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LTX and LSXPutting LT1s, LS1s, and their variants into Third Gens is becoming more popular. This board is for those who are doing and have done the swaps so they can discuss all of their technical aspects including repairs, swap info, and performance upgrades.
This is a guide to transmission crossmembers with LS engine swaps into a 3rd gen F-body.
Transmission crossmembers for LS swaps fall into two basic categories: (1) Straight; and (2) Double-hump. And both types might be offered with or without provision for a torque arm mount. Expanded information about torque arms is here,
Most aftermarket trans crossmembers are of the straight variety. The crossmember essentially cuts across the trans tunnel in a straight path between the right and left side chassis mounts. Disadvantage is the exhaust pipes have to be routed under the crossmember causing reduced ground clearance and putting the exhaust at risk of scraping the ground or even being crushed.
The double-hump trans crossmember is shaped to allow the exhaust pipe to be tucked up higher in the trans tunnel. This is much more desirable from an exhaust packaging standpoint, especially since LS engines run the exhaust thru the trans tunnel. But it leaves very little real estate for a remote torque arm mounting location. Very few companies make a double-hump crossmember despite it's obvious advantages.
The engine and trans mounts must be compatible so that the trans lands properly on the crossmember pad. Nearly all manufactures are standardized on the front plane of transmission being in stock location, and this usually makes it possible to mix parts from different vendors. Hooker Blackheart is a known exception with the engine situated further forward in the engine bay. If you plan to use the Hooker engine mounts or trans crossmember then it is recommended to buy the entire Hooker Blackheart system so that engine, headers, and exhaust package nicely together. Some people have mixed parts from other manufactures but results will vary and its best to research before you buy.
Special Note: Alston inner subframe connectors will interfere with any trans crossmember that uses the rear mounting holes on the vehicle subframe. If using inner subframe connectors, then plan on grinding away material from the trans crossmember, and choose a crossmember that still will be strong enough after the surgery.
Products are listed in alphabetical order:
Double Hump Crossmembers
Hawks Motorsports, https://www.hawksmotorsports.com/
Options for T56 or 4L60 transmissions. No torque arm provision. Easy to route large exhaust. Constructed from plate steel and a bit flimsy compared to others but gets the job done.
Hooker Blackheart, https://www.holley.com/
Modular design with options for T56, 4L60, 4L80, TH400, 2004R. The same crossmember fits all the transmission configurations by interchanging plates on the trans pad. Uses factory mounting points and adds a third mounting point for additional support. Very strong construction! Torque arm provision with adjustable height and uses stock length torque arm with clamshell style mount. Made for 2.5" exhaust and can be difficult to run larger exhaust. Non-conventional trans location with engine and trans further forward in the car.
Skulte
This is the original double-hump crossmember and is no longer in production and very rare. No torque arm provision. Easy to run large exhaust. Made from square aluminum bar stock, lightweight and strong. If you find one of these then expect to pay a lot of money.
Straight Crossmembers
BMR, https://www.bmrsuspension.com/
Options for T56, 4L60, TH350, Powerglide, TH400. Each comes either with or without torque arm provision. Versions with torque arm provision uses stock length torque arm with clamshell style mount.
BRP Hotrods, http://www.brphotrods.com/
Options for T56, 4L60. No torque arm provision. I've never seen this so don't have any more information about it.
Spohn, https://www.spohn.net/
Options for TH350, TH400, Powerglide, Tremec TKO, 200-4R, T-10 Muncie, Richmond 6-speed, 4L60, T56. No torque arm provisions.
Looking for a community effort to get this right. I took a first stab at it. Beat it up, correct my mistakes, add things I forgot. I'll update the first post as you guys add info. Just make sure you know what you're talking about if you post up. I get a free pass on mistakes since I went through the effort to start this.
Two things that would be extra helpful:
1. Pictures
2. Exhaust known to play nice with these parts
The hawks cross member works well but on initial install takes a little bit of effort to get in place sometimes. The first swap I did back in 14' it had to be jacked in place to fit properly. Alignment of all the holes works best if all the bolts are put in loose while the trans is held in place. If you can tuck the pipes right you will have plenty of clearance.
Solid info from the manual on compatibility and necessary parts to go with it:
71222005HKR Transmission crossmember
The Hooker 71222005HKR 3rd-gen crossmember has been CAD designed to work in conjunction with the Hooker 71221003HKR engine brackets to provide bolt-in installation of a TH400*, 2004R*, T56, T56 Magnum, 4L60-4L70* or 4L80/4l85* transmission into any 1984-92 GM F-body vehicle. This crossmember can also be installed in a 1982 or 1983 model year F-body by modifying the location of the stock crossmember attachment holes in the vehicle subframe. This key component has been designed to provide a strong, stiff and low-weight transmission mounting foundation while providing dual arch passages for routing exhaust systems and a divorced, adjustable torque arm mounting provision; the lowest position on the bracket approximates the stock torque are mounting position and moving it up from there raises the instant center of the rear suspension to increase the vehicle anti squat characteristics.
