any given setup. Once you change from stock, all bets are off! If you're running wide stickies, you may find more powerful brakes of use. However the stock brakes can lock up all four tires even with wider than stock rubber so unless you're looking for less pedal effort or running really sticky tires, you probably won't see a benefit for the money spent. In addition, you can install a brake bias valve so you can fine tune the brakes no matter what type of tires and brakes you have.

I can tell you really want to be able to use the GT stuff to keep the car rolling. The basic fact is that it will work fine. You will have a little more power to the rear brakes and the rear suspension may sit higher than stock and ride harder. Remove one leaf (GT has 7, roadster has 6) and it will probably replicate the roadster spring rating. The biggest issue between the two rear ends will be the condition of the diff gears. Why not inspect the two and use whichever rear end has the better gears? Just install the GT stuff since it will only be temporary and reinstall the roadster parts when they are done.
 
I think I'll give the GT springs and brakes a shot. I know nothing different so I'll have nothing to compare if it is a stiffer ride. Can you use Roadster cyl rebuild kits on GT cyls? I ordered a set but am not sure if they were for my Roadster or GT. Chances are it was for the GT which means I am in luck. Now I just need to sort out the piping back there and the parking brake cable.
 
Roadster & GT cylinders are different bores - different kits for GT's from 1968 onwards.
 
That post made me think of another slight dilema. The rebuild kits I purchased for my 67 GT may not work anywhere. My GT has a Banjo rearend. PO not me. So I have rebuild kits I assume I purchased for the 67 and rear brake componenents I may use are a 74 GT. Maybe I'll take an extra day, pull the rear, do all the brakes, detail and paint it and reinstall but might use the GT springs.

OHHH PO's! Althought if I put the GT springs in it would I be called a DPO? /bcforum/images/%%GRAEMLIN_URL%%/devilgrin.gif
 
Yes, you would. /bcforum/images/%%GRAEMLIN_URL%%/grin.gif
Among other things. /bcforum/images/%%GRAEMLIN_URL%%/devilgrin.gif
Jeff
 
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]The rebuild kits I purchased for my 67 GT may not work anywhere. My GT has a Banjo rearend. PO not me.[/QUOTE]
Your rebuild kits should work on that banjo rear end so long as you use '67 or earlier cylinders,

&, yep, you're bordering on DPO status...hehehehe
 
So, that would be DCO - Dreaded Current Owner - no?
 
Another thing to think of with switching is that forever on, whoever owns the car will have to ponder what parts to buy and then go through the hassle of figuring out what the heck happened and reordering parts everytime they mess with the rear end. Someone did this switcheroo on my GT(the axle and brakes are from a roadster) and it has caused me no end of consternation in figuring out why the cylinders I ordered wouldn't fit (I ended up sending my parts back twice before figuring out that they were sending the right parts, but my backplates were the wrong ones). That combined with the possibility of throwing off the braking balance (there is an engineering reason the manufacturer went with different cylinders for roadster vs GT) makes me say..."Keep it stock!"
 
Well I was contacted last night and someone wants my rear. (not because I might become a DPO) My WW rear!. He has a non WW rear he's willing to swap me for and may even take it apart and check it out making sure it's tip top. So I'll have what I need to keep all the parts matching the car.

"Keeping it stock!"
 
vping said:
Well I was contacted last night and someone wants my rear.
Click to expand...
you know......... It's a good thing we're talking about car parts! Otherwise we might have to report you to the authorities! /bcforum/images/%%GRAEMLIN_URL%%/jester.gif
 
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