55.2-59 subframe question

[jmlloar]

Thats on chevy.
55 to 57 gmc uses the 57 chevy fenders.

[mr48chev]

I wouldn't have thought that a 56 used a core support similar to the 47/55.1 trucks.

That would be an ill driving mess with that axle on backwards.

[jmlloar]

axle is not on backwards.
tie rod is flipped from rear to front.

[mr48chev]

Originally Posted by jmlloar

axle is not on backwards.
tie rod is flipped from rear to front.

Why would anyone be fool enough to do that and mess up the steering? That will throw the ackerman way off and cause the tires to not track right on turns unless you modify the steering arms correctly to make it right.

Rat rod stuff maybe but not something that one wants to drive right and go around a corner without dragging a tire.

[jmlloar]

Originally Posted by mr48chev

Why would anyone be fool enough to do that and mess up the steering? That will throw the ackerman way off and cause the tires to not track right on turns unless you modify the steering arms correctly to make it right.

Rat rod stuff maybe but not something that one wants to drive right and go around a corner without dragging a tire.

That will not mess with Ackerman angle.
If so there sure are alot of 4x4 pickups with solid axle that are screwed.

I'm not going that route anyway. Thats why we're discussing the frame splice.

[mr48chev]

Originally Posted by jmlloar

That will not mess with Ackerman angle.
If so there sure are alot of 4x4 pickups with solid axle that are screwed.

I'm not going that route anyway. Thats why we're discussing the frame splice.

Simply because 4x4 trucks with the tie rod in front with FACTORY steering arms have steering arms SPECIFFICALLY designed to take that factor into account. The correct geometry is designed into them. As correct as it can be but we all know and understand that solid axle 4x4 rigs eat front tires up o chew them up too. Even my 92 Ranger with the swing axle thingie is hard on front tires. That truck has lock out hubs and gets driven in two-wheel drive form most of the time.

I've delt with a number of T buckets and hot rods that guys reversed the steering arms to the front like that and the issue is always the same, When they go around a corner one wheel doesn't track right and drags or pushes. it isn't all that noticeable with T buckets with rather skinny front tires except for excess wear for the miles on the tires. it becomes a real issue with rigs with wider tires

If you were trying to do a cross steer with a two-wheel drive C-10/20 box you would have been far better off to build, adapt, or modify a steering arm to attach to the right-side spindle and maybe run off the top bolts. That way you wouldn't actually change the steering geometry.

[dsraven]

is that an old impala parked next? I would like one for my next project, wife. not so much, haha

[jmlloar]

Originally Posted by dsraven

is that an old impala parked next? I would like one for my next project, wife. not so much, haha

bel air 2dr sedan

[dsraven]

the tie rod scenario probably has something to do with the power steering box mounted to the outside of the frame. it likely doesn't turn very sharp to the right before the tire rubs. the plan is to splice in a working independent suspension.
I have seen pics of the GMC style rad support but never seen it in person. it seems similar to the AD trucks but more flexible. would the plan be to keep that set up or have a less flexible set up? since the fenders and hood are bolted to the cab it seems like a lot of ability to move at the front would put strain on the fender mounts and hood latch/bumpers. I know it has lived this long like that but just spit balling since we all strive for smaller gaps and better fitment of the body parts than factory.

[jmlloar]

the gmc uses rods from the firewall to rad support to stiffen it.
I would thonk the chevy would be worse gap wise since the rad support is held tight to the frame on both ends making it flex with the frame, where as the gmc is only held in the center allowing the frame to twist under it while keeping it in in line with the cab. My gap change should show at the bumper to grill area when the truck flexes instead of twisting the sheetmetal.

I flipped the complete tire rod assembly for oil pan clearance. I moved the engine forward about 2in and down about 1in so I didnt have to cut into the firewall. cut the drag link part off of the steering assembly so it was no big deal to put it on backwards. That idea is going anyway. Now it will be either a front clip or complete frame from 73 up. either way frame needs cut since the wheelbase is diff between the two.

[jmlloar]

the turning radius was the deciding factor. Dont know how much you guys with half tons lose but the newer 16 wheels with the front mount box gives me 2 directions left or straight ahead. and that is with 1 1/2 in wheel space per side.

