I ordered my Moser M9 with a TH400 crossmember since I figured it would be the closest fit for my 80E, but here's what I'm looking at:



I think the transmission will go up the 1/2" it needs for the crossmember to snug up to the subframe, but its around 6" forward of the trans mount, as seen in this pic:



The trans mount will definitely need some additional support, but with exhaust and the torque arm also needing to share that space, I can't see a real clear way to make it all look clean.

Basically the torque arm mount needs to stay where its at because I really don't want to cut up my fancy M9 Torque arm... Any ideas?

 

I'm actually really surprised that it seems that noone makes one for a 4l80e swap. After doing a little measuring I don't believe that any of the ones that are currently made will be even close besides maybe a T56 one, I planned on making my own.

Any chance you can do the rest of us considering this swap a favor and get some clear pictures/measurements how much lower than stock/how much below the lowest point/subframe rails the pan ends up? I basically have everything sitting around to do the swap but am considering selling it all off because I'm concerned about loosing too much ground clearance on an already low car that I want to go lower with. (I think it would add useful information to this thread if it ever takes off, but if you don't feel like polluting your thread feel free to PM me or start a new one and I'll delete this part of my post- thanks)

 

Hmm how are you planning on routing the exhaust? Does driver bank have to cross over that point for y pipe configuration?

Looks as if you can weld in an extension piece to allow trans to bolt to xmember but it will need to be somewhat triangulated on back side to give it strength. Fish eye a round pipe attach to xmember and then add mount piece and brace it well

 

BMR used to make a swap crossmember but apparently it didn't fit for **** and is no longer available (at least through summit, and can't find it on the bmr site). I'll get some more pics and numbers once I figure it out a little more. Unfortunately my 700r4 is long gone, so I won't have any basis for comparison.


The exhaust will merge in front of the engine, up near the passenger fenderwell

What I'm envisioning now is a driveshaft loop about 12" to the rear of the crossmember, with a couple small diameter tubes running forward from the driveshaft loop structure to the Moser xmember, with a plate in between them for the trans bushing.

Exhaust is still gonna be an issue since its gonna be 4" diameter all the way out the back.

 

lol, my parts car has a 700r4 in it... with a smashed tranny pan and messed up frame rails so I'm not sure I could tell you how low it sits either... my project has a T5 in it now. Any numbers/pictures that would give a good impression about how much ground clearance it will cost would be appreciated. I'm going to be running drop spindles and weight jacks in my project car, and was hoping to go quite low (probably close to as low as my '83 which was probably close to 3" lower than stock), and I'm doubting I can get away with that and a 4L80e...

 

Heres what I did


Id dump that crossmember and build your own. Id also recommend whatever SFCs you use incorporate a trans mount as the stock location is too far forward to be useful with the '80E. The stress of the trans, plus TA both giving it hell is hard on any U shaped crossmember. FWIW, you'll have NO ground clearance with that crossmember. I snaked 3" tubes on either side of the trans to a 4" catback and my clearance was so-so at stock ride height

Also, check your driveline angle. IIRC, the trans jacked up until it hit the trans tunnel still resulted in a tail down 5* incline which wasnt ideal for the DS jouints

 

That crossmember isn't much of a U-shape. I may cut it and weld in a 1/4" plate "hoop" to clear the exhaust, but that torque arm mount has to stay right where it is...

I may replicate the BMR type torque arm mounts where there's a tube running between the SFC's from side to side, about 8" behind the U-joint, and then just run a c-channel forward to the trans crossmember for the trans mount

How did you solve the driveline angle problem?

 

The one aftermarket crossmember was definitely a u shape. Yours even with a pedestle added is still a similar shape when looking at the mounting points. My point is to look into it before calling it done

For the driveline angle, I lowered the engine as much as possible and lived with the remaining angle. The engine failed before I had many miles on the DS. Again, check it before calling it good

 

What do you guys think about using the existing seat rail (which runs across the inside of the car) as a place to brace the rear of the transmission mount "framework" to? Lol, what I'm envisioning isn't so much a crossmember anymore as it is a frame.

I figure I could take some 1/4"x2 flat stock and bend it into a hoop that drops from the top of the tunnel between the TQ arm and driveshaft, and loops up the other side of the driveshaft leaving room for exhaust. From that hoop I could run 2 pieces of 1" tube about 4 or 5 inches apart forward to the torque arm crossmember, and then its just some more flat stock between them for the trans mount.

