Starting a Suburban build.....

[ntsqd]

Doesn't sound like a 60 up front is in plans or desired, so the steering will be totally unaffected and won't even be disturbed by an 8 lug swap.

 

[John90XJ]

I think a D44 is perfect for what I want to do. I'm not even sure how often 4wd would be needed but having that functionality is nice.

 

[ntsqd]

What you have now should be a GM 10 bolt. No real functional difference btwn them, i.e. not worth the trouble of finding & swapping a D44 to replace the 10 bolt just to have a D44. D44's came in the older trucks.

 

[John90XJ]

So you're saying there are 8 lug 10 bolts? I thought I needed a D44 to get the 8 lug to match the 14 bff in the rear?

 

[ntsqd]

No, you only need the stub spindles, wheel hubs, wheel bearings, rotors, and caliper brackets to convert your existing 10 bolt to 8 lug. Should be able to get those off any 3/4t donor.

http://coloradok5.com/8lugconversion.shtml

One thing to note though, some of these real late 'box' trucks used a different front caliper, so you may need to swap them too. I believe the calipers that don't work only came on the 3/4t Subs, but a heads-up in case you do run into this.

 

[Grim Reaper]

No, you only need the stub spindles, wheel hubs, wheel bearings, rotors, and caliper brackets to convert your existing 10 bolt to 8 lug. Should be able to get those off any 3/4t donor.

http://coloradok5.com/8lugconversion.shtml

One thing to note though, some of these real late 'box' trucks used a different front caliper, so you may need to swap them too. I believe the calipers that don't work only came on the 3/4t Subs, but a heads-up in case you do run into this.

Hold on!

Waxer (Steve) changed the spindle becasue he was converting a 1974 D44. He used a 10 bolt spindle becasue the D44 actually used a smaller bearing. I am pretty sure when he ordered the parts they were for a 79 3/4 ton and that was a 10bolt that year. I think you just need the hub on 10bolts newer then about 79 and he even mentioned that.

Steve and I talked a lot about this when he did this and spant a little bit of time looking up part numbers to figure out what really needed changing.

 

[ntsqd]

AIR my '91's spindles were nothing like my 79's.

 

[John90XJ]

But in the long run, to facilitate the gearing change, it would likely be easier to swap axles after finding a pair that match and will drop right in.

I thought about making changes to the front axle but by the time I match the gearing to what I put in the rear it would be cheaper to just replace the entire thing.

What about other mods? Anything I should be looking for in skid plates, armor, etc?

 

[ntsqd]

Sure. How much do you want to spend?

I've been cautioned that the 10 bolts bend if used hard in desert race chase mode. Hasn't happened to me yet, but a truss might not be a bad idea with Baja roads in mind.

cK5.com has a wealth of knowledge on these trucks.

 

[John90XJ]

So I crawled under it last night and it appears to be a 10 bolt at each end (round covers and 10 bolts visible). Are there any stampings or tags that are not glaringly obvious to tell me the gear ratio? I know I can jack it up and turn the driveline and count revolutions but hey, this is the Pacific Northwest....I'm gonna get soaked doing it.

 

[ntsqd]

Grim has more depth here than I, but I think there should be a tag under one of the bolt heads with some sets numbers stamped in it. Unless it/they were lost by someone doing an inspection, or b/c the ratio was changed.
If they do exist one of those number sets should look something like "3.73" or "41:11"

 

[Grim Reaper]

DANA was good about putting the tag on a bolt but to be honest I have never seen a tag on a Corporate.

Stuck to the inside of the glove box will be a sticker with a bunch of 3 digit codes. That is the RPO codes that tell you everything about the options on the truck. One of those will tell what gear ratio the truck came from the factory with. Gear ratio usually starts with "G" or "H".

http://www.chuckschevytruckpages.com/rpo_codes_1973-87.html

 

[John90XJ]

Stuck to the inside of the glove box will be a sticker with a bunch of 3 digit codes. That is the RPO codes that tell you everything about the options on the truck. One of those will tell what gear ratio the truck came from the factory with. Gear ratio usually starts with "G" or "H".

http://www.chuckschevytruckpages.com/rpo_codes_1973-87.html

Found a "GT4" so I guess it's 3.73's. At least I could run 31s without doing anything and then plan the rest of the build this winter and start a pile of parts in the garage. Thanks for the insight.

 

[Grim Reaper]

Found a "GT4" so I guess it's 3.73's. At least I could run 31s without doing anything and then plan the rest of the build this winter and start a pile of parts in the garage. Thanks for the insight.

Sounds like it has the HD tow package. Does it have an oil cooler? I bet there is also a G80 RPO. That's the factory locker and honestly if you don't thrash on the truck it is a decent working locker. My 79 K5 had one is it really did a good job.

Now you hammer on them with a lot of wheel spin on one wheel and it catches it will earn its nick name "Grenade locker".


The truck will clear a 32x11.5 (or 265x75x16) on a 8 inch rim with no mods. 33x10.5 will probably fit as well. 33x12.5's will fit with a little trimming and hammer work on the lower fender lips.

 

[ntsqd]

I'm fitting 285's on the later OE alloys with the above mentioned springs and no body work or rubbing.

I have 3.73's too. With that tire I'm pondering going to 4.11's. The truck pulls it, but on grades I can tell I'm working the trans pretty hard just towing my little trail-tent trailer.