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Removing rear engine crossmember
#1349111 Sat Mar 07 2020 04:58 AM
Joined: Sep 2019
Posts: 150
R
Shop Shark
Is there any danger of the frame "shifting" on my '50 3100 if I temporarily remove the back engine crossmember? It won't allow the space for installing an LT1 with a 4L60E tranny without modifications. Once I have the combo where I want it, I will reinstall it with the necessary modifications completed. I won't remove any other factory crossmembers.

Re: Removing rear engine crossmember
Rocket man #1349114 Sat Mar 07 2020 05:30 AM
Joined: Feb 2004
Posts: 20,351
H
Boltergeist
Just make sure the frame is well supported on jack stands and level when you remove the crossmember, and when reinstalling the modified part. You'll also need to fabricate mounting points for the mid-engine mounts and a crossmember for the transmission tail shaft, so the only purpose for the dropped crossmember at the bellhousing area is to prevent frame flexing at the spring mounts. If you're doing a butcher job on the frame to install independent front suspension, the frame is probably going to get distorted anyway, no matter how many precautions you attempt.
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Re: Removing rear engine crossmember
Hotrod Lincoln #1349138 Sat Mar 07 2020 02:34 PM
Joined: Mar 2004
Posts: 192
F
Shop Shark
Rocketman: removing and then modifying and then reinstalling that crossmember is certainly doable, however, I’ve attached photos of how I addressed that roadblock. I cut out the center of that crossmember and then fabricated a removable tie-plate of 1/8” steel to straddle that opening. Those are 1/2 inch grade 5 bolts (4 on each side) bolted into 1/2” coupler nuts bolted onto the flange at the bottom of that crossmember. That flange is plenty wide to accommodate the bolts. You can then also adjust the position of the tie-plate as needed to get clearance for the transmission oil pan. Good Luck, Dave

Attached Files
110A6F1F-F2E3-453E-8A8F-EC300A342E75.jpeg (179.04 KB, 276 downloads)
58F0A88A-56B6-4CCC-B6E2-B15DA03D4901.jpeg (178.98 KB, 281 downloads)
D138757C-D193-48A1-958F-D324D340340E.jpeg (166.67 KB, 263 downloads)

1948 5-window 3100 Chevy
327 V-8 TBI 700R4 Posi 3.73
"Old Blue"
In the Stovebolt Gallery
More pix on Flickr
Re: Removing rear engine crossmember
Rocket man #1349152 Sat Mar 07 2020 04:56 PM
Joined: Mar 2010
Posts: 9,223
5
Master Gabster
I'm not a mechanical engineer, but that crossmember connector design does not look to have the kind of support required along the lateral plane.
I am envisioning the bolt heads eventually shearing the metal of the stub end of what is left of the crossmember.
Your 1/8" plate steel should be able to withstand the shear forces inherent to this design, but the original crossmember steel is not as durable as plate steel.
There is a lot of support needed in this area because the spring perches are located in that vicinity.
Personally, I am not so sure that your design will provide that support.

Re: Removing rear engine crossmember
Rocket man #1349156 Sat Mar 07 2020 06:01 PM
Joined: Mar 2004
Posts: 192
F
Shop Shark
52Carl: I appreciate your comments, and granted, my modification is a compromise and not as preferable as the original design, but it has held up for the past 5 years and 5000 miles (I baby my truck). Plus, as you can imagine, removing the transmission is fairly easy (I switched out the 400 Turbo I originally installed in favor of a 4L60). If and when my arrangement fails, I guess I’ll consider further modifications. I just wanted to give Rocketman some ideas. What did you do? Regards, Dave


1948 5-window 3100 Chevy
327 V-8 TBI 700R4 Posi 3.73
"Old Blue"
In the Stovebolt Gallery
More pix on Flickr
Re: Removing rear engine crossmember
Rocket man #1349192 Sun Mar 08 2020 12:18 AM
Joined: Feb 2004
Posts: 20,351
H
Boltergeist
I would have put a couple of 45 degree bends in that plate with some gussets added, or made the stiffener out of 1 1/2" square tubing instead of creating all the stress risers with the bolts and spacers. Of course, I'm accustomed to building frames that survive dirt track racing conditions, where the rule of thumb is "Build it three times a strong as you think it needs to be, and don't be too surprised when it breaks"!
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Re: Removing rear engine crossmember
Flatblu4748 #1349215 Sun Mar 08 2020 02:34 AM
Joined: Mar 2010
Posts: 9,223
5
Master Gabster
Originally Posted by Flatblu4748
52Carl: I appreciate your comments, and granted, my modification is a compromise and not as preferable as the original design, but it has held up for the past 5 years and 5000 miles (I baby my truck). Plus, as you can imagine, removing the transmission is fairly easy (I switched out the 400 Turbo I originally installed in favor of a 4L60). If and when my arrangement fails, I guess I’ll consider further modifications. I just wanted to give Rocketman some ideas. What did you do? Regards, Dave

I was searching far and wide for the pics of what I did but could not find them. I am pretty sure that I posted them on this site.
Basically what I did was made my cuts in the same place that you did, but I cut them perpendicular to the ground. I welded plate steel drop plates to crosmember stub ends as well as to the ends of the cut out section of the crossmember.
I then drilled two holes in the drop plates for 1/2" bolts for easy installation and removal of center section.
This ended up giving me a 2" drop to clear the transmission. I can drop the oil pan on the transmission without removing the center section and it looks somewhat more like a stock setup and is very rigid.
As long as you continue to baby your truck and keep an eye on where your bolts go through your plate steel and the crossmember stub ends for failure, you should be alright.
Carl

Re: Removing rear engine crossmember
Rocket man #1349255 Sun Mar 08 2020 02:37 PM
Joined: Aug 2018
Posts: 33
1
Wrench Fetcher
I just had a buddy help me out with this. Added (4) 3/8" steel plates with heavy gauge hardware. Allows to slide the engine / trans in easy and simply bolt it back in. Pic attached.

Attached Files
rear bracket mod.jpg (245.07 KB, 164 downloads)

Mike

1952 -3100 with '54 235 Iowa farm truck "Cecil"
Re: Removing rear engine crossmember
1952Cecil #1349262 Sun Mar 08 2020 04:47 PM
Joined: Mar 2004
Posts: 192
F
Shop Shark
52Carl: I was able to find your picture that you referenced in your above explanation. I wanted the other Bolters to appreciate your effort....”a picture is worth a thousand words”. Carl, like you, “I’m not an engineer”, either, and everybody’s got an opinion....I’ll just leave it at that...

Attached Files

1948 5-window 3100 Chevy
327 V-8 TBI 700R4 Posi 3.73
"Old Blue"
In the Stovebolt Gallery
More pix on Flickr
Re: Removing rear engine crossmember
Rocket man #1349277 Sun Mar 08 2020 08:22 PM
Joined: May 2015
Posts: 2,367
K
Housekeeping (Moderator) Making a Stovebolt Bed & Paint and Body Shop Forums
I am a mechanical engineer, for what that's worth. wink
I like Mike's (1952Cecil) solution. Nice and stiff. Although it's not dropped that much.
Carl's has a couple of hinge points that would work better if stiffened up a bit. A couple of gussets from the frame side of the plate up to the original crossmember would help immensely.

Last edited by klhansen; Sun Mar 08 2020 08:23 PM.

Kevin
First car '29 Ford Special Coupe
#2 - '29 Ford pickup restored from the ground up.
Newest Project - 51 Chevy 3100 work truck. Photos [flickr.com]
Busting rust since the mid-60's
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