Installation of this crossmember requires the use of a Prothane 7-1604 poly mount or one of equivalent geometry.
*Installation of a TH400, 2004R, 4L60-4L70 or 4L80/4l85 transmission requires the use of the following additional bracket/spacer available from Hooker:
TH400 or 2004R- requires the use of a 12650HKR spacer kit
4L60-4L70- requires the use of a 71223003HKR adapter bracket
4L80/4l85- requires the use of a 71223004HKR adapter bracket
Original pictures from Toddoky of the Hooker Motorsports crossmember:
Last edited by 3.1EyeCandy; 02-21-2021 at 08:18 PM.
Reason: formatting
So do we have any data on one that will work with a UMI K-Member and a 4L60E? I've been searching and still haven't found a solution other than custom fabricating my own.
I never would have bought the UMI kit if I had known I'd run into this upfront, but unfortunately its way too late now.
Just to close out my previous question if anyone is even still interested: The stock 700R4 crossmember fits with the UMI K-Members and a 4L60E utilizing a "K" casing. (this is the earlier style one piece bellhousing/case)
Just to close out my previous question if anyone is even still interested: The stock 700R4 crossmember fits with the UMI K-Members and a 4L60E utilizing a "K" casing. (this is the earlier style one piece bellhousing/case)
What is the issue you are having? I have a UMI 2403 K-member with the Hawks trans mount with the 4L60E. I didn't have the time or the tools to do the heavy stuff myself so I paid others to do that but I am doing the finishing work myself. It isn't running yet so I can't comment on drivability but the folks that did the engine and trans install for me did not mention any alignment issues that I recall. Will be swapping out the rear end, torque arm, LCAs and Panhard soon so I will check everything out while I am under the car.
What is the issue you are having? I have a UMI 2403 K-member with the Hawks trans mount with the 4L60E. I didn't have the time or the tools to do the heavy stuff myself so I paid others to do that but I am doing the finishing work myself. It isn't running yet so I can't comment on drivability but the folks that did the engine and trans install for me did not mention any alignment issues that I recall. Will be swapping out the rear end, torque arm, LCAs and Panhard soon so I will check everything out while I am under the car.
No issues now. I couldn't find any answer to whether there would be any fitment issues, but I lucked out in that the stock crossmember worked.
I'm curious though. Is that Hawks member the double-hump piece? if so, I may look at swapping out to that as I'd really like to run a full dual exhaust in the future
No issues now. I couldn't find any answer to whether there would be any fitment issues, but I lucked out in that the stock crossmember worked.
I'm curious though. Is that Hawks member the double-hump piece? if so, I may look at swapping out to that as I'd really like to run a full dual exhaust in the future
If the Holley crossmember and engine mounts are used will I need to use there headers and have a custom driveshaft made also? Or can I use the hawks headers I have and stock length driveshaft? 6.0/4l80e combo
Last edited by Rubbercity_Iroc; 04-24-2021 at 03:56 PM.
I purchased Hawk's crossmember, big exhaust, and bmr trak pak TA (TA off trans to crossmember). LS2 w/4l65e with large aluminum driveshaft..
Fitment was NOT "fit's like a glove." I had to modify the y-pipe and the trans crossmember. Moved the attachment at frame rail to horizontal with collars welded to frame rail and bolts through those.
The problem is the passenger side - both at the trans crossmember and at the header clamp-frame rail.
Clamps are the lowest thing Tucked up Horizontal attachment to the pass side frame rail Inside pass side attachment very tight w/driveshaft You can see that the header clamps are the lowest point
I purchased Hawk's crossmember, big exhaust, and bmr trak pak TA (TA off trans to crossmember). LS2 w/4l65e with large aluminum driveshaft..
Fitment was NOT "fit's like a glove." I had to modify the y-pipe and the trans crossmember. Moved the attachment at frame rail to horizontal with collars welded to frame rail and bolts through those.
The problem is the passenger side - both at the trans crossmember and at the header clamp-frame rail.
Clamps are the lowest thing Tucked up Horizontal attachment to the pass side frame rail Inside pass side attachment very tight w/driveshaft You can see that the header clamps are the lowest point
I just found a company named s&w performance. There subframe connectors torque arm and drive shaft loop is nice.
If I buy the Hawks T56 crossmember for a 3rd gen, do I need the mounting hardware (bolts I guess?) or will the ones from the 3rd gen mounting bracket work?
02-20-2021, 10:44 PM
