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GForce Trans Crossmember

8K views 20 replies 13 participants last post by  BillyGman 
#1 ·
Nice to be back. I haven't posted in a good long while. My 1971 Chevelle build has been a struggle for many reasons, mostly paint and body reasons.



As I move forward with finishing the build this year, I have encountered a reason to make an inquiry here in my favorite forum. Does anyone have experience using either a tubular style trans crossmember, or a GForce brand crossmember? Likes and dislikes?



I have a TH400 behind my Mark Jones 496, and I have a Gear Vendors Overdrive. I also purchased from Don and Dan Lemons, their tubular, chrome moly trans crossmember. I need clearance for 3" exhaust. Recently I noticed that if I pull up and down on the transmount, while the overdrive unit is not installed, that tubular crossmember bounces up and down a fair amount. It moves enough that if you were looking down at my engine in the engine bay, you would see everything moving up and down. This movement seemed very odd to me as I know the factory crossmember doesn't move at all. I don't think a crossmember should be capable of moving around this much. All Dan said when I called him was they have sold a lot of these and he's never had anyone say they've had a problem.



This lead me to find the GForce crossmember that they advertise as having one specifically designed for a TH400 with a GV. I am very much considering swapping the Lemons crossmember with the GForce, even though I know the GForce will add some weight to the car.
 
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#2 ·
Modify your existing xmember.
I have a Gforce and it's very nice.....but weighs a ton and it's not cheap!
I should have just used my th400 xmember, cut it and welded in steel to reconnect it.
MUCH lighter and MUCH cheaper.
My .02
Oh yeah, I had to use a 1/4" spacer under the trans mount to keep the distributor off the fire wall.
This is with the TALLER polly mount too!
Exhaust notches worked good too, but now the twins go out the side! ;):thumbsup:
 

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#3 ·
I purchased a BRP Hot Rods swap kit off craigslist, had a tubular style trans mount. I've had to weld an exhaust clamp to it because there was no location for the parking brake hook, it's pushed the exhaust down in sight, and I've had to add spacers between it and the frame to get even a barely working angle for the u-joints.

As Chris mentioned above, I'd modify the stock crossmember before I went with another aftermarket setup.
 
#4 ·
I installed a GForce crossmember in my ‘72 to hold up my 2004r.

I had been using the stock crossmember slid backwards, but it was difficult to install/remove and I wanted clearance for my exhaust, and it held the back of the trans up too high.

I like the fitment of the GForce one, gives me lots of room and is easy to install and fit nicely.

It is heavier than the stock one - but it’s pretty beefy so I’m not surprised.
 
#5 ·
I had a tubular one made. Its like the Lemons one, didnt know they made one at the time. Mine moves some, its no big deal. Hundreds of 1/4 mile passes. I wouldn’t worry about it.
 
#9 ·
Thanks for the comments guys. I did speak to Dave Carpenter at GForce today. He said it could also be the frame rails causing my current crossmember to appear as though it is moving. He also said the suspension should absorb any up and down movement and track passes shouldn't be an issue either. He basically talked me into keeping the Lemons crossmember, which is much lighter than the 35lb GForce piece.
 
#10 ·
I have the Lemons tubular crossmember. It is pretty light weight. I haven't noticed and abnormal movement but I haven't done the "grab and shake hard" test. I've driven the car pretty hard and it's behind a well powered big block, so if it was flexing, it hasn't caused a problem.

It nicely clears the exhaust. They come naked, I had it powdercoated.
 

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#11 ·
I used the G-Force in my 69 F Body build with a 540/4L80E combo. It's very beefy (very heavy though) but still flexes a bit with the weight of the engine trans combo. On this particular cross member the passenger side exhaust clearance area is less then desirable; they could have easily added an inch or two of clearance on the trans mount side. If they had, it would have made exhaust routing much simpler. I contemplated sending it back or modifying it (cut/weld) but decided to make it work as is. Granted I'm using 3 & 1/2 inch pipe and to be fair 2 & 1/2 or even 3" would have been okay.

Would I use it again? Not in that application but other applications I've seen have more exhaust clearance so likely would consider it for a different car.
 
#12 · (Edited)
Sounds like the OP has already made his decision, and that's fine, but for others who will read this thread, I went with the G-Force piece despite the massive 34 LB weight. I don't notice any movement but since I had already modified my frame rails to avoid frame flexing anyway, I had to modify the G-Force cross member in order to be able to shorten it a little bit, so I could mount it onto my modified frame rails. I wanted the extra exhaust muffler pipe clearence that the G-Force piece is great for, since I have a 3.5" diameter exhaust. I don't have any pics with the 3.5" diameter muffler pipes installed, but here are some with the G-Force cross member and just the headers, (3.5" diameter collectors).....
 

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#15 · (Edited)
Yep, those are exactly my thoughts too.

Billy, looks like you had to "build up" the trans mount also!
Good to know I wasn't the only one.
Yes, Chris. I first put it all together without building it up. But not only did I have a good 3" between the front U-joint with one of the ears clocked in the 12 O'clock position, and the trans floor tunnel, but when I measured the angle of the front U-joint with the angle finder, I noticed it was pointing downward a few degrees. So as you know, in order to get the trans slip-yoke pointing right at the the rear end pinion yoke, I used a small stack of washers placed underneath the two trans mount bolt holes. The added benefit, (just as you also know) was that it left my engine tilted rearward towards the firewall a little bit less than it had previously been, which in turn gave me more room between the distributor cap and the firewall, as well as my header collectors NOT facing downward and hanging too low to the ground like they had previously been.

So I gained three benefits from a small stack of washers on each of the two trans mounting bolts. And if I remember right, it still left me with 1.5" of clearence between the front U-joint and slip yoke, and the floor tunnel. I sure wish everything in this hobby was that easy to correct. :D

You won't get anymore muffler pipe clearence than you will with the G-Force crossmember. Summit Racing also has their own version which looks to be an exact copy of the G-Force piece. I bet you could even run 4" diameter muffler pipes with the G-Force piece and still not have any clearence problems. And the last thing you want from a trans crossmember is to have the muffler pipes dinging up against them while the engine is idling when your car has a cam with lotsa overlap. A dinging noise like that can drive you nuts. I have my wife to do that already all by herself. So I don't need a car doing that too. ;)
 
#16 ·
This is what I found when I used the th350 mount on the xmember!
Tilted engine WAY TOO LOW towards the firewall!
That th350 mount is 5/8" lower then the poly mount in your picture and the poly mount was still too low!.

See anything wrong with my rotor? :D
 

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#20 ·
I've seen a lot of this with some Chevy into older Ford F series truck engine conversionss, too low a rear trans mount, too high a front mount set. Happens a lot more when a coil in cap large HEI is used. Too bad the conversion kit people just won't listen to this.

When I want to lock the engine down in the chassis, I use either a steel, or poly mount on the driver side engine position only, as this is the side the engine torques up on (no worries on the engine torque on the pass side, it is downward). I use stock rubber mounts on the trans and pass side mounts, as the frame twists and distorts, and I do not want that distortion to harm the engine as the whole mess torques its way to oblivion.

If I need more on the driver side, I add a chain, or solid steel bar between frame and engine.


Also, very important if you use an MSD cap on any distributor. Those caps will fit MSD and stock distributor bodies, but pay particular attention when you install them, they do not simply slide onto the body like a stock cap, they have a very slight interference fit, make sure the cap mounts correctly all the way around it ,and not cocked off the body.
 
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