Lengthening a C30 157" frame

[CCCC]

Need some "how to" info. Am ready to do an odd project - converting a very low-mileage 72 C30 chassis mount MoHome to a cab+sleeper+long bed 5th wheel hauler. Looks like I need an additonal 24 to 30 inches of wheelbase length to make it work nicely. Anyone know if this is feasible and where and how best to make the insert - or know of any threads that tell/show how best to do this. Any help appreciated.

[SS Tim]

Just to clarify.
You have an existing 157" and you want to strech it to 181-187"? What bed are you wanting to use, an 8' or 8 1/2' longhorn bed?
A stock 157" will give you 30" between the cab and an 8' bed.

Been playing around with a 10' bed concept on a 157" with the rear bobbed to SWB overhang (8.14"). Though it might end up a 9' on a 145" due to California's definition of "pickup".

As to doing the mod. Everything I have found here has been on shortening. But many ramp trucks and some motorhomes were on extended chassis so hopefully someone can give use some pictures and fishplate sizing info.

Thinking that for what you want another chassis might be the best way to add the length. A section extendending forward from the carrier bearing on the added section to aft of the existing carrier bearing crossmember. Then you can run a three piece driveshaft with two stock sections. Remeber though a 133" is different from a 157". PM an email for this drawing that may be helpful to you.

The crewcab GMC pictured would be about a 166"wb.


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

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

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


http://67-72chevytrucks.com/vboard/s...d.php?t=545240

[propanemudtruck]

Hey There - if you had access to another C30 frame, you could cut two frames long and join those together instead of trying to splice an extension in the existing frame.

[CCCC]

SS Tim - thanks - I appreciate your data. We basically are are on the same track. Current wheelbase is 157" and want to use an 8' bed - am thinking about at least 48" (interior) sleeper compartment behind the cab. Our thinking on added length is about the same, but my calcs only give me 27" from back of cab to front of 8' bed on the 157" base. I need to take another look/measure.

Have not ever seen such a MoHome on a longer chassis, but have seen two haulers like that - so - it has been done nicely. I just want to get it right by using someone's good experience. The aded driveshaft issue seems to bother me the most, so thanks for those observations.

Please chime in with anything else you think about, and please see PM on this.

Propanemudtruck - thanks. am looking for a junked C30/GM3500 frame. The other 1 tons here are too nice to tear up.

Anyone else out there?

[CrewCab59]

If don't care you could use a newer P30 step van frame build or transfer the body mounts over , most were 156wb and 186wb plus the extra 2 to 3 over hang. That way no worry about cutting the frame, just a thought.

[da-burb]

My 71 C30 Motorhome is a stock 157" stretched to 184"+/-. They butt welded a section of C30 frame and then put a piece of 1/4" plate half way inside the frame and spot welded that in. The plate is about 10" longer than the stretch.

[uncle]

Gotta ramp truck that's about 200" wheelbase. Never driven it but will look and get apic or 2.
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[SS Tim]

OK, Glad to be of help.
Ran through the numbers and this is how I am getting a 30" gap on a 157"wb with an 8' bed (which actually measures 98" inside length and 102.23 overall length).

127" w/8'bed
133" w/8 1/2'bed, 6" longer bed forward of the rear axle (Longhorn)
157" - 127" = 30" wheelbase stretch/increase from rear of cab to bed front panel over stock gap.

The crewcab picture I posted earlier is probably a 169"wb.

Scott-Bilt crewcab is a 42" stretch as a point of reference.
Their frames were extended and fishplated

Here is 68 C30 178" wb ad link
http://67-72chevytrucks.com/vboard/c...l-texas&cat=12

[CCCC]

Originally Posted by da-burb

My 71 C30 Motorhome is a stock 157" stretched to 184"+/-. They butt welded a section of C30 frame and then put a piece of 1/4" plate half way inside the frame and spot welded that in. The plate is about 10" longer than the stretch.

Thanks - hope you can reply some more. This is good - since that altered WB is 184 -where did they cut and splice the frame?? What did they do to lengthen the drive shaft arrangement? Add another section with another carrier bearing or just universal joint, or lengthen one original section?

[CCCC]

Originally Posted by uncle

Gotta ramp truck that's about 200" wheelbase. Never driven it but will look and get apic or 2.
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Thanks. Wow - 200". I will appreciate anything you can send - pics or data on how it was done.

[CCCC]

SS Tim - thanks for your interest and info. It is clear how you are getting the 30" gap.

I have been using somewhat crude measurements (quickly today, out in a freezing garage) and got front of 8' bed to middle of rear wheel at 60" and back of cab to middle of front wheel at 73" for a total of 133" and a resulting gap of only 24". So, there is a 6" difference in our calcs, and am figuring that you are more on the mark - which would be good because I would need to add a bit less splice. I will get that nailed exactly on this truck.

