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Transmission crossmember ?


DragCat

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I read in another thread that with increasing HP (i'm dropping in a bigger crate) that the crossmember should also be upgraded to a chevelle part. Is the suggestion just a regular Chevelle crossmember or something a little more beefy like this? 

https://www.ss396.com/mm5/merchant.mvc?Session_ID=75881b1ab9bf1b5f88375433ed613c5f&&Screen=PRODB&Product_Code=FCM-RCAE&Category_Code=chevelle-crossmember

 

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Ok, depends on how you want to go. The reason for replacing the factory Monte Carlo crossmember is due to the rubber isolators at the ends of it. Through time they tend to rot out the crossmember there. With a high horsepower car it usually pulls the crossmember out of the rubber and feels like a broken motor mount when accelerating. 

The reason for the Chevelle crossmember being used is that it used to be readily available and the only thing that fit and bolted directly to the frame. No aftermarket crossmembers back then. Lolol

The one you have pictured is a great piece. I have one in my 70 SS. It will take whatever you throw at it horsepower wise. It is a heavy piece tho if you are looking for weight savings. 

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The stock (reproduced) Chevelle ones look a lot straighter than the MC ones, at least in the exhaust pipe area, unless I'm looking at them wrong. Have you seen that in your experience Tom?

https://www.opgi.com/chassis-suspension/bushings-mounts/1968-72-transmission-crossmember/crossmember-transmission-1968-72-chevelle-ch28177.html

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4 hours ago, MC1of80 said:

Ok, depends on how you want to go. The reason for replacing the factory Monte Carlo crossmember is due to the rubber isolators at the ends of it. Through time they tend to rot out the crossmember there. With a high horsepower car it usually pulls the crossmember out of the rubber and feels like a broken motor mount when accelerating. 

The reason for the Chevelle crossmember being used is that it used to be readily available and the only thing that fit and bolted directly to the frame. No aftermarket crossmembers back then. Lolol

The one you have pictured is a great piece. I have one in my 70 SS. It will take whatever you throw at it horsepower wise. It is a heavy piece tho if you are looking for weight savings. 

Thanks Tom, I don't plan on running any NHRA Stock Eliminator classes so i'm not really worried about the weight lol. Is that just a bolt in or are there some mod's that need to be addressed?  I'm assuming the part the Joe linked would be satisfactory, just a bolt in replacement without changing out the rubber insulators? 

As with any build i'm learning a lot and questioning more lol. I plan on having fun with mine, and yes pushing it hard down the track so I want to do it right the first time. The great thing about this forum is the amount of info available in all formats, on the down side of course the I wasn't expecting I needed one of tho$e lol. But i expected the unknowns and its just part of the deal. 

On a side note i'm jealous of your black carb fuel line on the SBC to BBC 489 post lol. I went with the black from the fuel pump but couldn't find any in black for my carb that didn't have negative or complaints about leaking fuel. I went with the blue/red, guess only i'll know once the air cleaner is on.

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Hey Mark. Using the Chevelle crossmember deletes the Monte Carlos rubber mounts. It bolts directly to the crossmember. 

The G force crossmember bolts directly to the frame also. I did not have to modify it in any way. Bolted right in and gives you great exhaust clearance. You can tuck your exhaust up close to the floor if you like.

Thank you for the compliment! The black carb fuel line/log took awhile to find. I believe I bought it from summit. 

IMG_0036.JPG

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Thanks Tom, i'll have to mull it over lol. Altho I don't want to spend the extra coin i'm leaning toward the G-Force at the moment. Just looks beefier (if thats a word lol) 

I tried Summit, but there were reviews of leaking and I don't mess around with possible fuel leaking problems. Funny thing with a Holley Carb I went with Edelbrock fuel lines. 

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You could always just weld a couple of tabs on the stock crossmember as I did to get 4 mounting bolts to fasten it solid to the frame. You'll have a lot less drama than I did if you're  keeping the T-400 trans.

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G Force is cool, but it is heavy. Plenty of stock Chevelle crossmembers out there. And I am never a fan of Chinese built repops. I had a customer job split the weld on the tabs where the tranny mount attaches. Car was a 72 L48 Th350 Chevelle. Found him a proper used one off Craigslist for $50 local.

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9 hours ago, jft69z said:

You could always just weld a couple of tabs on the stock crossmember as I did to get 4 mounting bolts to fasten it solid to the frame. You'll have a lot less drama than I did if you're  keeping the T-400 trans.

My plan was to keep the original 400 and i'm taking mine to the transmission guy tomorrow for the rebuild. Of course now I have added my cracked bell housing to my list of issues. Tomorrow will tell. I'm just trying to figure out my options and getting feedback from those in the know, oh yea, I don't weld 🤣

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On 2/14/2020 at 7:36 AM, Andy's Auto said:

G Force is cool, but it is heavy. Plenty of stock Chevelle crossmembers out there. And I am never a fan of Chinese built repops. I had a customer job split the weld on the tabs where the tranny mount attaches. Car was a 72 L48 Th350 Chevelle. Found him a proper used one off Craigslist for $50 local.