[jmlloar]

Just a little bit of trivia.
5.3 chevy, 4l80e with fixed yoke, 99 semi float 8 lug gm rear and I'm still using the factory 55 drive shaft with the factory 55 yokes, shortend a little on each side of the carrier bearing. original size ujoints and carrier bearing. And the factory 55 spring saddles on the 99 rear original 55 springs. I only needed new center pin bolts to refresh the springs. and new spring perches for the 99 rear.

Gotta love how gm used what worked good and didn't change it.

[dsraven]

probably right about the gmc versus chevy rad support mounts. too late for me now, my rad support is built already with the mounts on each side.
maybe the later chevy steering box works on a lifted 4x4 where the tires would clear, not so great on a more stock height truck. lots of guys have got around that by modifying a box from something else bolted to the side where the original box was, so the output pitman shaft is in the same place.

[jmlloar]

Originally Posted by dsraven

probably right about the gmc versus chevy rad support mounts. too late for me now, my rad support is built already with the mounts on each side.
maybe the later chevy steering box works on a lifted 4x4 where the tires would clear, not so great on a more stock height truck. lots of guys have got around that by modifying a box from something else bolted to the side where the original box was, so the output pitman shaft is in the same place.

Was going to do the cpp kit in stock location but the steering gear is on back order estimated delivery of over 6 months from now. not to mention the $600 price. can get frame clip for less than that.

[dsraven]

the newer style box in the old loaction is very close to a V8 exhaust anyway.
I seen a TF truck on a 88-98 truck frame and it fit pretty well. it was on this site. thats a whole frame swap though so more headaches appear as you continue on. my 57 is sitting on a GMC envoy frame and running gear. way to low for somebody who wants a stock height look. kinda low for me too since I used the floor and firewall from the donor. there are guys who do a more stock height though. lingefelter did a 55 on a trailblazer frame, the Erod, if you google it you can see it.

[jmlloar]

Originally Posted by dsraven

the newer style box in the old loaction is very close to a V8 exhaust anyway.
I seen a TF truck on a 88-98 truck frame and it fit pretty well. it was on this site. thats a whole frame swap though so more headaches appear as you continue on. my 57 is sitting on a GMC envoy frame and running gear. way to low for somebody who wants a stock height look. kinda low for me too since I used the floor and firewall from the donor. there are guys who do a more stock height though. lingefelter did a 55 on a trailblazer frame, the Erod, if you google it you can see it.

I thought about newer but the frames get less straight as you get newer.
Got access to a 90's 3500hd but kinda wide with I beam axle and 19.5 wheels. Also got a 91 3500 but it to has alot of bends in it. To do the splice I need a 64 to 87 with 73 up being the best choice.

[dsraven]

have you seen "project Tow-Rat (Lil'Blue) in the projects secton. he used a 1 ton front end on his. he built his own frame, really nice job, but the idea is there for you to see what he did. he is using ton wheels so there is a spacer on the hub to get the wheel where it needs to be, like a regular 1 ton wold have but possibly not as wide of a spacer? ! ton wheels may clear the steering box better, dunno the track width but the tires fit inside his fenders. I seem to remember one that had the cross member narrowe
d. Can't seem to access the code for that memory though, haha.
SGTUSMC is the guy with the 59 on the 88 frame. his is lowered I think though. it would maybe show the bump in the frame and maybe what he needed to do to get it under there. possibly if you don't want it on the ground the frame bump would be workable?
just ideas for you to look at. sometimes seeing how somebody else did something makes you think of a new way to do something on your project. you can search the site for that members build if you think you wanna see it.

[dsraven]

have you seen the gm upfitters site? they have frame drawings from a lot of years. light duty prior to 2013 is a listing there. maybe find some drawings with the GM specs. try the bodybuilder manual on the site and follow to the area you need to go to.

[dsraven]

quickly looking through the sgtusmc build there is mention of a guy who put a 4x4 frame under his task force and it was high enough to clear the step on the box with the front spring mount. I wonder if it would work if the body was spaced off the frame tall enough so it didn't hang down below the body but almost, like a newer truck has. these frames have a pretty flat rea section by the look of it in that thread. the body builder's frame drawings may help figure that out if interested. upfitters has a lot of info there to peruse.

[Nima]

I don't know if this was mentioned or not but why not just graft the complete front crossmember with all the suspension and steering component to the stock frame instead of the whole front clip from later model truck? That is what I wanted (and still want) to do with my 3/4 ton but since it seemed to involve for my skill set, I went another route.