The data on other conversions etc, is helpful and the info from some other guys here is also interesting - like using a "P" frame - but I want to try to keep this project as simple as possible so don't want to move this rather cherry cab and drive line.

I need to find part or all of a C30 frame and, looks like, some drive shaft stuff. I live very remote, so finding old stuff is hard - it's many miles away. Maybe I need to get that one in OK. Oh well, it's only time and $$, right?

Thanks again.

[PAWS 72]

google big truck sleeper and call a couple of them. the will give you the lenght of splice that you will have to have.

There is several guys that haul campers that has them on their 3/4&1 ton trucks. I wanted one but never did have 1 installed. $6500.00 for a new one the last time I called about 3 years ago.

I found a 48'' sleeper last year i should have bought.It came off a friend's big truck when it got rolled on the side.

[SCHRUMGMC]

Them Extended things look weird to me LOL

[PAWS 72]

had to switch puter. Check these out.The Ford,The guy paid close to $30,000.00 for it installed in Shipshewana, Indiana. It's an 8' condo for big trucks.The fuel mileage changed by 3 mpg.I used to see the guy alot when I was going up there.

I would tell a story about me and him coming home one nite but this isnt' the thread.Highspeed thru Montgomery ala. The other I talked to the guy some on the yard. Never did see a Chevy tho.

[OldCreek]

I suppose you could add the length to the rear of your frame and slide the axle back. You will have to move the leaf spring mounts, etc. The 4x4 guys do it all the time...not too difficult at all (if you like removing rivets!).

You will, however, have to lengthen the drive line, e-brake cables, fuel line, brake lines, rear light lines..I'm sure you know all this. You're pinion angle may be off, also. Still, these are things you will have to do if you cut and splice the frame, too.

...Sounds like fun!

As SSTIM posts, the frame section is definately larger in the 157" wheelbase.

[SCHRUMGMC]

How in the world is these mutations even made?

[GASoline71]

Steel, a welder, and some imagination.

Gary

[SCHRUMGMC]

Do some of these come from Production ?

[72 tigger]

I built a 149" WB extended cab by using two chassis. That way there was just one splice. I would recommend cutting the frame in a Z pattern, instead of a butt splice (a 1/4" fish plate on the inside is a good idea also). A drivetrain shop should be able to help with the driveshaft problem.

[Dieselwrencher]

Originally Posted by SCHRUMGMC

Do some of these come from Production ?

Only production would be from a fab shop or conversion shop. These are popular with hot shotters for the most part.

[SCHRUMGMC]

Oh okay, I have never seen anything like it !! LOL..

[CCCC]

Originally Posted by OldCreek

I suppose you could add the length to the rear of your frame and slide the axle back. You will have to move the leaf spring mounts, etc. The 4x4 guys do it all the time...not too difficult at all (if you like removing rivets!). You will, however, have to lengthen the drive line, e-brake cables, fuel line, brake lines, rear light lines..I'm sure you know all this. You're pinion angle may be off, also. Still, these are things you will have to do if you cut and splice the frame, too. ...Sounds like fun! As SSTIM posts, the frame section is definately larger in the 157" wheelbase.

Good observations - and - due to the MoHome configuration, that frame already has been extended further behind the rear axle, so I do have the frame capacity back there. But, as you note, it's a pain (for me, anyway) to bust rivets and move the entire axle assembly - not going to do that - and, enough other stuff to extend already. Have yet to decide between pickup bed or flat bed back there - but the flat bed config would make things quite a bit simpler. Size of sleeper is in the mix as well. Must make some decisions because I want to move it out and get the project started in less than 2 weeks. But, as you said, it is fun.

[brad_man_72]

I build driveshafts for a living, I've built thousands for 10' stretch limos, and other assorted stuff. Unless you like moving crossmembers around id add the frame lenght between the trans and first carrier mount. That way the driveline shop only needs to build one carrier shaft. The driveline shop will need to ballance all 3 shafts together in one ballancer, if they can't do that take it somewhere else.

We work with quite a few big rig shops/rebuilders and limo builders, from what I hear some of the big rig shops charge next to nothing to lenghten a frame, and have a good working relationship with a driveline shop. They will also be able to rivet anything back together so it looks factory. This may be a good cheap and fast option!
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[CCCC]

brad_man, this is very helpful info. The drive shaft insight is excellent. Have not yet decided whether or not to lengthen the frame and don't live anywhere near a big rig shop, but can get to one if needed.

[uncle]

Can't tell if 2 frames or stretched but is 200" wb. It's plated from back of cab and goes about 4ft. May be able to see in 1st pic. It also has extension in rear. Has one stock x-mem and one added so it has 3 pc. shaft. Here's a couple pics.
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