Global West Rear Suspension Upgrades
 

I'll be swapping in a new Moser 12 bolt soon and it got me thinking about the rear control arms and bushings since I'll have it apart. I've never been in love with the polyurethane bushings back there, especially over bumps. It rides like a truck. For a mostly street driven car, how much of a handling improvement would I see with a Global West spherical setup? Is it overkill? Should I just go back to good old rubber bushings?

It sounds like you're doing something similar as I did to my '67 a few years ago. I also went to a Moser 12-bolt rear and switched over the rear arms to GW. Sure is nice to dial in your pinion angle easily with the adjustable upper arms. I elected to go with the del-alum bushings, which are actually more like a bearing. I will say, tho, that the rear lower arms are quite heavy, but I suppose they need to be for strength and compliance. I recommend them

ANYTHING you do back there is going to be an improvement over poly bushings, tho. They have a terrible bind-up problem, and I actually broke my right rear control arm due to poly bushings back in the 90's, when they were more popular...I'll never run poly. bushings again, except maybe for front stab bar links.

What's the advantage of Del-alum over polyurethane? Less squeaking and binding? I suspect the rear suspension in my car is binding over bumps because it feels very rigid over bumps. I could probably make it better by regreasing the bushings, but since I'll have it apart...

I'm also looking at UMI's kit which looks comparable to Global West's. However, it sounds like Moser rear ends have thicker mounts for the upper bushings since Global West offers a specific bushing for them. Not sure if UMI does the same.

https://www.umiperformance.com/home/...uspension-kit/

I also have GW rear control arms with the del-a-lum bushings and rubber in the rear housing uppers. No squeaks, no rattles and NO wheel hop. Highly recommend them.

In the rear…no advantage, to being a detriment, if the knock on poly is to be believed. Poly will at least give a little…delalum will give none.

The range of motion of the rear arms, at the axle and frame, call for something that “gives”. Rubber will…poly a little, the spherical types of bushings a lot. I have the hotchkiss versions, axle captured between two really high durometer plastic halves.

I’m in the minority, I’m a fan of poly, but I also know where it’s best utilized. At least I think I do…

The Global West pieces use a mix of spherical joints and del-a-lum or rubber bushings.

In a converging four link like that of the OP's 1986 GTO, the rear end must be able to articulate. Poly should never be used in the upper mounts because it can start to induce bind. Rubber is soft enough that it allows the axle to move in the directions that it needs to. For street applications where NVH is a concern, you always use Rubber bushings in the upper mounts (frame side and differential side) and at minimum on the frame side of the lower mounts. Poly can go in the differential side of the lower control arm.

Since this is a street car, with the Global West pieces I would run the following:
Upper Control Arms - TBC-82. Spherical frame side mount with factory Rubber bushing in the differential mount
Lower Control Arms - TBC-4. Spherical bearings on the frame side with del-a-lum bushings on the differential side

If you're not concerned about a little extra noise in the back, upgrading to the rear-end bearing kit SP-47M (for Moser) which changes the differential bushings to a spherical bearing, that will give you the ultimate in centering and articulation for the factory rear end.

It's important to note, these changes don't inherently give you better handling than what the car is capable with the factory setup and rubber bushings. What it does is allows the rear end to articulate properly and thereby gives you more tractability and linear progression towards the limits of adhesion. With rubber bushings and especially with Poly bushings, wheel rate is being added as the bushings take a crush and begin to bind. You're adding traction here until you reach critical bind, then the rear-end unloads and induces the snap oversteer that is characteristic of the converging four link design.

If you're doing the rear end, you may also consider going to coil-over shock, a sway bar and additional frame supports. I'd give Global West a call and talk to them about your needs based on how you're actually going to be driving the vehicle.

Appreciate the input so far.

Are the spherical bearings that Global West uses the same or similar as the "Roto Joint" that UMI uses? Just wondering if it's a brand name thing.

After doing some homework, I've been leaning towards what Jason recommended above. Either the Global West or UMI with the spherical joints on the frame side and poly or Del-a-Lum on the diff side. I believe the diff housing comes with rubber bushings already installed.

Since the 12 bolt is a direct replacement, I don't see the need to spend the extra $ on adjustable uppers since the pinion angle should be good. I also prefer boxed control arms to tubular purely for appearance, so I'm leaning towards UMI pieces.

