1998 GMC 3500 HD Overhaul - Crew Cab Commercial Chassis GMT-455

[motas02]

Restored original intake. I did have some love for the K&N. Its kina cool to look at, but I feel its mostly a lability. Cab noise has been drastically reduced since install. I would recommend to others.

 

[Supercharged111]

And no loss in power.

 

[someotherguy]

Unfortunately two of the Alcoas got mangled by a Timmy at the tire shop so.... they are used on the inners now
Rear lighting is still in progress. To my knowledge there should be no issues with the LED bar.

Curious - you've got all 6 aluminum wheels mounted? All the Dana 80's I've seen wouldn't allow for this due to not enough width on the hub flange to mount 2 aluminum wheels, as it necks down. These are hub piloted wheels (I'm sure you know that, just mentioning for other readers) and there's just enough width of the pilot area for two steels, or one steel/one aluminum.

Alcoa 19.5 mounted as an inner on a Dana 80 - note how little hub flange is left showing in the pilot area:

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And with the outer Alcoa mounted, no contact with hub flange, it's all riding on the studs which is not advised.

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You could theoretically cheat by using the clamping ring from the steel wheels and the conical seat lug nuts that go with it, but those IMO are really just meant for converting conical seat lugs (stud pilot) to use on a hub pilot wheel that has flat lug holes, like the 19.5 wheels have, but with no hub contact on the outer wheel, I don't believe this is wise at all.

Not to belabor the point but this last pic is with a steel inner mounted, you can see the witness marks of the outer steel wheel where it contacts the hub flange. Not much room left, but this is the design, and it's the whole reason I'm curious about your 6 aluminum wheel setup.

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Richard

 

[someotherguy]

I do apologize for my ignorance, but I am extremely fascinated… what’s the difference from this to a regular c3500 crew cab dually? GMT 455…? I’m here to learn! Haha

It's a GMT400 cab on what is essentially an P30 HD / RV chassis. A "parts bin build" from GM to create a "light" heavy duty truck having lower ingress/egress heights than actual medium duty trucks. Chassis cab frame configuration (34" spacing, parallel, flat frame rails from rear of cab), straight axle front end, 2WD only (4WD conversions offered by 3? different aftermarket companies), 19.5" wheels (5 lug front, 10 lug rear, 5/8" studs), Dana 80 rear axle (first year or so also saw some Rockwell axles), 4 wheel disc brakes, parking brake mounted on transmission tailshaft, 15K GVWR. Uses all GMT400 cab (mostly just regular cabs, a few crew cabs, never extended cabs though some people built a few custom), front clip, interior parts, other than the "grab handle" exterior door handles, and the taller bumper/grille filler panel required by the taller frame/core support, as well as the fender flares to match (not the same parts as light truck 4WD flares but same appearance.) That's pretty much it, in a nutshell. Oh and the engines were pretty much strictly 7.4 and 6.5td though there are the elusive first couple years with 5.7's, very few were sold this way. It took someone showing me a VIN tag from one to convince me it was factory equipped. IMO the few you do see with 5.7's replaced a blown-up 6.5td. The final two years, 2001-2002, were 8.1 or 6.5td. Transmissions were 4L80E and NV4500.

Richard

 

[motas02]

Everything you have stated is correct.

The forged Alcoa rims are currently the inners, and the outers are new aftermarket. During my install I was able to get good hub contact with the outer wheel center on the hub. The contact area is limited, but it's there and centered. I also believe that my Alcoas could be thinner than the wheels in your picture, which would give me more contact. There is a significant difference in the thickness of the forged Alcoa and the aftermarket wheels at the hub. 3k after install and I have not experienced any issues with balance or vibration. Ill try to grab some pics the next time I pull them off.

Curious - you've got all 6 aluminum wheels mounted? All the Dana 80's I've seen wouldn't allow for this due to not enough width on the hub flange to mount 2 aluminum wheels, as it necks down. These are hub piloted wheels (I'm sure you know that, just mentioning for other readers) and there's just enough width of the pilot area for two steels, or one steel/one aluminum.

Alcoa 19.5 mounted as an inner on a Dana 80 - note how little hub flange is left showing in the pilot area:


And with the outer Alcoa mounted, no contact with hub flange, it's all riding on the studs which is not advised.


You could theoretically cheat by using the clamping ring from the steel wheels and the conical seat lug nuts that go with it, but those IMO are really just meant for converting conical seat lugs (stud pilot) to use on a hub pilot wheel that has flat lug holes, like the 19.5 wheels have, but with no hub contact on the outer wheel, I don't believe this is wise at all.

Not to belabor the point but this last pic is with a steel inner mounted, you can see the witness marks of the outer steel wheel where it contacts the hub flange. Not much room left, but this is the design, and it's the whole reason I'm curious about your 6 aluminum wheel setup.


Richard

 

[someotherguy]

If your Alcoas are indeed thinner than the ones I had, someone may have milled the mounting faces of them. I don't think there are more than 2 part #'s for that style of Alcoa wheel in that size and bolt pattern, and the 2 numbers are just polished inside or outside. The only other style I've seen is a triangular hole design and it's the same spec otherwise. Unfortunately I no longer have any of them on hand to measure, but they're significantly thicker than the OEM steel wheels.

Richard

 

[Orpedcrow]

This is such a cool truck. Love the cut up roll back bed or whatever it’s from.

 

[BruiserCruiser]

I want one of these really bad!

 

[Supercharged111]

I want one of these really bad!

Take a number. I recently decided if I can find one (crew cab), in any not wrecked not rusted condition, I want it. You can't beat that 15k GVWR. I'd Duramax it and make it 4wd.

 

[motas02]

This is such a cool truck. Love the cut up roll back bed or whatever it’s from.

Nailed it..