Welded Diff on a FWD road Racer?

We've got the power figured out on the Dirty Escort, but now we have to be able to put it to use. For those of you not in the know, it's an '86 Escort with a turbo Zetec in it. We were turning some fast laps at Rockingham, but absolutely lighting up the inside tire exiting a few of the corners. Anyone here road race a fwd car with a welded diff? Pros and Cons?

I've never done it, but it sounds like it would be interesting...

I'd bet it develops unbearable understeer.

Wouldn't that cause a ton of tire wear? Especially on race tires? I've never heard of it being done before but I'm sure that I'm under-informed.

I would think that boost coming in would mean a ticket to the Armco on the outside wall.

Talk about understeer Works ok on ice though.

I have read about IT guys doing this. Maybe search http://www.improvedtouring.com/

Or try searching http://prodracing.com/prodcar/ -- might be something there, too??

it is a highly recommended thing to do over on the Chumpcar board.

can you not fit a limited slip diff to that trans? thought the svt focus had lsd. not sure though. or is it that you have an lsd and it isn't doing well enough?

Welded diff on a FWD car requires a totally different set up then an open diff as well as a different driving style. Set up differs by car and suspension design and every drivers is different. I know there are some postings at IT.COM. Some swear by it. I can't comment myself as I have only driven a welded diff RWD car.

Need an Auto Power bolt-in cage for the Escort? ... I gots one for sale

What about those Phantom Grip deals that put pressure on the spider gears? Might be a cheap and easy solution that's not going to work as well as a real LSD but also won't be totally locked up like a Lincoln locker.

The Phantom Grip does help. Biggest help for a FWD car is to keep that inside wheel on the track, Stiffen the suspension, especially the rear. Learned this from running My ZX2SR at track days. There are a couple of limited slips that can be fitted to the car. Biggest change is different axles.

I'll try to answer all the questions posted.

A limited slip diff will "fit", but I don't think anyone makes one for this trans. The trans is out of an '88 Escort GT. Supposedly there are a few LSDs that can be modified to work, but I don't know the details.

Sorry, don't need a bolt in cage, the car already has a cage welded in.

I've thought about the Phantom Grip, but it seems pricey for what it is. I was hoping for a resounding "yes" to the question of welding the diff, so I wouldn't have to think about more expensive options! I guess what I might do is pull the diff from the original 4 speed that came out of the car, and do some comparisons. Ideally I'd like to have an LSD, but rather not spend the money for one or have to modify the crap out of it to make it work.

In reply to 16vCorey:

Do you have a spare? can always weld one up, and if it doesn't work, go back.

I wish I could help more than that, but haven't raced a FWD car to suggest any alternate set ups.....

I've got the 4 speed that came out of it as a spare. The ratios totally suck, but I guess it would give me a pretty good idea what the handling characteristics will be.

Weld up one tooth on each spider gear (not to each other, just fill in the tooth). Should allow for some rotation until the other gear hits the filled in tooth then locks up. Of course, this could be a terrible idea...

slefain wrote: Weld up one tooth on each spider gear (not to each other, just fill in the tooth). Should allow for some rotation until the other gear hits the filled in tooth then locks up. Of course, this could be a terrible idea...

Diff go boom quickly with this approach, the gears are very hard and will chip.

I'd recommend against it. My self and Tom Spangler (occasional poster here) used to race ITC Fiesta's (as in 79-81 type). I had a Viscous LSD from a Euro Escort RS turbo and he had a welded diff. While we valiantly battled each other for last place my car definitely had the edge. While my car actually handled OK when it wasn't munching on it's own engine for lunch (can cars have Lupus?) his car loved to go in a straight line, well as much as probably 60 hp loves to go straight, but show it one of those bendy bit's of track and it threw a hissy fit. Turn in? Not on the menu today sir. It was absolutely horrible, plus the extra stress on the driveshaft and hub meant it had a high appetite for those parts, once leading to a wheel exiting stage right over the catch fencing and landing on a car in parking lot. Welded diff for loose is fine, but on sealed surface I'd stay far far away. Now you may have a different result and an excess of power can do wonders for overcoming other shortcoming, but I'd not go down that road.

I once drove an AWD Mazda 323GTX that had the front diff welded at one of the early challenges. (I think it was Lee Glaser's?). I turned in, the car didn't. Through a cone wall I went. Some Pro driver, huh?

Not too mention that they are a bitch to drive at low speeds (I believe the term is "wrist-breaker") You can't bribe the things around the paddock when being pushed. Then there is the fact that you can break CV joints with the quickness.

Friend was helping driver-consult with a husband/wife team who raced a 510 in production. The wife was coming along quite well, but kept complaining about terminal understeer followed by terminal oversteer. This was different than the previous outing she's had with the car. Finally, my friend corners the husband and asks about any changes with the car from the last event. He eventually mentions the welded differential.

My friend tells him to grab a non-welded diff housing and change it before Sunday's race. He balks a bit and complains that he was told that was the fast setup for a 510, etc. Finally he relents after the wife loops the car again and comes in crying because she thinks it is her driving.

Sunday comes and she drops 2-3 seconds a lap in the first practice.

Welded diffs had their place as a poor mans limited slip, especially in the old days when tires weren't as grippy and suspension wasn't as sophisticated.

Welded diffs create a point and shoot car. Corners are squared off to keep the wheels turned only a bit at a time. With a turbo FWD car, with a welded diff you'll need to left-foot brake like a mofo and keep your foot in the gas to keep the boost up. The loads generated on the axles in this situation are not pleasant as you can imagine (drag launch from each corner essentially).

For Chumpcar, the price of the car means that you can't afford a $500 limited slip, unless the car came with one from the factory (or you can bodge one in from a more common rig in the yard) So the options are terminal inside wheel spin (meaning you have to drag race from corner to corner, coast through the corners and hammer the gas once the wheels are straight) or a welded diff and hope your CV joints/differential survive and you can put the power down earlier.

In reply to turboswede:

FWIW- I saw two Alfas break axles in one weekend- both were welded. One lost a wheel (the structure of the older axles). I'm going to try to go the other way- set the axle up so that limited slip wont be needed.