HOW TO DO AN ADVANCED SEARCH.

Mon Jul 08, 2013 3:56 pm by Admin


For the benefit of 944Hybrids users there are two search functions available for you to use.
The purpose of this sticky is to explain the "Advanced Search" function because it is much more powerful and is the best choice when researching information.

When you log on to the site a list of options is shown in a line at the top of the page. One option is labelled "Search", use this option (NOT the search box lower down on the right).

After you click on the upper search option, a drop down box appears. At the bottom of this box is a radio button marked "Advanced …

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welded differential

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welded differential

Post  tooms351 on Mon Nov 28, 2011 6:45 pm

Hi All, has anyone tried this? I have a spare trans from an 85.5, I'll get it welded tomorrow and swap trans. this weekend for a chin event on 12/11. It's an 86 turbo for track use only (now!) I'm tired of that peg leg and not pulling out of turns. Just wondering if anyone has tried it, thanks.
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Re: welded differential

Post  87-944S on Mon Nov 28, 2011 7:46 pm

Welded diffs are usually for straight line drags, since your outside wheel will want to turn faster than your inside, on a road course, a welded diff is not your friend.
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Re: welded differential

Post  tooms351 on Mon Nov 28, 2011 8:17 pm

thanks but I'm gonna try, seems like the 911 guys try it and say it helps. Can't be worse than spinning the inside rear tire bald while a miata pulls me outta the turn!
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Re: welded differential

Post  docwyte on Tue Nov 29, 2011 8:38 am

You're not going to be happy and you'll have a ruined diff. Welded diffs are ok for drag racing, not for road course driving.

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Re: welded differential

Post  tooms351 on Tue Nov 29, 2011 5:06 pm

Hey Doc, thats quite possible but I have to try something, I'm hoping I can make it work with a more agressive driving style. I noticed you on u tube and will watch after this, are you running an lsd or an open diff?
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Re: welded differential

Post  87-944S on Tue Nov 29, 2011 5:40 pm

You have 3 choices, open diff - not good for road course, best suited to unmodified mild street cars, LSD - excellent choice for road courses, pretty good for autocross, always good for the street (depends on lockup} ATB (automatic torque biasing) - excellent for the street, pretty good for road courses, killer for autocross

Don't do the welded diff, not suited for these cars, basically it is equivalent to a spool for a drag car, but not as strong.

Just my 2 cents, I have used them all in one car or another. Did a lot of straight line drags when cars built for that were cheap, posi-traction was great for dragging, really sucked for around town, but had a car or two like that, went through tires pretty quick. That was with a 9 inch Ford rear end, I suspect your transaxle will grenade sooner or later with a welded diff.
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Re: welded differential

Post  docwyte on Tue Nov 29, 2011 5:46 pm

Tooms, I'm running the factory lsd Turbo S transmission. I haven't found it to be much of an issue with peg legging on the road course. I do spin both rear tires coming out of tight, low speed corners.

I'd look around for a used lsd turbo transmission. Either a 5R or the turbo S AOR transmission.

You can add an lsd to your current transmission, like a Guards diff, but they're quite expensive. Guards quoted me $2800 for their diff and that wasn't including installation.

A Quaife diff is cheaper, but I'm not sure they make one for our car and it's not an lsd, it's a torque biased diff.

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Re: welded differential

Post  tooms351 on Tue Nov 29, 2011 6:16 pm

Too late, it will be tig welded by tomorrow. It just comes down to cost, I had the trans as a spare, and its tough to beat a $40 weld job, I will post up after the 12-11 Sebring event. Doc I watched your track vids, saw you get squirrelly a couple times in the turns, but pull right out. My problem was catching a low hp car in the braking zone having to wait to get on the gas, and still spin the inside tire, then not catch up till the next turn. (point by on straights). The right rear tire is shot while the left is still 50%. I'll mess with tire pressure and shocks and as usual try to make it work, should still be fun!
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Re: welded differential

Post  87-944S on Tue Nov 29, 2011 6:44 pm

Wow, that is too much for a Gaurds diff, my ATB was about 1400, plus a painful 200 bucks for a gear to drive the oil pump. That was 2 years ago, maybe prices have gone crazy, Quaife's are excellent, used them in my VWs, bullet proof, 2800 is insane.
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Re: welded differential

Post  docwyte on Wed Nov 30, 2011 8:34 am

Tooms, good luck and let us know how it turns out.

87-944S, yeah that $2800 price is outrageous. It does include the cooler drive gear at least.

When he told me how much it cost I about died. I'm used to how much a quaife/peloquin diff costs for a fwd VW ~$800. Figured with the Porsche tax the Guards diff would be $1500 or so.

Here's hoping my factory diff lasts a long time. Luckily the factory diffs are rebuildable...

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Re: welded differential

Post  948 on Wed Nov 30, 2011 9:06 pm

Many people have tried this, obviously not a new idea. Some of the things to expect:
  • Under-steer in the dry

  • Over-steer in the wet

  • Change in overall handling

  • Extra strain on other parts which may lead to early failures

  • Better power out of the corners


I would save up for a used factory LSD....
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Re: welded differential

Post  tooms351 on Thu Dec 01, 2011 9:10 am

Thanks Doc I will. Hey 948 I'm looking for better traction out of the turns and hope getting on the gas sooner will help rotate the car. I don't know for sure but with the power split between two wheels instead of all the power going to one wheel, it should be easier in the drive train? I hope. Are you from southeast PA by any chance?
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Re: welded differential

Post  docwyte on Thu Dec 01, 2011 9:28 am

I think the car is going to be a handful in the corners. The open or lsd diff allow each wheel to turn at different rates as needed in the corners. With the diff welded the car won't be able to do that and will want to crab walk around corners...

