Differentials- Welded vs. Open vs. LSD

[Jiveslug]

Hey again everyone. Well, work is still progressing on the Corolla and we are getting ready to start with the heavy mechanical work. The interior is about 90% stripped, just have to lose the insulation on the floor boards and pull some of the interior wiring. Anyway, that being said, Im continuing my search for a differential. For this particular car, limited-slip can be hard to come by and rather expensive. Thus, Im considering welding the one I have. The question is, how will this affect my handling? The car is RWD, so Im assuming that welding the diff will make it a bit tail-happy in turns, especially tight ones. The car is also a live axle, so Im not sure if that makes a huge difference vs. independent suspension with a welded diff. Basically, barring my shelling out the big $$ for the LSD, would the welded diff be a better choice than leaving it open? Thanks!!

Ryan

[Greg Amy]

Start here, Ryan:

http://itforum.improvedtouring.com/forums/...wtopic=2968&hl=
http://itforum.improvedtouring.com/forums/...wtopic=3201&hl=
http://itforum.improvedtouring.com/forums/...owtopic=214&hl=
http://itforum.improvedtouring.com/forums/...wtopic=2732&hl=

[MMiskoe]

In a nutshell, a welded diff makes it hard to get a turn initiated. You can pretty much forget about trail braking into a turn as you usually need a bit of throttle to get the thing to start turning. Then its all about using steering input to keep the back behind you. Keeps you busy for sure.

In a lower powered car on big fast turns, the open diff may not matter too much.

[cherokee]

Welded also makes it a pain to push around.

[latebrake]

Originally posted by cherokee@Jan 12 2006, 02:32 PM
Welded also makes it a pain to push around.

[snapback]70795[/snapback]

Yeah. Ask a friend if you can push his welded diff around the paddock. If you are strong and young you can ask to help load it on the trailer. this will help you decide. then push the tow truck and see which one was best.

lawrence

[Ron Earp]

Forget pushing these things by themselves. Bloody hell the JH is light but pushing it around with a welded diff is really hard. Drive it on the trailer.

R

[BMW RACER]

Hey, the up-side of the pushing problem is, you don't need a handbrake! Just turn the steering full lock and leave it, even in nuetral. Trust me it won't go anywhere.

[Jiveslug]

Originally posted by BMW RACER@Jan 12 2006, 08:05 PM
Hey, the up-side of the pushing problem is, you don't need a handbrake! Just turn the steering full lock and leave it, even in nuetral. Trust me it won't go anywhere.

[snapback]70804[/snapback]

Hahahaha. Since youre in my region there John, Ill weld it and you can help me push the car around the paddock at California Speedway.

Well, I guess Ill leave it open for now. Its only an ITB car and Ill be spending most of my time at Cal Speedway and Willow Springs to start (that is, before I start my invasion of Laguna Seca).

Thanks for the info guys!

[tom_sprecher]

This goes way back but to quote I skit off of Ceech and Chong's Big Bamboo

"Push da caa? Get yo momma ta push da caa! Hey, Leroy, wanna buy a watch?"

[racer_tim]

Ryan, I used to crew for an ITD Datsun 1200. He ran a welded diff. Abviouslly a 1200 in IT trip doesn't make a lot of HP, but that's the way he liked it.

I run a welded front diff in my VW Rabbit. LSD is the best but the most expensive. Welded is 2nd best and an open is the worst.

Yes, it's a little difficult to make 90 degree turns in the paddock, but I didn't like driving through turns 2, 7, and 10 @ Sears Point, and having the inside wheel "chirpping" as it was looking for "traction"

Yes, I might have a little bit more "friction" with the locker, but I'll trade that in for both drive wheels "pulling" me through the corner anyday.

It also take's a bit of a different driving style. Like others have said, if your not on the gas, your not turning. This is especially true with the FWD. Brake in a straight line, downshift, turn in for the apex, mash the loud pedal, and aim for the exit. Pretty simple, but it does get a little bit of getting used to.

Others have also said that it's hard on the CV's and hubs. As part of normal maintenance on a VW, you change 1/2 shafts and hubs every year, and have only had 1 CV failure on track in 6 years of racing.

I had my VW gearbox rebuilt and "locked" for $600 in 1994. Haven't touched it since.

[eMKay]

What about welding the diff on a car you also plan to autocross? Would it just destroy CV joints and halfshafts that much quicker?

[Bildon]

What about welding the diff on a car you also plan to autocross? Would it just destroy CV joints and halfshafts that much quicker?
[/b]

Yes, it would be brutal on a FWD cone chaser...

And it's not going to make turn in very easy. For AX you probably want a Torsen (Peloquin or Quaife). However for Road Racing you want a clutch diff.

[racer_tim]

Actually, if you look at the Solo II rules, locked diff's are illegal.

At least they were a couple of years ago.

[billf]

Just a few cents worth...

Any solution is better than an open diff when racing a car with a solid rear axle.

Live axles respond well to welding, relative to their handling. The "lightening" of the inside wheel by leverage from the outside wheel lightens the contact and therefore the stress on the inside axle. I believe very few cars with welded live axles have difficulty with broken axles (no CV joints in this equation). This lever action is the reason why live axles with open diff don't work well on the track. Depending on the sharpness of the corner radius, the rear looses traction in the corner...sharp corners have less traction.

Driving style is slightly different from any limited slip, in that a condition known in the literature as "corner entry understeer" must be overcome. Simply, with the equal traction of both wheels in full contact at turn-in, the front developes understeer.

Your style of driving will be to slightly "upset" the car to lessen the traction on the rear wheels. We did it with a simple "burp" of the throttle when turning to get the grip lessened in the rear, and increased in the front. After turn in, throttle will control the line thru the corner.

I have used a welded diff for many years, but only in a live axle cars. I have no complaints other than the inherent roating and unsprung weight that the gears and welding create. I would prefer a spool which is lighter, but most of the smaller cars don't have that option.

I have seen some IRS cars with welded diffs in endurance races break wheel studs, I assume from the increased stress of cornering. Their inside wheel is lightened by weight transfer with out the lever action the solid axle has.

Other than the corner entry understeer, manouvering the car is the only negative issue. Floor jack works in the garage...Car skates would also work. At the track, MAKE SURE THE ENGINE RUNS TO MANOUVER THE CAR.

Incidentally, we never drive the car on to the trailer...use friends and relatives to push the car. I like the clutch to get worn out on the track, not trying to get the thing on the trailer. It's not difficult to push in a straight line on to the trailer.

I hope this helps in your choice.

Good racing.

Bill