I wanna know, is there anyone out there thats racing their FWD with a welded differential. Also how long do the axles last. This is for road racing and autocross guys. This car will not be drag raced.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ITAcelica &raquo;</TD></TR><TR><TD CLASS="quote"> I wanna know, is there anyone out there thats racing their FWD with a welded differential. Also how long do the axles last. This is for road racing and autocross guys. This car will not be drag raced.</TD></TR></TABLE>

Wouldn't a welded dif give the same or very similar results as a drag spool and cause the wheels to rotate identically while turning? Isn't the the point of having "limited slip" in a non-drag racing enviornment?

 

Probably the most successful fwd welded diff racer is Chris Albin who has a bloody fast ITB Golf and a really good G Prod Golf as well. Although everyone talks about breaking CVs but he claims to get years of service from his axles and not had a specific failure.

He is a very fast driver with a really charging style. There are those who say he is a good enough driver that it overcomes the welded diff issues and those who say the welded diff contributes to his speed. I have watched him at Road Atlanta (really studied him in Turn 5) and he has adapted his style to include some level of hooking inside front wheels on the inside of berms to help rotate the car ala ditch hooking like pro rally guys sometimes do.

I think autocross would require way too tight turning for a welded diff to work but the broader corners of road racing may work for you.

 

One of the few things about which I can speak with authority...

I've roadraced FWD cars with welded difs because back in the ol' days (like the 1990s) we didn't have all of the LSD options available today. They work fine but are a major PITA to drive around in the paddock - particularly backing up where you can get what we called "diff whip," where the wheel gets yanked out of your hands.

In practical terms, when the car gets "up on a plane" with the front tires operating at racing slip angles, there is enough give where the rubber meets the road to make up for loss of differential effect. Even in slow corners (Pacific Raceways 3A/3B is as tight as they come), a welded diff is not the understeering beast that some might think.

They can be twitchy as hell in the wet but if you let them have their head, they come back to you eventually. The greatest thing is that you can drive them anywhere: Want to tighten your line? Steer into the corner and step on the throttle. Want to let it run? Lighten your touch and step on the throttle.

K

EDIT - I'd agree about a welded diff being a bit much for autocrossing...

 

Thanks guys for the info. Now you guys know that I ran a Celica in ITA that weights 2700lb. I seen welded diffs on GTIs and other VWs but never on a Celica. This is my chep way of getting close to an LSD. Again thinks for the info and keep it coming.

 

If the parts availability or the budget for a true LSD is scarce but you have access to a spare tranny in case you don't like it, then I'd think a welded diff would be worth the giving it a try. There is no doubt that an open diff can be slow and cause other issues if you are a dedicated throttle-on racer so giving a welded diff a try might be your best bet. If you have a spare tranny, what else have you got to lose and you certainly are likely to have a lot to gain.

I have driven an ITA RX7 and an ITS 280Z with welded diffs the the front engine/rear drive layout is quite different. The real key that I found was that you had to be really good at rev matching when downshifting as quickly both rear wheels may be going slower than road speed if you get it wrong. This means lockup at least in a stragiht line and a snap spin if you are cornering.

 

I can find a good tranny for only $200. I am going to give this a try, thinks for the info.

 

Kirk and Lee,

What do you have to say about Corner Entry?

You're turning in, with no differential, and you're not "up on the tires" yet.

At that point does it feel pushy? Does it matter?

Does Albin's style include a "big pitch" to vault him quickly "up on the tires"?

I've sometimes wondered about this since my experience with going in hot has resulted in a tendency to push off.

Scott, who hasn't driven a welded or spool....

 

In my experience, a welded diff only seems to make an off-throttle or trail brake entry better, in terms of getting the car to turn in. It also allows you to get back on the throttle - even part throttle - way early, adjusting the line and attitude of the car with throttle, LFB, or steering inputs.

Note here that I am a trailbraker by nature so I might have more slip angle in the front tires sooner than someone who drives a more "classic" line. Either that or I am slow enough that I'm not dangerously near the push-off-at-entry point of the car's envelope. The second is likely.

K

 

Kirk,

Part of my reason for asking is that I've been told by "experts" that up to the point at which you resume pushing down on the throttle, an open diff is superior.

Having been told that Pierre prefers a Quaiffe (which functions as an open diff when off the power) over a cam/clutch style diff, I thought "well, there you go".

But without personal experience, I'm not so sure. And now here you are implicitly advocating a solid diff.

And, there being nothing simpler or lighter than a spool, it's hard not to take notice of the possibility that even with a different mix of pluses and minuses, that a spool might be a reasonable choice.

Well, reasonable up to the instant that you break a cv or axle and get jerked into a wall.

Scott, who would miss his power steering that much more with a spool...

 

Kinda related:

How may spider gears does your Celica diff have? I have heard magic-voodoo that 4 gears make it act more like a LSD, than a normal 2 spider gear open diff would!
A guy I know with a Dodge Omni swapped in a 4 spider gear diff from a Daytona and said it was like night and day...

I am unsure how this works (or if it does!), but surmise that it's because of more resistance to change (friction of 4 gears, as opposed to 2), allowing an extra split second before the inside wheel spins in a turn?

 

unfortunately this:


costs alsmost as much as an OPM LSD. Even so, I'd say the best answer is to try it and see which you prefer.

Sean, who wonders about the power gains from less weight & friction from a spool over a spinning pack of gears & clutches....

 

How is the GCR worded exactly? Does "diffs are open" allow no diff at all? I know people are using welded diffs, just curious what the rules say.

 

that means you are required to have an open Diff

 

I was suggested by local racer to just weld my tranny. He is a good source, wins races and has been racing awhile.(his is a VW golf). He wasn't suggesting it to save me money.

I asked if i didn't like it would it be the same part/parts i would be taking out to install a LSD. He said yes.
Is this correct?
Curious about how much more tire wear i might have? If i am chewing up tires every two races, then its not worth it to me.

thanks

 

I think you have a good point there James. Because iam only doing this to save some money. If i spend $970 for a Kaaz LSD and get 4 or 5 weekends out of my tiers, iam a happy man, but if i weld my diff and only get 2 weekends out of my tier, then ill be very mad because I wont save any money.

 

I'm not necessarily advocating for a spool over a "real" LSD, if costs are similar. In fact, that would be an easy choice for me since as much as I thought a welded diff was a good thing, the VWMS unit that followed it was better. (I think it was a clutch type.)

In terms of value for money, a welded unit is pretty darned OK. I've seen them literally stick welded until they were a glowing blob, then dropped in a bucket of water - only to survive multiple seasons of racing.

On the power steering note, the welded diff was totally OK even at hillclimbs where the speeds are lower and the corners sharper, even with a manual rack and substantial castor in the front end.

K

 

depending on how big your tires are (if they can take the load) you could stick a big fat sway bar up front so it lifts the inside tire when your turning, ala a go-kart.

Just thought I'd throw that in there.