[jmlloar]

Originally Posted by Nima

I don't know if this was mentioned or not but why not just graft the complete front crossmember with all the suspension and steering component to the stock frame instead of the whole front clip from later model truck? That is what I wanted (and still want) to do with my 3/4 ton but since it seemed to involve for my skill set, I went another route.

This wont work. the 55 to 59 frame is the same width front to rear, the 73 up is a lot more narrow in front of the cab to give room for independent suspension.

[mr48chev]

[QUOTE=Nima;9045394]I don't know if this was mentioned or not but why not just graft the complete front crossmember with all the suspension and steering component to the stock frame instead of the whole front clip from later model truck? That is what I wanted (and still want) to do with my 3/4 ton but since it seemed to involve for my skill set, I went another route.[/QUOT

The main reason is that the TF frame is just over 34 inches wide at the front axle They are pretty well true "ladder frames" as they don't vary in width front to back enough to get excited over.

At the front axle line 60 / 87 full size trucks all run just over 28 inches wide outside of frame rail to outside of frame rail at the axle. Just enough so that with a spacer plate you can slip the frame off a 47 second series though 55 first series rightdown between the rails. A guy in Cali did a bunch of AD trucks with I'm thinking 64/66 front suspenson back in the 1980's.

We had a guy show up with the worst case of cobbled together TF with mid 70's square body front suspension and maybe the worst case of cobbled together chassis I have ever seen in All my years of being around modified rigs. A section of the square body frame was scab welded to the inside of the notched TF frame.

Everyone here knows that I am not a fan of frame swaps the sake of being a "cool guy with a frame swap but on this truck for what he wants to do with it I think finding a 3/4 ton donor with a solid frame and good running gear chassis wise. and doing the frame swap is the wise move.

There are a number of reasons that I believe that swapping frames in this case makes more sense.

First ease of finding chassis parts = bushings and suspension pieces.
Second: a rear axle that you can walk into any Napa and still buy parts for without a hassle. No digging into the rare parts file.

There is far less hassle in building cab and bed mounts to get the cab, nose and box level than there is trying to figure out everything to mate the front of the later frame and the back of the older frame together and get it all right.

[dsraven]

ok, maybe just me but, I can't get my head around how you would splice the frames under the cab somewhere and still have the ride height you want, at something close to stock for trailer towing. if the newer frame is dropped down in the middle are you talking about a splice that involves one frame sitting on top of the other frame? that would keep your cab mounts where they need to be but really you could just use the complete frame from the newer truck, build new cab mounts to space the cab off the frame to where it needs to be, and shorten the rear section for where your axle centerline needs to be.
or, buy some rectangular steel lengths and build your own frame using dimensions from the assembly manual and the upfitters frame drawings. kinda like what lil tow rat has done, even if you just built the front section so it has a good long overlapping section for strength but then comes together and up to accomodate the front end of choice.
maybe a quick drawing posted would help us help you figure it out or come up with ideas you can use.

[jmlloar]

I'm not that far along yet. I still need to get the newer frame and do some actual comparison. Guesstimating it appears that the 73 up frame will be at least partially below the 55 frame. I'm not building a frame from scratch. just using part from one and part from another. cab is already sitting where it needs to be, this way all I have to do is mate the newer front piece square and at correct position to keep the truck and suspension at correct angles.

This is basically no diff than using a camaro subframe that has been done a million times before. I'm just using a heavier built truck front clip.

Going by pics it also appears that everyone seems to think the 73 up frame drops compared to the 55 to 59. I think this is only partially true. I would say its even amount of drop and rise putting the 55 to 59 about halfway between the two.

Pretty sure mr48chevy hit the nail on the head back at #14

[dsraven]

ok, thats what I was wondering about, the drop offset. if you can get some frame drawings, and a bit of time to get them somewhat at the same scale, you could lay one over the other and really see how it fits before you cut anything. then you can see the best way to go about it all. or, just cut and line up and go from there, box the inside when done-or not since you will have a nice long overlap. those lennox metal cutting discs work really well and don't wear down to be smaller diameter as you go. a plasma cutter is nice if you have one, a torch with a grinder afterwards also works just not as precise unless you like grinding. starting with clean metal is always good.
you alrady knrew that, sorry, don't mean to imply anything like that. just spitballing ideas mostly.
anyway, keep plugging away and posting so we can see how it works out. a few pics along the way.