Why do GM full size SUVs still have a live axle?

"javiIn1080p" (javi1080p) 01/13/2016 at 11:53 • Filed to: None

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So this is a thought I’ve had for a while- why hasn’t GM replaced the live axle on the Tahoe, Yukon, Suburban, Escalade with IRS like the Expedition by now? The one benefit of the live axle is better capability offroad, but the new GM SUV have such a long wheel base and an air damn hanging off the front bumper that’s only ~4 inches off the ground that you can’t seriously offroad them anyways. Are they just being lazy and saving the investment to switch the platform to IRS? I don’t know how everyone feels, but considering a loaded up Escalade can hit almost $100k, I’d expect for them to have switched to IRS by now.

Demon-Xanth knows how to operate a street. > javiIn1080p 01/13/2016 at 11:56

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Simple, cheap, durable, used on all the trucks anyways.

HammerheadFistpunch > javiIn1080p 01/13/2016 at 11:58

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the GMT platform (yukon/tahoe/suburban) stands for General Motors Truck, and its directly shared with their pickup line. The reason they don’t change it is simple: why should they? They are selling better than the Ford and making a higher profit and aside from rear passenger space, there aren’t that many downsides to it.

Party-vi > javiIn1080p 01/13/2016 at 11:58

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I mean, there’s more than that one benefit, but considering the Escalade and the other Chevys sell damn well with a live rear axle why would they want to decrease profitability and re-engineer IRS into it?

Birddog > javiIn1080p 01/13/2016 at 12:01

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Money.

From a review on Cars.com.

“Jeff Luke, GM’s executive chief engineer for full-size and midsize trucks, said an independent rear suspension was considered for the full-size SUVs, but they decided to use a live rear axle like past models so they could spend program money elsewhere.”

Highlander-Datsuns are Forever > javiIn1080p 01/13/2016 at 12:07

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In my experience they work pretty darn good. I had an air ride suburban and that thing was the best ridding car/truck I have ever driven. With real 4wd and a sold rear axle it was very good on forest service roads, mud, ice and snow. It’s not an FJ cruiser off road by any means but I would take it places I wouldn’t take my Subaru Outback (mainly because it was a work truck and I didn’t have to pay for repairs).

RamblinRover Luxury-Yacht > javiIn1080p 01/13/2016 at 12:12

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The one benefit of the live axle is better capability offroad

Well, no. Modularity for different capacity platforms, extreme durability and strength, low cost, mechanical simplicity, capacity for future upgrade, parts-sharing with actual truck lines for all those reasons, minimal ride quality and grip difference with a high weight platform, driveline packaging, aftermarket support, and any number of other things. You can make an argument for IRS on many things, but only minimally on anything that’s actually a truck.

Smallbear wants a modern Syclone, local Maple Leafs spammer > javiIn1080p 01/13/2016 at 12:18

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Cheap, durable, and they’ve made work damn well, both there and on the pickups.

Why change? It still wipes the floor with FoMoCo in sales.

MontegoMan562 is a Capri RS Owner > javiIn1080p 01/13/2016 at 12:21

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There’s pretty much ZERO benefit of changing to an IRS on the full size trucks.

Why would you want it? What benefit do think it will provide to these big SUV’s?

javiIn1080p > MontegoMan562 is a Capri RS Owner 01/13/2016 at 12:28

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because they’ll ride better. The porsche cayenne is miles ahead of a suburban with air suspension.

Textured Soy Protein > javiIn1080p 01/13/2016 at 12:36

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Because it would cost money to re-engineer the platform to an independent rear end, and people buy GM full-size SUVs like crazy without GM spending that money.

DoYouEvenShift > javiIn1080p 01/13/2016 at 12:39

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A Suburban and a Cayenne are totally different vehicles with different capabilities.

An Escalade rides better than a Navigator and a Suburban rides better than an Expedition. Especially a Suburban with MRC.

MontegoMan562 is a Capri RS Owner > javiIn1080p 01/13/2016 at 12:41

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They did air ride in these big GM trucks all the way back in the early 2000's. Have you ever ridden in these? They’re wonderful.

Also, not only is the rear suspension virtually indestructible with a live axle it’s also cheap to fix if something DID go wrong.

I’m also a lot more comfortable with the idea of towing with the Suburban’s truck gear than I would be in the Cayenne.

tromoly > javiIn1080p 01/13/2016 at 12:41

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Tow capacity, for one. Have you ever seen a Big Rig with IRS? Extreme example, but it’s true.

javiIn1080p > tromoly 01/13/2016 at 12:44

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It doesn’t seem to affect the Expedition. It can tow as much as a Tahoe

shop-teacher > MontegoMan562 is a Capri RS Owner 01/13/2016 at 12:53

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There would be one big benefit actually. An IRS would let them drop the rear floor (you don’t need room for the rear diff to move up and down, so that space can be moved to the interior). That would give more interior volume and more room for the third row.

I think they don’t do it, because they don’t need to. They already dominate the full size full frame SUV segment by a huge margin.

shop-teacher > javiIn1080p 01/13/2016 at 12:56

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The only real benefit to IRS for it would be increased interior volume and more room in the third row seating. They already dominate that segment in sales by a huuuuge margin, so why spend the money on an IRS? There’s no real handling benefit for such a huge vehicle.

tromoly > javiIn1080p 01/13/2016 at 13:48

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Indeed, but then you’re getting into limitatons with the frame, which wasn’t in the scope of the question.

Berang > javiIn1080p 01/13/2016 at 14:15

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The sort of people who buy these things know so little about what handling is, that they would never be able to tell the difference even if the live axel was replaced with something substantially better. GM therefore doesn’t have to spend money doing so.