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Old 10-03-2019, 09:54 AM   #1
regan56
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700r4 Trans and stock crossmember

I have a 700r4 trans for my 56..will the stock crossmember work? I have a feeling no since the transmissions are completely different. OE was a column shift.
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Old 10-03-2019, 11:38 AM   #2
59chev
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Re: 700r4 Trans and stock crossmember

The stock 3 speed had no support, it was just held on by the bolts on the bellhousing. The stock crossmember supported the bellhousing, so no it won't work for your 700r4.

If you are going to be running an underfloor master cylinder make sure you get that mocked up first because you will need to work around it for the transmission crossmember.

Alot of guys have used a universal crossmember like this one. Check out KMS Tools, Scotts Supertrucks in Penhold or Bills Truck Shop for Canadian retailers

https://www.kmstools.com/cpp-1947-59...smember-112541

https://www.kmstools.com/counterpart...ed-or-pg-14971

Another place to look if you want to fab something up is Welder Series in Ontario. I've used their transmission crossmember and 4 link in my 59.

Good luck on your project!
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Old 10-03-2019, 12:24 PM   #3
dsraven
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Re: 700r4 Trans and stock crossmember

you could simply fab something up pretty easily. it might be cheaper to buy a universl fit one though. one thing to remember is that the original cross member went right behind the engine and the stock bellhousing sat on it. that cross member also held the frame rails together so with it gone you may experience some issues with the cab mounts moving due to frame flex. a good stout cross member behind the trans would be a good idea. one that does a good job of holding the frame rails at the top and bottom. I know some guys will just bolt a cross member to the bottom rail of the frame but a connection to the top of the frame would also be good to keep things from moving too much. remember the old square body trucks with the trans cross member that bolted to the lower rail and then had a bracket to the top rail? something like that would work. remember to do like 59 chev advises and mock up some other stuff that may get in the way or not have room for later. also remember to leave room for the exhaust, shifter (if floor shifter or cable shifter, you don't wanna burn the cable on the exhaust), leave room for fuel and brake lines routing etc.
square tube is a good thing to use for a cross member simply because it is square and easier to make brackets fit against it or cut and get angles to fit without a lot of tubing notching etc. it is harder to bend though so cut and weld would work there if you don't have a square tube bender. round tube is also good and can be bent at the local muffler shop. some guys will use a flat flange that bolts to the web of the frame rail and then comes down and across to the other side. these are probably stronger than the ones that just bolt up to the lower rail because they keep the web of the frame captured better

check post 12 of this thread to see what I mean about connecting the upper and lower frame rails with brackets. this is a 4x4 arrangement so there are a couple of cross members close together. the one shows the stock squarebody arrangement I was talking about further back in here.

http://67-72chevytrucks.com/vboard/s...d.php?t=236086

another idea for fabbing your own and connecting the upper and lower rails

http://cfm.industries/gm-squarebody-...e-crossmember/

https://westernchassisinc.com/catalo...per-p-556.html

another thread on here dedicated to transmission cross members

http://67-72chevytrucks.com/vboard/s...d.php?t=486119
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Old 10-03-2019, 12:37 PM   #4
regan56
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Re: 700r4 Trans and stock crossmember

good stuff men! keep it coming!
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Old 10-03-2019, 12:39 PM   #5
dsraven
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Re: 700r4 Trans and stock crossmember

you will likely be fabbing up some new engine mounts if changing the trans I would assume you are changing the engine configuration as well? some of these trucks came with a SBC which had front engine mounts so if you are thinking of installing an auto then the original trans cross member will have to go or be cut/reconfigured to fit under the auto. thats not a totally bad idea to cut and fab a center section bolt in drop out member so the frame canstill be held in that area. since the stock v8 mounts are front and the stock auto 700r4 trans would be a rear mount that leaves a lot of space between the front and rear mounts. you might think of using the oil pan and trans flywheel cover from a 4x4 truck in the 80's to 90's vintage because these units had a set of struts to reinforce the connection between the engine and trans. they are bolt on. if you have room for that under your engine that would help the tendency for the joint from engine to trans to sag. the bellhousing only withstands so much before cracks etc appear. not sure of your configuration, IFS, solid axle etc. anyway, something to think about.

flywheel cover

http://www.2040-parts.com/700r4-or-t...-4wd-i1920367/

a forum talking about the same thing only a different truck
https://forums.ihpartsamerica.com/showthread.php?t=1274
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Old 10-03-2019, 01:42 PM   #6
regan56
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Re: 700r4 Trans and stock crossmember

