Project "CREWMAX" Just another crewcab build....

[6600DURAMAX]

Finally decided to post my build thread.

71 4x4 Crewcab Longbed with Duramax/Allison Power Train

Cab is currently at the body shop getting the extension treatment. Hope to have it back by May or so.

Just picked up a 2002 Duramax for powertrain, interior, etc..

Have a couple immediate questions

1. Should I use a factory 71 Chevy 4x4 Frame and just extend it. Worried about the strength? Could box the entire frame. Using that frame would require building all new mounts for everything.

2. Use a 2001 or newer HD frame, everything would bolt in and just re-do the cab mounts. Am really worried about how much of the frame would be seen as those trucks seem to have a ton of frame showing below the cab and it looks like crap. Maybe I could lower the cab as mush as possible.

3. Couldn't I use the 2002 factory wiring harness and just splice in everything, lights, etc..... Plan on using the factory dash, steering column etc..

Any one have any pics of these bodystyles on newer frames

[6600DURAMAX]

No thoughts or comments?

[NurseBen]

Originally Posted by 6600DURAMAX

No thoughts or comments?

Like it. I'm almost done with a frame swap and with all the searching not many had positive thoughts about swapping the frames. The biggest concern was all the alignment of the new body mounts, the wheel base, etc. My thought is if you're daring enough to even think about this swap then fabing up body mounts is the least of your worries. I would think the stock frame is way too flimsy then a fully boxed newer frame. As for the height of the cab I got creative with the frame height and the cab floor, sits very low now, almost too low for the AWD. Looks like a great project.

[Hart_Rod]

Nice

[Dieselwrencher]

Sweet project you are building! My thoughts on a frame swap from a newer GM truck is they look ugly, and out of place under these trucks. (This is just my opinion) They can be made to look ok by hiding it with some step tubes and stuff, but still not ideal. My personal opinion is to start with a cab and chassis 156" chassis or a C30 133" chassis and stretch it to fit your needs. These are the heaviest pick up frames and will take the torque and power. Boxing can't hurt but is some additional work.

Here is one I saw the other day. I just can't get over seeing the entire frame under the truck.
https://www.youtube.com/watch?v=mA9TZC4vsX0

Here is a build thread of another one I remember.

http://www.competitiondiesel.com/for...hlight=duramax

[67ChevyRedneck]

Very cool.

This guy did just what you want to do (but I think it was a 1999+ 1500 Chassis). Frame swap starts around page #9

http://67-72chevytrucks.com/vboard/s...hlight=FRANKIE

[Dieselwrencher]

Originally Posted by 67ChevyRedneck

Very cool.

This guy did just what you want to do (but I think it was a 1999+ 1500 Chassis). Frame swap starts around page #9

http://67-72chevytrucks.com/vboard/s...hlight=FRANKIE

That's not really a good comparison. He's wanting to use a HD chassis, not a 1500. From everything I've seen, the HD frames have more droop under the cab than the 1500's.

[6600DURAMAX]

Continuing to watch all those videos and still contemplating but I am leaning toward just using the older style frame and boxing it. Much cleaner look in the end I believe. Now to just decide if I should use the 1/2 ton frame or find a 3/4-1 ton frame. Anyone know the specs differences between them?

[6600DURAMAX]

Thanks guys for the links above, now to make some decisions and get my body guy moving on the cab!!!

[Pick]

My neighbor built a '68 GMC regular cab on a 2006 2500 HD chassis.

IIRC, lowering the cab to cover more of the frame wasn't terribly difficult but lowering the bed would've required raising the bed floor if he used a standard bed. (he didn't) I'm not sure how adding the crew cab would affect the ability to lower the cab either.

Anyway, it might help you get some more ideas.

He posted a series of u-tube videos about the conversion.....

Here's part 10 Frankentruck HD

[6600DURAMAX]

Pick - That's funny, I watch about 6 or 7 of those last night around 10:30 or so after some of the guys above gave me a few different links. I have a bit to decide but am on the look out for both frames at the moment. Really like the idea of the older frame but do believe it would be nice to start with a 3/4 or 1 ton as I am sure they are taller/thicker and a little beefier. Will be doing some investigation this weekend between crossmember sizes etc..... Might just box the old frame and see about using the factory crossmembers if they are wide enough? A lot to ponder....

[SS Tim]

IMHO for building a period crewcab with an 8' or 8 1/2' bed the best choice would be a hybrid frame using a 157" C30 frame and splicing in a C30 133" rear to maintain the factory top line thus a facory bed installation.
As to reference numbers this is my latest frame specs blurb.