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Re: welded differential

Post  tooms351 on Thu Dec 01, 2011 4:47 pm

I've heard it will drive differently, I'll try getting on the gas sooner and a bit more aggressively hoping to slip the inside tire while the outside tire grabs, helping turn the car compared to an open diff. Anyone agree or disagree? I'll take it easy the first few turns till I get the hang of it.
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Re: welded differential

Post  948 on Thu Dec 01, 2011 8:17 pm

As Doc, and I, have mentioned your car will handle quite differently, probably not for the better.
Contrary to what you believe the welded diff will prevent the car from turning into and through a corner, under-steer.....if you make it through the corner then your welded diff will reward you with some straight-line traction.
I think the negatives far outweigh the positives on this one...but if you don't try you can't learn study
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Re: welded differential

Post  tooms351 on Fri Dec 02, 2011 4:36 am

Gee thanks there Buddy, I'll have to take that as a you disagree! I don't know how many welded diffs you've raced with but it has been done before. You sound like some knucklehead telling me I can't stick a v8 into a 944! I can only hope you're not in front of me WHEN I do power out of that turn!


Last edited by 944-LT1 on Fri Dec 02, 2011 7:36 am; edited 2 times in total (Reason for editing : moved)
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Re: welded differential

Post  944-LT1 on Fri Dec 02, 2011 7:45 am

Woah. Everyone is just trying to help you here. You asked if anyone agreed or disagreed...
tooms351 wrote: Anyone agree or disagree?

Paul just said what to expect and left it with an encouraging line....
948 wrote:...but if you don't try you can't learn

When Paul says something, its highly concentrated education/experience oozing out (aerospace engineer). He simply stated pros and cons for ya.

....Please be nice to our resident gurus. Very Happy Very Happy
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Re: welded differential

Post  Dawgz83948 on Fri Dec 02, 2011 9:29 am

Too bad nobody makes a detroit locker for the diff in the 944...... Best of both worlds..
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Re: welded differential

Post  BW_Matt on Fri Dec 02, 2011 10:31 am

When you are going through a corner your wheels need to be turning at different speeds as they are carving different radii through the corner. A locked diff means one tire is scrubbing whenever you are turning, and that force is what makes your car want to keep going straight- understeer. People that run spools in road racing/ autocross typically set up their cars so that they lift the inside rear wheel on corner entry to avoid the scrubbing and understeer. What gives better grip- 3 tires or 4?

If you use your car for anything other than drag racing it simply compromises too many aspects of the vehicle dynamics to be worth it.

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Re: welded differential

Post  948 on Fri Dec 02, 2011 7:10 pm

tooms351 wrote:I don't know how many welded diffs you've raced with but it has been done before.

Yes, it has been done before...we covered that.
I have only made 2 welded diffs in my short time on this planet. For my FWD VW, auto-crossed and drag raced, back when I was a poor Collage kid... It did great at the drag strip, didn't cost anything but did not do so well around the cones. As soon as I had some money, read: credit card, I bought a Quaife ATB diff. I used that in various 020 based transmissions for about 8 years and sold it for damn near close to what I paid; the second best purchase I ever made for my 020 trans....the first was a straight cut gear set.
Oh, the second one I made was to replace the first. It is quite difficult to make robust welds on old, oil soaked case hardened steel...

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Re: welded differential

Post  tooms351 on Sat Dec 03, 2011 3:08 pm

Oh man, if I had the money I would! I have another track car a 66 Mustang set up like a trans-am car that I might drop two grand on a front suspension. (wish I could just weld that) A friend of mine who owns a german auto repair shop for like thirty years suggested this after I complained about the price of a new diff. I really appreciate everyones input! I was hoping someone with a spec 944 or scca 944 would post up. I hit a bit of a snag, waiting for output shaft seals so I'll be busy monday.
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Re: welded differential

Post  laptop_geek on Tue Dec 06, 2011 10:21 pm

Drifters use this trick also, it allows them to lose traction in the rear sooner and drift more easily. Your car will want to do the same. Hit up a local drift or drag event to see what a welded diff does.
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Re: welded differential

Post  tooms351 on Wed Dec 07, 2011 10:15 am

I've been looking at 944 spec and 944 cup for sale ads and noticed a couple welded diffs in the description, I just think some guys are keeping that info to themself while at the track.
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Re: welded differential

Post  948 on Wed Dec 07, 2011 6:27 pm

Good link on the topic
http://www.944spec.org/944SPEC/forum/arizona/4103-need-some-tranny-advice
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Re: welded differential

Post  tooms351 on Wed Dec 07, 2011 8:43 pm

948, thanks for the good read! I wish the one gent got into set-up a little more. The only real adjustability I have is shocks and air pressure. I was looking on ****list they pretty much said the same, but they felt higher hp cars would fare much better than their 150hp specs. One other thing on my side is it's HPDE so no side to side especially into and out of turns, also tracks with long sweeping turns like Sebring (this Sunday) Watkins Glen was also mentioned, as easier and faster than tighter tracks.
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Re: welded differential

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