Let's talk Tranny!To weld or not to weld?: Grassroots Motorsports forum: Grassroots Motorsports Magazine

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Oct. 13, 2009 4:12 p.m. 20Ver New Reader

First welcome to me. While I'm not new I disappeared for a while and my old login seems to have vanished as well.

I'm off and running on my 2010 car and am excited to make this work. I'll be putting together a full project post on here at some point in the near future.

Car will be a VW mk2 GTI with a Corrado VR6 swap. But I'm working on my mental prep list now. I am trying to decide on whether or not I want to weld the diff. I've rebuilt plenty of O2O's (VW's rod shift transmission), but I have never rebuilt an O2A (VW's cable shift transmission). I'm not really worried about it, just something new to learn.

But my question is: Tranny shifts fine now so it does not need a rebuild for the challenge as far a I know. However it of course has an open diff. Now I can pour in some weld and make it solid, but is it worth it?

Future of the Car:
It will be a dedicated play car, it will see autocrosses, drag racing and some track days. I have truck and trailer, but I see myself wanting to drive it for fun on the odd Friday night and to local events. I've only ever driven our old AWD rally car with welded diffs and one 4 banger road race VW with a welded diff. Ever other fun VW I have had has had an LSD in it.

You guy's have a lot more experience on me, so what do you think? One other thought is weld it up, challenge it and if I hate it spend the money on a diff after the challenge. Sure it means another tear down, but that's not the end of the world. Plus then I could do a proper rebuild the second time around.
Oct. 13, 2009 4:34 p.m. ignorant SuperDork

Why would you weld a Tranny? Wouldn't it just ruin the "SURPRISE"...
Oct. 13, 2009 4:51 p.m. fiat22turbo SuperDork

Remember how that welded car "worked" at low speeds on tarmac? Yeah, basically they tend to try to rip your thumbs off if you touch the gas and forget pushing them around the paddock.
Oct. 13, 2009 5:25 p.m. 20Ver New Reader

fiat22turbo wrote:

Remember how that welded car "worked" at low speeds on tarmac? Yeah, basically they tend to try to rip your thumbs off if you touch the gas and forget pushing them around the paddock.

you mean a 323 GTX hoping backing out of a parking lot spot causes some drivetrain binding? Yeah it sucked, until it got on the gravel, the mud or the snow. Of course it was also odd that as we got faster we also broken more and more tranny parts.

I'll be honest I just don't have enough Autocross experience to know for sure.

What sucks is the O2O transmission are lighter and also can be put together with a cheap shim kit that gives them a tiny bit of diff (opens at 80 foot pounds I think)
Oct. 14, 2009 12:01 p.m. fiat22turbo SuperDork

Okay, let me say it this way:

http://grassrootsmotorsports.com/articles/whats-diff/

There was a better article written on differentials for a FWD car that isn't online. Tim? Think you could find that article and post it online?

Either run a limited slip (even if it is a Phantom Grip, etc) or don't. Welded diffs and sticky surfaces do not work well on a FWD car (they don't work on a RWD car either, but you can adjust things enough to make it passable for road racing)
Oct. 14, 2009 1:05 p.m. poopshovel SuperDork

Uninformed conjectural opinion:

For the challenge, run a phantom slip, unless you're strictly interested in laying down wicked drag times. The "ripping your thumbs off" image is what comes to my mind as well...at least until all that beautiful bubble-gummy welded goodness comes apart.
Oct. 14, 2009 1:17 p.m. andrave HalfDork

http://grassrootsmotorsports.com/forum/grm/weldedsolid-front-wheel-drive-diff-bene...

consensus:

dont do it.