47-55.1 Cab too low at the rear, any ideas? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

MARTINSR · 02-16-2020, 11:56 PM

Anyone have any ideas on why my cab is low in the rear?

Ok, what am I missing here. I bolted these shackles on the back of the cab. New bushings, it was the proper height. I trailered the thing to my new house (700 miles) and now the cab is a half inch lower in the rear and even hit the running board aprons denting the cab. Glad it wasn't painted! So I jacked the cab up where it belongs and there is a half inch gap to the shackle. Any ideas?

Is there suppose to be a spacer between the shackle and the cab? Is this shackle mounted too low on the frame or something? The holes where there, I didn't drill them.

Brian

nvrdone · 02-17-2020, 01:04 AM

brian: you know tolerances on these trucks were really poor. could be the shackles you got are too short. I solved the problem by adding a piece of 3/4" flat stock on the left side and 1/2" flat stock on the right side with longer bolts to get the cab to sit right. and the frame isn't bent. we do what we gotta do to get these old rigs looking right.

**joedoh** · 02-17-2020, 02:12 AM

do you have the right bolt size? the frame side bolts are supposed to be an exact fit in the frame holes. if you used smaller bolts with a clearance fit, it wouldnt surprise me if it first slipped to the bottom of the clearance fit (small change) and then beat the frame hole ovaled over 700 miles (big change).

same with the upper shackle bolts, should fit the hole exactly, and there is usually a shim on the bottom side, not 1/2 inch. the bolts install from the bottom to the top, with a threaded plate on top.

here is a picture of the set I just took off a 54. the shims are on top, the plates are there, and you can see the shoulder on some of the bolts.

MARTINSR · 02-17-2020, 09:16 AM

Thanks guys, I thought there was a threaded plate "nut" at the top! I don't have it so large washers and regular nuts is going to be ok there. I could make that plate easy enough. Well sort of easy enough, I don't have a lot of my tools like I did at my old house, no vice, I need to get one.

I am thinking it is a little of everything, reproduction bushings too, if everything gives a bit, whamo, there is a bunch of difference.

Brian

mr48chev · 02-17-2020, 06:35 PM

I've got the assembly manual pages here https://s173.photobucket.com/user/mr...?sort=2&page=1

The shackle setup here.

I'm not sure how close that will come on yours though. It may be that shimmed up to sit level the way you want it counts more than exact measurement.

MARTINSR · 02-17-2020, 11:52 PM

I am making shims, I am thinking a little enlarging of the holes a little bending of the floor, a little this a little that, add up.

Brian

mr48chev · 02-18-2020, 02:32 AM

You might want to make your shims long enough to spread the weight out.

I wasn't sure if that was a 48 cab or a replacement but that part looks to be later edition like this 53 floor on one of my cabs.

This shot marked for someone with a 47/48 truck showing that the piece went all the way across.

That is the cab that had the top cut off that is stuck under the shed that fell down.

MARTINSR · 02-18-2020, 09:44 AM

It's a 52ish cab I believe.

Brian

mr48chev · 02-19-2020, 01:16 AM

Should be set up right for the shackles then. I was looking today figuring what it was going to take to dig that blue cab out of where it is and after I get the tin roof out of the way it will be chain saw time.

vintovka · 02-19-2020, 01:28 AM

Got tired of the old, worn out, original cab mounts. Tossed them and went with 1"x 4"x 5" shims made from Choice Deck synthetic decking leftover from my bed and last deck project. Added 1/2" bolts with 2" HD washer to bolt cab directly to frame. No felt difference from the old mounts plus the choice deck seems to have some cushion/vibration damping qualities.
Seems it does not "sway" when turning ether. No signs of stress on cab or mounts either. Squared the cab to the frame this way and no more "butt sag" or touching the running board aprons.

dsraven · 02-24-2020, 08:32 PM

If you are gonna swap the mounts out you might consider energy suspension generic mounts, fab some frame mounts and cab mounts, with extra support, and go with that. Easy enough for an old hotrodder like yourself to figure out. Otherwise, support the sheet metal and them shim as required. On a level floor with a good level on the cab. Trial and error man, you know.