Quote:
Originally Posted by dsraven View Post
you will likely be fabbing up some new engine mounts if changing the trans I would assume you are changing the engine configuration as well? some of these trucks came with a SBC which had front engine mounts so if you are thinking of installing an auto then the original trans cross member will have to go or be cut/reconfigured to fit under the auto. thats not a totally bad idea to cut and fab a center section bolt in drop out member so the frame canstill be held in that area. since the stock v8 mounts are front and the stock auto 700r4 trans would be a rear mount that leaves a lot of space between the front and rear mounts. you might think of using the oil pan and trans flywheel cover from a 4x4 truck in the 80's to 90's vintage because these units had a set of struts to reinforce the connection between the engine and trans. they are bolt on. if you have room for that under your engine that would help the tendency for the joint from engine to trans to sag. the bellhousing only withstands so much before cracks etc appear. not sure of your configuration, IFS, solid axle etc. anyway, something to think about.

flywheel cover

http://www.2040-parts.com/700r4-or-t...-4wd-i1920367/

a forum talking about the same thing only a different truck
https://forums.ihpartsamerica.com/showthread.php?t=1274
indeed.

i do have a 327 and aftermarket V8 engine mounts for the truck already.
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Old 10-03-2019, 02:16 PM   #7
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Re: 700r4 Trans and stock crossmember

Awesome. I have a 327 and a 700r4 mocked up in my 59. I changed out my front suspension for a camaro clip though..and deleted the stock transmission crossmember in the process..
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Old 10-03-2019, 02:46 PM   #8
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Re: 700r4 Trans and stock crossmember

The stock crossmember that the cast iron bellhousing for the stick trans sits on is going to be in the way of any automatic.

I agree 100% mount the master cylinder and work around it.

I'd suggest mocking the setup up and figuring out exactly where the mount on the tai shaft is going to sit in relation to the frame rail height and go from there. There are "universal" tube crossmembers with all kinds of drops in them that make things easy that run around 60 bucks US most of the time but sometimes you can get a serious deal if you have Amazon prime.

Welders series makes some nice fab it up yourself pieces and I have used a fair amount of their stuff. I like their gussets because they are a lot neater and cleaner than what I can make myself and not too spendy most of the time.

Making your own crossmember mostly depends on your personal fab skills and what equipment you have at your disposal. It really isn't fair for the rest of us to assume that one has a welder, cut off saw and the skills to design and fab something that works good and looks good. Cutting a length of channel iron to length and drilling a few holes and bolting it up isn't fabbing even though it gets done and some guys think it is great.
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Old 05-15-2021, 05:56 PM   #9
qbeanie
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Re: 700r4 Trans and stock crossmember

This is an old post but i have the same issue. My 57 is an original automatic transmission truck and the bellhousing crossmember is removable. the previous owner of the truck hung the 700R from the original crossmember by lowering the crossmember and utilizing the lower crossmember mounting holes on the frame rails. I was going to fabricate a new crossmemberr that would allow clearance for the 700R torque converter dust cover along with a rear crossmember to support the transmission. My question is could a i simply fabricate boxing plates utilizing the existing bellhousing crossmember flange bolt pattern on the frame to prevent frame flex and potential cab sag and front spring issues?

Last edited by qbeanie; 05-18-2021 at 03:13 PM.
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Old 05-15-2021, 09:15 PM   #10
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Re: 700r4 Trans and stock crossmember

I'd say you are absolutely on the right track. That will save the bent in the middle can't get the gap between the doors and fenders right thing down the road.
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Old 05-15-2021, 11:07 PM   #11
dsraven
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Re: 700r4 Trans and stock crossmember

How about some channel laid on its flat side against the frame or against a short boxing plate on the inside of the frame, then bent in a U shape to go under the trans and then again to come up the other side. For the bends you could simply cut off the flanges of the channel for that section then bend the remaining central flat part around something of the right diameter, then jig it so it stays in that shape (like lay it on its side and tack it to the workbench) and make some new flanges for the channel from flat sheet to fit around the bend and weld them on. You could do the same U shaped idea with tubing as welI I suppose , with flat flanges welded on for frame mounts, but most guys dont have a pipe bender.
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Old 05-18-2021, 02:33 PM   #12
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Re: 700r4 Trans and stock crossmember

Quote:
Originally Posted by qbeanie View Post
to prevent frame flex and potential cab sag and front spring issues?
i commend you for taking the effort to support the cab and spring hangers, most here did not
orrieg has a stock x-member with automatic, it took a little trimming and finagling
it sounds like your on the right track, the cab will sit on the frame without some support

i did a little different method, same as the high dollar frame builders do
i fabbed up a stout rear x-member and came off that to the cab supports
not sure how this would work with front springs, truk has mustII ifs
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