Diesel 6 lug to 8 lug

[Luke(MI)]

Found a diesel to trade for my tahoe but its a half ton. 14bt semi float. How hard would it be to convert to 8 lug front amd rear?

Sent from my toilet

 

[great white]

Rear axle is just swap in an 8 bolt of your preference.

Front is a considerably harder, but can be done. Problem is you have a 1/2 ton frame and not a 3/4 in the front. Upper a arm mounts, knuckles etc are different.

My advice?

Don't swap if it's a 6.5, nothing but trouble and you'll only get around the same mpg as a gasser 350. 1-3 mpg better at best. About the same performance too.

There's also very little room for perf improvement if that what you're thinking. An IDI diesel is not like a DI diesel. You can't just pour more fuel and air at it and get big hp/tq. TAkes serious cash to get over the 250 hp mark in a 6.5 and then you're flirting with sudden engine death syndrome (SEDS).

The 6.2 was originally designed as a NA 110 HP (ish) mpg getter in the early 80's and never intended for more than that. Just the OEM turbocharger GM slapped on there adds 3/4 more (nearly double if you believe the 215 hp floated by the internet experts) to that number.

Even in stock form, a 6.5 TD was/is overstressed and GM knew it. They jammed a turbo in there to try and keep up with the other OEMs until they could develop a more competitive solution (otherwise know as the LB7).

If you MUST have a 6.5, skip the 1/2 ton variants and find a 3/4 ton with the 8600 GVWR option. The 8600 GVWR trucks actually are "true" 3/4 ton trucks without any of the 1/2 ton crossbreeding they were doing. IE: 8600 = 3/4 suspension, rims, cooling, L65 engine, frame modulus strength, etc.

Avoid the 506 blocks between 96 (ish) to 98 (ish). Lots of issues that are instantly terminal when they go.

And when they go, they go in a BIG, noisy, spectacular, expensive way....(SEDS)

Think "heads, block, crank" letting go kind of expensive. Big chunks of heavy cast iron flying around in the crankcase kind of expensive.

Ive seen it happen several times and experienced it once myself.

And when mine went, it was one of the generally accepted "best" OEM/GM 6.5 castings; the 599 block. Caved in a piston crown and took out the main webs at the same time.



1st engine: OEM 506 block. Replaced under warranty by first owner under 100,000 kms (cracked #8 cylinder)
2nd engine: Replacement OEM engine (506 block, first owner again) died just over 220,000 kms (cracked at the main cap registers, main webs came adrift and broken crank)
3rd Engine: "Professionally" rebuilt 599 block. Installed by second owner who bought truck with teh dead second engine. 599 died at 402,000 kms (main webs let go and stove in #3 piston crown)

4th engine: I (third owner) now run a $7,000 AMG/GEP 6500 Optimizer block.



For reference as to what you could be looking at, literally EVERYTHING under my hood of my 98 except for the inner fender wells, brake master, the antilock unit, coolant bottle, air cleaner box and some wiring harness has been replaced.

EVERYTHING

Injection pump, filter manager, injectors, turbo, engine, alternator, radiator, clutch fan, vacuum pumps, boost solenoid, all the sensors, fuse box, water pumps, pulleys, etc, etc......all because they failed at one point of another. It's a new truck on an old frame now.

That's what a 6.5 TD does to you. They're the trucks you love to hate.



About the only positive things I have to say about the old wretch is the 4L80E and the 14 Bolt FF rear axle seem nearly indestructible.....

And: that the GEP 6500 Optimizer runs "as sound as a pound". But that's not a GM engine anymore. It's redesigned and improved by GEP, cast by Navistar and hand assembled in the GEP plant in Franklin, Ohio.

Oh, and lets not forget: you have to spend $7,000+ to get one.

 

[GMC Burbalade]

As stated, the rear is easy. The front... not so much. If you want to convert to 8 lug, you'd be better off with a SAS than trying port the 1 ton IFS to a 1/2 ton frame. Shocks, lower control arm, and center link are about the only things that line up.

 

[Jorge6.5]

I had '96 k2500 and worked it hard hauling and towing the motor never gave me a problem ran great when I got rid of it. 250k miles original everything under the hood. Problems I had with the truck, the tranny blew, the 15bff blew and the t case was pretty much cooked.

Like said they can get good economy and with right mods can actually hold up well. In my opinion not worth converting to 8 lug. Run it as is. Remote mount the pmd. Add a better flowing turbo and exhaust.