 

Have you thought of using a 200R4 transmission crossmember from a TTA?
The 700r4 is 23" but the TTA Xmember is setup for 28" and the 4l80(e) is 30 3/8s (bellhousing to trans mount).
This Has the TQ arm mount built in and it would be VERY easy to move the mount position 2 more inches to the rear.
(I just happen to have this one for sale too).


PM me if interested

 

80E crossmember/tunnel brace/driveshaft loop







The top section of the driveshaft loop part will be welded into the transmission tunnel directly below the seat mount crossbar is inside the car. The two places where its tacked together will be drilled for 5/16-18 bolts, 2 per side.

I did lose access to the lowest hole for the torque arm, We'll see if that becomes an issue later on. I have about 3/8" between the bracket and tube, so I could fit a standard nut, cut the bolt to the perfect length, and use loctite if necessary.

 

Finished! I'll have it powdercoated with my housing.




From the front of the car you can see the housing, which is about 1 1/2" from bottoming out on the floor. You can also just barely see the crossmember tubes dropping down slightly in the back. Looks like the lowest point on the car is going to be the trans pan.



Showing the drop from the SFC's, the angle is slightly upward so the gap looks bigger. Its about 1 1/4" below SFC level, which is only about 3/4" below the pinch weld.


1 finger width clearance to torque arm. The arm cannot get high enough to hit the bolts.


Same shot without my hand in the way



Side view showing that the torque arm is lower than the tubes when installed in the lowest position


Overall, I'm pretty happy with the way it came out so far. I'll keep this thread updated on any issues I run into with the crossmember as the rest of the car gets put together, including full 4" exhaust from the turbo back.

 

that looks good you took a th400 mount pre-fabricated added tubes going to back with trans mount and driveshaft loop. i like it. it dosen't look over complicated and looks like it bridges the trans to two mounting locations for better support. compared to the big u-shape

 

That's what I was going for! The only issue I may have with it at this point is the driveshaft loop may not be quite close enough to the u joint for NHRA rules. I won't know for sure though until I get a driveshaft.

 

I like that design better than the U as well. Any chance of a rear support to keep the crossmember from attempting to hinge at the bolts? Its still quite a distance from the chassis

 

Are you talking about the driveshaft loop bolts? I think they will be loaded fairly vertically there and at the front. I can't see the crossmember or the trans tunnel moving laterally or longitudinally enough to get out of alignment enough to try and hinge the bolts.

The torque arm should still apply most of its force against the front bolts since it's much closer to the front than the rear. I've just eliminated the moment arm on the front subframe.

 

Maybe this view will clarify. The rear portion is definitely supported

 

I really like that design. DS loop AND rear crossmember support. Very creative

 

Any way you can provide more information about the parts to produce that mount I will need one soon also...

 

The front portion is a TH400 crossmember that came with my Moser M9. It's like 1 1/4" chromoly tube and some angle. The tubes I ran back are 1" 11ga MS, and the driveshaft loop is 2x 1/4" flat stock, formed in a vice with a torch.

If I were to do it again, the only thing I'd do is have my driveshaft on hand so I could make sure the "driveshaft loop" is close enough to the u-joint to keep the NHRA happy.

 

Looks good. U could have gotten a tunnel mount tq arm and then u wouldn't have to worry about all this lol.

 

Thanks I think? I could have kept my 305 and not have had to worry about a lot of things. Lol

(FYI, its the 80E, not the tq arm that necessitated a little more elaborate design)

 

I removed my 350TPI for a HSR 383 I built and then the car was stolen and gutted. I could have thrown a 383 back in but decided to try a BBF to be different. You want to talk about a lot of worrying and issues lol.

It was a compliment, thats a badass setup. mucho $$ but nice. I would have went with the 80E but didn't like that I needed a controller as well as a block adapter for my 521BBF. I went with the 2004R behind my 521 bc they can handle the power and are non electronic but have a better gear spread than the 700r4… plus it cost a lot less that an 80E.

I was only talking about the tq arm as you would of had a bolt in foundation for the DS, and one less thing to worry bout with the fabbing.

Nice work and carry on!

 

Gotcha, I guess I assumed that was another comment about how, with a compromise, I could have saved a big headache (which I don't feel that any project I've undertaken on this car has been a headache, I've enjoyed building it lol). I'm sure you've gotten plenty of those types of comments with your swap lol.

Trans control won't be an issue since I'll be running a 5.3 anyway, and I scored this trans for $300, so it wasn't terribly expensive either. The Moser torque arm is a nice piece too, and factory style bolt in tunnel mount torque arms would not have worked with the axle housing. Overall cost on the crossmember was much cheaper than a pre-fabbed piece too!