Engineers and examples: 2 crossmembers needed with 4 speed Atlas or Titan and NP205

[TAC71]

Hey Brian. I actually have 3 mount points on my 203 D 20 setup. One under the standard spot on the ZF and 2 mounts on the back of the D20 . Didn't feel happy with a 203 and D20 hanging off the back of the trans case. All 3 mounts are on a tubular cradle with 5 solid mount points on the frame. The cradle tubes snake around the underside of the trans and T cases.
You know how long I have been running this setup.....ZERO problems.

 

[nvrstuk]

I was actually going to text you today...



Thanks!!

 

[toddz69]

Todd- so you are saying the adapter btw the Atlas and your trans has a mount?

Yes - it's this one:

https://www.advanceadapters.com/products/as-6800--th350-to-atlas-adapter/

Todd Z.

 

[nvrstuk]

Yeah...no adapter plate for my install, I can't afford to put any kind of spacer in to increase the length of my drivetrain, so it's the back of the trans or the back of the 205... or back to both...

I'll do some more figuring... I still like whatever I can do to support the Titan and 205...


Thanks for the link Todd.

 

[TAC71]

You want me to send you a few pics under mine?

 

[nvrstuk]

Much appreciated Gary!

 

[OX1]

What I did on C6/blackbox/205. Never finished rig, can't say on durability or even if "over cross-membered"...........

 

[Yeller]

do you have room to add a tube between the PTO cover and mount on the transmission? and then a mount to that tube under the doubler? That would be my personal choice, and if space is tight make it out of plate to skinny it up more.

 

[OX1]

I think if you do the back of trans X-member, and then only side mount like this.

That is very close to how 205 was mounted from factory. (granted my side mount is much more
restrctive than factory mount, that had two huge thick rubber bushings).

 

[Digger556]

What I did on C6/blackbox/205. Never finished rig, can't say on durability or even if "over cross-membered"...........

No offense intended here, but that is what you don't want to do.

As the frame flexes, it will try twisting the whole drivetrain, like wringing a towel. Something will eventually have to give. Hopefully it will just be a mount and not a tail housing or T-case.

The frame also bows up and down quite a bit under normal driving. With 5 pts of contact, the drivetrain is now part of the frame structure. Since the drivetrain is much stiffer than than frame, it will take most of the bending load until something breaks.

 

[OX1]

No offense intended here, but that is what you don't want to do.

As the frame flexes, it will try twisting the whole drivetrain, like wringing a towel. Something will eventually have to give. Hopefully it will just be a mount and not a tail housing or T-case.

The frame also bows up and down quite a bit under normal driving. With 5 pts of contact, the drivetrain is now part of the frame structure. Since the drivetrain is much stiffer than than frame, it will take most of the bending load until something breaks.

I hear ya, but my buddy on his 89 (460EFI/C6/203/205) on 42's has had this setup exactly like this for 13 years (very hard core crawling use). Probably a little more forgiving in FSB frame being wider, but otherwise no issues. So while I generally agree with your points, I just copied what has already worked.........

 

[nvrstuk]

Look at Ox1's front trans mount.

Use the same bushing in the same plane "centered under the main shaft under the center of the rear 205 shaft by using a plate off the rear output housing (using 5 or more of the mounting bolts to spread load) that allows the same type of bushing used off the rear of the trans mount, preferably at the same height relative to the frame so the torque/twisting load is the same under load.

Unless I can twist tubing into a beautiful pretzel like Gary did, this is the best I can come up with...

Steve- I'm having a tough time visualizing what you suggested... (maybe I need another cup of coffee this am).

Is the mount in the pic attached strong enough and/or close enough to the same type of bushing/mount used for the rear of the 4r70w to make the load between the two close enough to not cause carnage?

 

[Yeller]

This is a horrible drawing but it might help. the red is the bridge between the mounts and the yellow is the crossmember

 

[nvrstuk]

With or w/o the upper drivers side 205 mount?

 

[Yeller]

without the upper mount. If space is really tight I'd do just the one on the output like above before I'd add more mounts. the issue is frame flex and a triangle deals with that very well without inducing more bind on parts that are very strong but do not like being bent.

 

[ntsqd]

build a cage supporting both tranny and transfer, effectively making them one unit, then devise a mount from that to the frame. Walla. By cage I mean no poly bushings, use solid metal to metal on the cage, then poly or rubber from the cage to the frame. Walla again.

This is exactly what a friend did when he put a Corolla GTS engine/trans in a Samurai. Intermediate drive-shaft was built from 4 companion flanges and 2 U-J's. When he had the trans mounted separately from the Sami's divorced t/c ANY twist, regardless of source, made for really bad vibes. Building structure to mount the t/c to the engine-trans, and THEN mounting that to the frame via a elastometric bushing eliminated 90%+ of the vibes.

Lars, Digger, & Yeller are all saying the same thing that I will say, ONE trans mount. Combined with the two engine mounts you have 3 points. Which defines a plane. Can twist the snot out of the frame in any direction and you can't put any torque on the engine-trans-t/c combo. Add even one more mount and now you can, and when you do you break stuff. If you do, and you don't break stuff then one of those mounts is very compliant. Enough so that I'd wonder what it's really doing.