Welded differentials

[jcg3813]

I like to know the pros & cons of using them, what you people suggest ?.
Thank you.

[Dano77]

pros,both wheels apply power,con,both wheels subtract power...you will most likely develope a massive push until you smash the throttle enough to break the inside wheel loose,then balance becomes your best friend. You can overcome the cons with stagger but we turn left & right so weigh your option at the track. Pro,wayyyy cheaper than a quaife or detroit locker,con,still pushes. good luck.
Dan

[Weaver7]

Like Dan said it will make the car push like a stuffed pig however it will teach you how to rotate the car properly!! :) Had one in our first Gen RX7 only ran it for a couple of races though.

Bill Weaver
ITS RX7 #63

[Tak]

Pro's of a welded diff: Cheap. Almost as fast as a fancy diff IF the car is set up right. You'll never lock up just one rear tire...
Con's: Properly set up cars for a welded rear end will wear tires faster; they will be scary to drive over the range of high speed and low speed corners; if the welds fail, it's bad; if it's not set up right, you will get lots of understeer (as in hello wall); impossible to roll the car around in the paddock, driveway, garage etc.

For a road coarse, a car with a welded diff needs to be set up like a go-kart--that is it MUST lift the inside rear wheel when going around corners. This is typically done with significant rear anti-sway bar. Suspension springs must then be selected that will result in a somewhat balanced car when it's on 3 wheels. A roll cage structure that really stiffens the chassis will help tremendously. It will eat rear tires (because only one is on the ground while going around corners). Good damping will also help. If you are not afraid of oversteer, it can be fast. Note that extra care is required in esses and chicanes--the car will require more time to transition from one direction to the other than a car with all 4 wheels on the ground (the suspension physically moves more and transfers more weight around in a welded diff car).

FWIW, many many moons ago I got to play with a formula SAE car that could run either a Torsen or a spool. Properly set up, the spool was as fast as the torsen around an auto-cross type track. Around a faster track, it had too much oversteer with a spool. Very comfortable with the Torsen though.

Hope that helps,

Tak
#29 ITA SFR SCCA

[Tak]

Whoops, must qualify my previous response--all that applies to a rear wheel drive car. I haven't got the foggiest about setting up a front driver. I expect you still need to get the inside drive wheel off the ground, but have no experience there.

Tak

[RX3]

I have run a welded differentials for many years on a rear wheel drive car and like it.

[shwah]

With this post being in the VW/Audi forum, I will guess it is in reference to fwd.

They work great, cost less than 'real' differentials, but do require/allow some different setup and driver habits.

Understeer is not the problem you might assume. Just get your foot on the loud pedal and it will go where you point it.

When I started using one, I got myself ready for the higher driver effort/concentration that would surely be required to tame a cantankerous fwd locker. In fact it is much easier to handle than you think - except in the paddock.

[Drew Aldred]

+1 to what Chris said above. I've driven both on a VW and prefer the welded diff. Not as much push as some people will tell you. Point it where you want to go, stomp on the gas and hold on, because you are going right NOW !!!

Pushing it around in the paddock is a pain with the welded, be careful not to backup while driving and make too sharp of a turn - easy to snap an inner CV joint.

[chewy8000]

I run a welded diff and love it. It does push like crazy, but you learn to control it.

Pro's:
1 - you can brake incredibly late and deep.
2 - With good rain tires you can win races.

Con's:
1 - Pain in the arse to move around in the paddock.
2 - plan on eating up a few CV joints over the season.
3 - If you early apex a turn don't lift! Stay on the throttle or you'll end up in the wall.

Just my experience in the rabbit GTI.

[shwah]

replace 'lift' with 'left foot brake' for most situations

never broke a CV - of course now I will break 5 this weekend!

[jcg3813]

Thank you guys for all your inputs !. I forgot to say that this is for a 84' VW Rabbit. We have a tremendous inside wheel spin coming off the corners and this will be the easiest and cheapest way to fix this problem .

[Knestis]

My next "sprint" gearbox for the Golf will have a spool.

K

[Grumpa]

My next "sprint" gearbox for the Golf will have a spool.

Kirk,
Any particular reason for the spool? Rotational mass?