02-16-2020, 11:56 PM	#1
MARTINSR Registered User Join Date: Dec 2000 Location: Boise, Idaho Posts: 6,001	Cab too low at the rear, any ideas? Anyone have any ideas on why my cab is low in the rear? Ok, what am I missing here. I bolted these shackles on the back of the cab. New bushings, it was the proper height. I trailered the thing to my new house (700 miles) and now the cab is a half inch lower in the rear and even hit the running board aprons denting the cab. Glad it wasn't painted! So I jacked the cab up where it belongs and there is a half inch gap to the shackle. Any ideas? Is there suppose to be a spacer between the shackle and the cab? Is this shackle mounted too low on the frame or something? The holes where there, I didn't drill them. Brian Attached Images __________________ 1948 Chevy pickup Chopped, Sectioned, 1953 Corvette 235 powered. Once was even 401 Buick mid engined with the carburetor right between the seats! Bought with paper route money in 1973 when I was 15. "Fan of most anything that moves human beings"

02-17-2020, 01:04 AM	#2
nvrdone Registered User Join Date: Dec 2011 Location: Moxee WA Posts: 1,422	Re: Cab too low at the rear, any ideas? brian: you know tolerances on these trucks were really poor. could be the shackles you got are too short. I solved the problem by adding a piece of 3/4" flat stock on the left side and 1/2" flat stock on the right side with longer bolts to get the cab to sit right. and the frame isn't bent. we do what we gotta do to get these old rigs looking right.

02-17-2020, 02:12 AM	#3
joedoh Senior Member Join Date: May 2007 Location: Doodah Kansas Posts: 7,746	Re: Cab too low at the rear, any ideas? do you have the right bolt size? the frame side bolts are supposed to be an exact fit in the frame holes. if you used smaller bolts with a clearance fit, it wouldnt surprise me if it first slipped to the bottom of the clearance fit (small change) and then beat the frame hole ovaled over 700 miles (big change). same with the upper shackle bolts, should fit the hole exactly, and there is usually a shim on the bottom side, not 1/2 inch. the bolts install from the bottom to the top, with a threaded plate on top. here is a picture of the set I just took off a 54. the shims are on top, the plates are there, and you can see the shoulder on some of the bolts. Attached Images __________________ the mass of men live lives of quiet desperation if there is a problem, I can have it. new project WAYNE http://67-72chevytrucks.com/vboard/s...d.php?t=844393

02-17-2020, 09:16 AM	#4
MARTINSR Registered User Join Date: Dec 2000 Location: Boise, Idaho Posts: 6,001	Re: Cab too low at the rear, any ideas? Thanks guys, I thought there was a threaded plate "nut" at the top! I don't have it so large washers and regular nuts is going to be ok there. I could make that plate easy enough. Well sort of easy enough, I don't have a lot of my tools like I did at my old house, no vice, I need to get one. I am thinking it is a little of everything, reproduction bushings too, if everything gives a bit, whamo, there is a bunch of difference. Brian __________________ 1948 Chevy pickup Chopped, Sectioned, 1953 Corvette 235 powered. Once was even 401 Buick mid engined with the carburetor right between the seats! Bought with paper route money in 1973 when I was 15. "Fan of most anything that moves human beings"

02-17-2020, 06:35 PM	#5
mr48chev Registered User Join Date: Jul 2007 Location: Toppenish, WA Posts: 15,265	Re: Cab too low at the rear, any ideas? I've got the assembly manual pages here https://s173.photobucket.com/user/mr...?sort=2&page=1 The shackle setup here. I'm not sure how close that will come on yours though. It may be that shimmed up to sit level the way you want it counts more than exact measurement. __________________ Founding member of the too many projects, too little time and money club. My ongoing truck projects: 48 Chev 3100 that will run a 292 Six. 71 GMC 2500 that is getting a Cad 500 transplant. 77 C 30 dualie, 454, 4 speed with a 10 foot flatbed and hoist. It does the heavy work and hauls the projects around.