The 67-72 frames are not exactly the same except the K10 LWB and K20.
These are the different PICKUP TRUCK frames as I understand.
Referenced from the GM 1970 truck engineering specifications book.
Any corrections are invited.
SS Tim

C Blazer COIL
C/10 115" COIL
C/10 115" LEAF
C/10 127" COIL
C/10 127" LEAF
C/20 127" COIL
C/20 127" LEAF
C/30 133" LEAF (Longhorn C/20 & C/30, 9' Stepside)
C/30 157" LEAF (Chassis Cab only) included for reference
Note: The 157" frame kicks up a little higher than the 133" going over the axle and does not drop back down like a 133" or 127"


K Blazer
K/10 115"
K/10 / K/20 127"

The frame section and modulus numbers, 39k psi carbon steel through C30s. Note the increased section height, flange width and thickness changes of the frame as the series step up.

C Blazer
C10 115"
C10 127"- 6.04" section height, 2.53" flange width, 0.156" thick, 2.98 section modulus

C20 127"- 6.11" section height, 2.46" flange width, 0.194" thick, 3.71 section modulus

C20/30 133" (Longhorns)- 7.20" section height, 2.77" flange width, 0.194" thick, 5.05 section modulus

C30 157"- 8.18" section height, 2.97" flange width, 0.224" thick, 7.29 section modulus


K Blazer
K10 115"- 6.02" section height, 2.71" flange width, 0.141" thick, 2.70 section modulus

K10 127"
K20 127"- 6.09" section height, 2.75" flange width, 0.186" thick, 3.48 section modulus



http://67-72chevytrucks.com/vboard/s...95&postcount=5
http://67-72chevytrucks.com/vboard/s...2&postcount=12

[6600DURAMAX]

SS TIM - Man cannot thank you enough for all that info.... That is some great information and a lot to digest.

I do believe I see your point in using a 157'' then splicing the 133'' rear section but looking over the info below I am curious if the 157'' frame eventually tapers to the same section height of the 133'' at some point???

Utilizing the 157 would give the crewcab plenty of flat frame section then the 133 would allow a long bed to match up nicely with the correct step up.

As far as boxing a 1/2 ton frame, would the section modulus double in that regard?
While boxing the frame does take some work, finding two separate frames could be pretty difficult also.

Thanks, appreciate all the input

[SS Tim]

Originally Posted by 6600DURAMAX

SS TIM - Man cannot thank you enough for all that info.... That is some great information and a lot to digest.

I do believe I see your point in using a 157'' then splicing the 133'' rear section but looking over the info below I am curious if the 157'' frame eventually tapers to the same section height of the 133'' at some point???

Utilizing the 157 would give the crewcab plenty of flat frame section then the 133 would allow a long bed to match up nicely with the correct step up.

As far as boxing a 1/2 ton frame, would the section modulus double in that regard?
While boxing the frame does take some work, finding two separate frames could be pretty difficult also.

Thanks, appreciate all the input

Hope it all helps and isn't TMI!
As to the matchup, I don't have a full profile map of either frame to say for sure but it may very well be close at some point.

Given the thickness of the flanges on paper it looks like the 133" frame will be about 0.53" shy of nesting inside the 157" at full section height. To me, nesting against the top flange and pie cutting the lower flanges would be the solution. Then finger tabbing the upper and lower flanges as runouts.
Here is a thinking out loud sketch.

Boxing or section increase is your choice but I think using the taller factory section and selective plating/fingering/boxing is probably best.

[Dieselwrencher]

Last I knew, Cypressbog in Wisconsin has a 133" frame and cab he's trying to sell. I had a line on 2 157" frames but I guess the guy scrapped them. A day short on that.

http://www.67-72chevytrucks.com/vboa...d.php?t=718852

[Lokin4AReason]

this should be an interesting build ..

[mjensen]

I'm in! Done yet?

[6600DURAMAX]

Thanks Dieselwrencher I sent him a PM about it

[6600DURAMAX]

What about a C50 frame? Do they have the same body mounts for the cab/front clip? Just curious because there have been a few I have seen for sale. Just Curious

[Dieselwrencher]

I am not for sure, but I think the C50 frames are more of a C channel frame. You could probably use it. I'm planning to on my next build. Hopefully

[BlueBullet]

I have a 1972 C50 that is from SD that I would sell the frame off if you decide to go that route. I think it is a 157" wheel base.

[6600DURAMAX]

Looks like the C50 frames are mostly flat, I think I'll pass on that option.

SSTim - you mentioned that the 157" frames kick up higher over the rear axle than the others, any idea how much additional? As this will effect the final bed height and might require me to shim the cab higher to match the body lines. Any idea of that measurement?

Thanks guys

[SS Tim]

Originally Posted by 6600DURAMAX

...SSTim - you mentioned that the 157" frames kick up higher over the rear axle than the others, any idea how much additional? As this will effect the final bed height and might require me to shim the cab higher to match the body lines. Any idea of that measurement?...

Yes, I posted this link,
http://67-72chevytrucks.com/vboard/s...95&postcount=5

along with the data I have in post#12
http://67-72chevytrucks.com/vboard/s...2&postcount=12

[lower50's]

Cool build!! What is the biggest challenge to get the body lower on the 2500 frame? Width of the frame or the shape?

[Rednwhitec20]

Love me a duramax swap, and a crew too? Dream truck.