I have a sway bar from a '70 GTO in the rear I'm going to retain along with the Bilstein shocks.

Lowers: UMI 4041
https://www.umiperformance.com/home/...rms-poly-roto/

Uppers: UMI 4036
https://www.umiperformance.com/home/...s-roto-joints/

The Global West joint appears to be more akin to a roto roint. It's not a spherical rod end, but a high offset spherical bushing. It shouldn't rattle like a rod end, but it's not going to be as quiet as a rubber busing. This is why the spherical joints are on the frame side only. The rubber bushings in the differential will kill most of the NVH.

My opinion, but there's no place in suspension pieces for Poly. If you're thinking you need something with less deflection than rubber for a piece that moves in a single plane, you want the delrin bushing.

Think about what they make super balls out of then ask yourself why you'd put that material in your suspension. The answer that you'll inveriably come it is that it came down to cost. Polyurethane is far and away cheaper then quality rubber or delrin.

If you are changing ride height at all on these, you really should have the adjustable uppers. If the car is staying at factory ride height, then using non-adjustables would be fine.

In fact I would go as far as to say that if you don't believe you'll need an adjustable upper arm, I wouldn't even worry about purchasing them unless your stock pieces are in need of replacement. Instead, use the factory uppers with rubber bushings on both the differential and frame side, then go with an aftermarket lower with the spherical frame side and delrin differential side.

If you're set on doing both the uppers and lowers, get the adjustables, being able to dial in your pinion angle will benefit traction, NVH, handling etc.

I hadn't considered the ride height change. My car has 1" drop springs so maybe there's an opportunity to better dial in the angle. Admittedly, I'm getting caught up trying to pinch pennies after shelling out for the rear end, but at this point what's another $100 to get it setup correctly?

If your ride height is altered at all, get the adjustable uppers. I battled this with my wife's old Chevelle. It had been lowered fairly significantly in the back and the previous builder sectioned and welded the factory upper control arms where they thought the pinion angle would be correct. It wasn't.

You're putting a big boy rear end in this thing to use that big boy power you've got from what appears to be a pretty stout engine up front. You're going to want to use this stuff. If you don't buy the adjustable piece now, you'll probably find that you need them later, or at least want them so you can make the car perform better. Spend the 100 or so extra now, or pay double by buying two sets over time. That's kind of the situation that is being set up here.

Doug from Global West did a 3 part series of vids regarding bushings, bind, etc, it's a good watch:

https://www.youtube.com/watch?v=u0IvDkMV_q8

https://www.youtube.com/watch?v=hPO-G5wLD54

https://www.youtube.com/watch?v=aDR5y4hsdik

Not sure I got them in the correct order, but I'm multi-tasking at the moment...


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I watched those videos the other day which is what got me thinking about spherical joints.

I just ordered the TBC-82 and TBC-4 control arms from Global West. Gonna have to plan for a really nice Mother's Day for my wife when she sees all the boxes arriving.

That's what I run, same setup, with the spherical bushings on the housing ears. Also run the TS-82 braces. Absolutely the best available IMO.

When it becomes totally free movement back there, shock tuning finishes it off entirely. You can autocross, road course, drag race, etc simply by changing shock settings. I have QA1s 2x adjustables but Vikings are great too.

If you can swing it, AFX spindles and either Speedtech uppers & lowers makes for the best setup just shy of a full chassis.

I did the ABC solid body bushings too.


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I have a set of stock 4-speed frame braces on there now. Maybe at some point I'll upgrade to the Global West version. I was looking at the spherical bushings for the housing ears, but wasn't sure they made much sense if I have the del-a-lum bushings on the diff side on the bottom.

Now that I've got everything installed and dialed in, I wanted to circle back and say you were absolutely right about the upper control arms. I set the control arms to factory length for the initial install, and that had the pinion pointing down 3 degrees. I'm sure this was due to the way they moved the mounts up on the housing. It took a good bit of adjustment to get the drivetrain in alignment.

I had the car out today for a bit for the first time since the rear end swap, The bucking bronco over bumps is completely gone. Overall, it feels more planted so I'm happy with the outcome.