So are you saying to search CL or similar instead of going to the suppliers like OPGI and such? I'm rethinking the g-force idea, I don't think I need all that 

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On 2/16/2020 at 6:54 PM, DragCat said:

So are you saying to search CL or similar instead of going to the suppliers like OPGI and such? I'm rethinking the g-force idea, I don't think I need all that 

When it comes to structural metal on any Vietnam War era hot rod, 50 year old Buffalo steel is better than Chineseum any day of the week. 

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1 hour ago, Andy's Auto said:

When it comes to structural metal on any Vietnam War era hot rod, 50 year old Buffalo steel is better than Chineseum any day of the week. 

Bethlehem Steel in Lackawanna, NY. About 30 miles from me :). Lot of good jobs back then when the place was open.

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That will work but it's actually for a 4 speed car. The little extension opposite the trans mount is for the Muncie shifter. 

Also, if it's for a convertible, it will not fit. To short. An El Camino crossmember from 68-72 will fit. 

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6 hours ago, MC1of80 said:

That will work but it's actually for a 4 speed car. The little extension opposite the trans mount is for the Muncie shifter. 

Also, if it's for a convertible, it will not fit. To short. An El Camino crossmember from 68-72 will fit. 

Just to make sure, if I run across a Chevelle or ElCamino as you mentioned, does it have to be out of a 454 car, or can it be from any engine option that was available? 

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  • 4 weeks later...
On 2/13/2020 at 12:48 PM, MC1of80 said:

Ok, depends on how you want to go. The reason for replacing the factory Monte Carlo crossmember is due to the rubber isolators at the ends of it. Through time they tend to rot out the crossmember there. With a high horsepower car it usually pulls the crossmember out of the rubber and feels like a broken motor mount when accelerating. 

The reason for the Chevelle crossmember being used is that it used to be readily available and the only thing that fit and bolted directly to the frame. No aftermarket crossmembers back then. Lolol

The one you have pictured is a great piece. I have one in my 70 SS. It will take whatever you throw at it horsepower wise. It is a heavy piece tho if you are looking for weight savings. 

 

Tom, did you have to do any modifications for the bolt holes to line up on the g force? I'm just asking because of some of the reviews. Someone mentioned it was only 10#'s  heavier than a 69 chevelle original so I can deal with that.

Ive exhausted my local chevelle contacts looking for an original 70 chevelle crossmember so I have to make a decision Monday. I'll measure the bolt distance tomorrow just to make sure I get the right one. 

The one from OPGI Joe listed isn't in stock until maybe May? And doesn't give specifics on trans fitting like the ss396 one below (which specifies not with a TH400)

I know its a couple of bucks more lol, but from what ive spent already whats a couple more bucks now 🤣 And NO free shipping 

https://www.ss396.com/chevelle/FCM-88N.html?search_query_insert=Y&search_query=transmission crossm&search_results=6&conversion_insert=Y&conversion_product_id=5691&cartype=chevelle&year=1970

 

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55 minutes ago, DragCat said:

The one from OPGI Joe listed isn't in stock until maybe May? And doesn't give specifics on trans fitting like the ss396 one below (which specifies not with a TH400)

Hey Mark,

I just listed that one for comparison purposes, not an endorsement of OPGI's part. It just looked a lot 'flatter' than our original ones that have a very pronounced hump where the exhaust pipes cross under.

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13 minutes ago, jft69z said:

Hey Mark,

I just listed that one for comparison purposes, not an endorsement of OPGI's part. It just looked a lot 'flatter' than our original ones that have a very pronounced hump where the exhaust pipes cross under.

No problem Joe, I was using that as a comparison too for fitment. 

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The ground up one will fit and work. The reason o believe they say it's not for a 400 is it has 2 bolt holes for the mount to attach. I believe the factory 400 mount was a single stud.

Just use a 2 bolt trans mount if you don't have one already or a Polly mount. It usually has 3 bolt holes in it.

The G force  crossmember, if I remember correctly, needed 2 bolt holes to be enlarged slightly.

Hope this helps. 

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12 hours ago, MC1of80 said:

The ground up one will fit and work. The reason o believe they say it's not for a 400 is it has 2 bolt holes for the mount to attach. I believe the factory 400 mount was a single stud.

Just use a 2 bolt trans mount if you don't have one already or a Polly mount. It usually has 3 bolt holes in it.

The G force  crossmember, if I remember correctly, needed 2 bolt holes to be enlarged slightly.

Hope this helps. 

Thanks Tom, thats what I had read about the bolt holes having to be enlarged. 

I had considered upgrading the engine and trans mounts to poly so I have those in hand, and yes the trans poly mount has 3 holes.

Now that you say the ground up X-member will work i'm going to have to make a decision (laughing) but i'm back to leaning towards the G Force at the moment. Summit has a similar piece but Its about the same price so I will probably go with the name brand. 

Appreciate everyones help and input. 

 

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