I ran my first race with a welded unit a couple of weeks ago and loved it. Gotta change the setup to some softer front springs to get the car to rotate better, but I like steering the backend of the car, as opposed to the frontend, with the loud pedal. VW's are a lot more fun to race with a little oversteer, and they can really brake deep.

[OTLimit]

You would have to fight Chris tooth and nail to removed the welded boxes from the ITB and HP cars he drives. Hated the Quaiffe. Haven't seen good evidence that there is a faster way with the VWs that fits his driving style.

[RacerBowie]

My next "sprint" gearbox for the Golf will have a spool.

K

Good thing I've already driven the important sprint in Pablo. Ugh.

[seckerich]

A spool or welded is usually the last result of failing to get a proper limited slip. Proper being the key word. An LS equipped car will always have less power loss through the driveline. Can't fight the physics of dragging the inside wheel.

[Knestis]

I put a lot of stock in slip angles - the reality that the tires REALLY aren't ever completely hooked to the ground.

My opinions are influenced by the fact that I'm a curb-jumping, grass- and dirt-hooking type. The point at which the inside wheel is on a low/no friction surface (grass, mud, air) one of the primary arguments against the spool go away. And they are minimized to a significant degree in other conditions.

Recognize too that this is another Old School moment for me. It's what we had, so we got used to it. They can be diabolical in the wet.

They also don't break (the spool option, that is) and are lighter, both in terms of mass and rotational inertia.

K

[shwah]

Toss that spool on the scale when you install it Kirk. The standard version is heavier than a welded. I do think there is a lighter version available today though. That said, the durability and servicablility of the replaceable spline shafts are enough justification for me to use an honest to goodness spool next time around.

For welding up a diff, be sure to get it crack checked by an expert before and after the process. It is quite common to find them not up to the task before you touch them, letalone after welding.

[nsuracer]

A driver who is just a whole lot faster than me (not mentioning any names but his car is yellow and has a 4 on it) said that a locked diff forced you to keep your foot in the gas (fwd). That being said, I hated it. My current car has an open diff. I may not be as fast, but al least I don't fall out of the car at the end of the race.

[OTLimit]

A spool or welded is usually the last result of failing to get a proper limited slip. Proper being the key word. An LS equipped car will always have less power loss through the driveline. Can't fight the physics of dragging the inside wheel.

May be true on a RWD car, and Chris would probably agree with you. However, that has not been our experience with the FWD VWs.

[Ron Earp]

Seems to be they'd have to be slower for reasons as Steve stated. Of course it could be the increased traction helps the corner drive so much that it negates the higher driveline losses.

I just put a welded diff in my car for the Daytona race. It isn't that I wanted a welded in the car, just that the 3.56 gear I wanted to put in the car is coupled with a welded setup spare diff. Easiest to simply bolt the whole thing in place. I imagine it'll be a pushy car, hope it doesn't have any life threatening handling characteristics.

R

[seckerich]

I had the same comments from a certain Swift driver in his production car. Top runoffs driver as well. Built him a good limited slip and he noticed the difference immediatly. You can set the car up so you are faster, but there is always a little more left on the table. A comfortable, confident driver is fast despite the setup. Personal feel.

[Ron Earp]

Steve, got any quick last minute tips for setting up a Z car with a welded that generally doesn't wear a welded? I imagine softening the front sway a bit would be a good first step?

R

[betamotorsports]

Here on the west coast most of the ITS guys who ran S30s used a welded diff. The setup differences from a LSD rear diff are:

300F / 325 or 350R springs
1" front ARB, 3/4" or 5/8" rear ARB.
Front toe: 1/8 to 3/16" out.
Rear toe: 1/8" in.

[JeffYoung]

John, thanks. I'm still trying to get Ron to buy your Koni 8611 kit....eventually I will win out.

Right now he has 600 lb front springs and 300 rear, not sure about bars (no rear bar I think) and toe.

I smell massive push. Your thoughts?

[shwah]

I had the same comments from a certain Swift driver in his production car. Top runoffs driver as well. Built him a good limited slip and he noticed the difference immediatly. You can set the car up so you are faster, but there is always a little more left on the table. A comfortable, confident driver is fast despite the setup. Personal feel.
Did Woody have a spool or a diff in the podium/rain race?
Chuck runs welded in the Rabbit, and as mentioned Chris does as well. I thought that the whole G podium that year was fwd welded - maybe I was wrong.