02-17-2020, 11:52 PM	#6
MARTINSR Registered User Join Date: Dec 2000 Location: Boise, Idaho Posts: 6,001	Re: Cab too low at the rear, any ideas? I am making shims, I am thinking a little enlarging of the holes a little bending of the floor, a little this a little that, add up. Brian __________________ 1948 Chevy pickup Chopped, Sectioned, 1953 Corvette 235 powered. Once was even 401 Buick mid engined with the carburetor right between the seats! Bought with paper route money in 1973 when I was 15. "Fan of most anything that moves human beings"

02-18-2020, 02:32 AM	#7
mr48chev Registered User Join Date: Jul 2007 Location: Toppenish, WA Posts: 15,265	Re: Cab too low at the rear, any ideas? You might want to make your shims long enough to spread the weight out. I wasn't sure if that was a 48 cab or a replacement but that part looks to be later edition like this 53 floor on one of my cabs. This shot marked for someone with a 47/48 truck showing that the piece went all the way across. That is the cab that had the top cut off that is stuck under the shed that fell down. __________________ Founding member of the too many projects, too little time and money club. My ongoing truck projects: 48 Chev 3100 that will run a 292 Six. 71 GMC 2500 that is getting a Cad 500 transplant. 77 C 30 dualie, 454, 4 speed with a 10 foot flatbed and hoist. It does the heavy work and hauls the projects around.

02-18-2020, 09:44 AM	#8
MARTINSR Registered User Join Date: Dec 2000 Location: Boise, Idaho Posts: 6,001	Re: Cab too low at the rear, any ideas? It's a 52ish cab I believe. Brian __________________ 1948 Chevy pickup Chopped, Sectioned, 1953 Corvette 235 powered. Once was even 401 Buick mid engined with the carburetor right between the seats! Bought with paper route money in 1973 when I was 15. "Fan of most anything that moves human beings"

02-19-2020, 01:16 AM	#9
mr48chev Registered User Join Date: Jul 2007 Location: Toppenish, WA Posts: 15,265	Re: Cab too low at the rear, any ideas? Should be set up right for the shackles then. I was looking today figuring what it was going to take to dig that blue cab out of where it is and after I get the tin roof out of the way it will be chain saw time. __________________ Founding member of the too many projects, too little time and money club. My ongoing truck projects: 48 Chev 3100 that will run a 292 Six. 71 GMC 2500 that is getting a Cad 500 transplant. 77 C 30 dualie, 454, 4 speed with a 10 foot flatbed and hoist. It does the heavy work and hauls the projects around.

02-19-2020, 01:28 AM	#10
vintovka Registered User Join Date: Aug 2016 Location: Hunkered Down Posts: 1,772	Re: Cab too low at the rear, any ideas? Got tired of the old, worn out, original cab mounts. Tossed them and went with 1"x 4"x 5" shims made from Choice Deck synthetic decking leftover from my bed and last deck project. Added 1/2" bolts with 2" HD washer to bolt cab directly to frame. No felt difference from the old mounts plus the choice deck seems to have some cushion/vibration damping qualities. Seems it does not "sway" when turning ether. No signs of stress on cab or mounts either. Squared the cab to the frame this way and no more "butt sag" or touching the running board aprons. __________________ 1954 USAF 3100 http://67-72chevytrucks.com/vboard/s...d.php?t=714917

02-24-2020, 08:32 PM	#11
dsraven Registered User Join Date: Nov 2010 Location: calgary alberta Posts: 7,823	Re: Cab too low at the rear, any ideas? If you are gonna swap the mounts out you might consider energy suspension generic mounts, fab some frame mounts and cab mounts, with extra support, and go with that. Easy enough for an old hotrodder like yourself to figure out. Otherwise, support the sheet metal and them shim as required. On a level floor with a good level on the cab. Trial and error man, you know.



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