Chuck tried some 'real' diffs back in the ITA days with disappointing results.

[betamotorsports]

Far be it for me to criticize someone's setup, but 600 lb. in front springs on an ITS S30 is at least 200 lb. in. higher then I've heard anyone run, and that includes the Chet Whittle/Keith Thomas ARRC winning car. I do know of a few guys down in Australia running 600/450 on their S30s but they have a lot of chassis reinforcement done and are definitely beyond IT levels of prep.

Maybe it works and more power to the folks that make it work. Its always better to try something different with the chance that you'll make your car faster then to copy and know your car will be just as fast.

[Ron Earp]

425lb F / 350lb R.

I think 600F would be far beyond the stiffness of the chassis. 425-450 is pushing it I bet.

[JeffYoung]

Not to disclose any of your secrets but I thought you were higher than 425?

I tell people about the 600s in the front of my car and they say the same thing...won't work. Seems to though.

[OTLimit]

Chuck tried some 'real' diffs back in the ITA days with disappointing results.

Back in the day, both Chris and Chuck bought Quaiffes; after doing what everyone said and trying to make them work, and draining and dumping lots of sparkly gear lube, they finally gave up and went with the welded diffs. It was an expensive lesson.

I do believe that Chris managed to break some type of lsd, but can't remember which one right now. If he believed that the welded diff was causing him to lose important races, I'm pretty sure that I would have paid for something else by now.

[shwah]

All this said - we are looking at running a Kazz lsd at the 25 hour, in an effort to make the setup as easy on the Jetta parts as possible. In that case Chuck, Chris and I should be able to give some comparison feedback between the two setups (of course need to finish building the car first...)

[racer_tim]

I've only lost 1 CV joint while running the welded diff for 8 years now. I change out the entire 1/2 shaft assembly, including CV's and hubs every year as "standard" maintenance.

[Ron Earp]

Not to disclose any of your secrets but I thought you were higher than 425?

I tell people about the 600s in the front of my car and they say the same thing...won't work. Seems to though.

450 it says on the spring, looked tonight. My bad. Not any secrets around here - if folks like to go as slow as I do....

Seriously, the 450s feel great in the car and were the single best thing done to the car, replacing the 325s that were in it. Now working on that other stuff like struts....

R

[racer_tim]

HEY, this is the VW forum. We don't do RWD in this section. All you Datsun/ Nissan guys, get over to your own forum.

hehehe

[veeman]

I just got the chance this weekend to try a welded diff in the rabbit. I read a lot of info here and talked to a few other racers before installing it, but I'm glad I did.

I was initially nervous about the stories I'd heard about the "push" and adapting driving styles based on the locked diff, but it really wasn't that bad. After a few laps, I was used to the "get on the gas" through the corner thing and was loving the grip.

I need to do more work on the suspension to dial in some more rotation, but that'll come soon.

I've driven rabbits with the open diff, limited slip (Quaife) and now the welded diff and my vote is with the welded setup. The only thing I don't really like is having to muscle the thing around in the paddock / false grid.

[racer_tim]

Yes, it does require "Popeye" type bicepts to make 90 degree turns in the paddock, but you need to learn to setup your paddock space so you can just "drive in, drive out" without making those really slow 90 degree turns.

[loopracing]

We've used welded for the last 13 years with good results. As far as the "popeye" arms, I'd suggest a larger steering wheel. A 14" should do the trick. Poor man's power steering.

[loopracing]

If you want to keep CV's then don't make 90 degree turns in the paddock either.
If anyone needs one welded, email me, I can turn it around pretty fast if you want.

[chewy8000]

I just started racing this year and all I've driven is a welded diff. I have no idea what anything else is like... Any of you other rabbit guys running the front sway with the welded setup? I have been told by many people not to, but one of the DC region rabbit zen masters swears you should keep it on. Thoughts?

[racer_tim]

I run a front and rear bar with my welded setup. I did the same with an open diff. The major difference, is that I don't loose traction on the right hander turns. With the open diff, I used to hear the "chirping" of the inside wheel trying to get traction.

With the welded diff, you get traction on both front wheels all the time. Keep in mind with a welded diff, that the inside tire travels the shortest distance, so it feels like it's "pulling from the inside".