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Discussion Starter · #1 ·
does anyone use a welded diff on the street? I am not to sure about using the PG, and I am not spending a $1000 on a GURU. So I think I am going to weld the diff. I won't be driving the car daily, but I will drive it often.
 

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Actually, generally its accepted as quite the opposite. Welded RWD cars make for some horrible handling unless you want to drift every corner.


I have considered it, but I also want to be able to race import drags. NHRA doesnt approve of the welded diff, and they WILL check.

A better option may be to weld the diff pin in place. Still an open diff, but prevents the classic diff pin shearing off and trashing everything in the process.

Thats what I did a while back, still haven't killed this tranny after all the abuse it's been put through. Trust me, it's a TON. The spider and side gears were literally perfect. If you plan to do this, may want to buy some brand new ones from mazda. IIRC you can get them all for somewhere around $50-75



 

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SixSick6 said:
Might want to also check into what the track you go to says about that as well. Nobody likes someone who has to do a 9 pt turn in the return lane to come back to the staging lanes.
About what? If you're referring to welding a diff pin, it changes absolutely nothing in the behavior of the car. you'll still have one tire fire, it just keeps that pin from grenading with too much force, thats all.

What people hate even worse is someone that pukes tranny fluid all over the track, has to get towed and everyone waits for 10 min as they clean up your cars blood.

The diff pin being welded gives you more of a safeguard against that.


But FWIW our track has so much space, i dont know that youd ever need to turn a corner as sharp as you're thinking.
 

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I have a welded diff in my skyline, its rwd, its lovely, except every 6 months for warrants, and the real wear and tear on my driveway and freshly sealed road. it shudders turning slowly on full lock, but just squeels under heavy throttle. you dont drift every corner, you just come in under brakes, and move from brakes to turn in gradually without any coasting (trail braking) add some extra anti sway on the rear to ensure that the front wheels have more grip, keep the car balanced, and you are away laughing. cant imagine it being good in fwd, but have no experience in that, so if you say so then cool. only time its no good is down hill off camber in the wet, when if not properly balanced it will understeer. also in a fast bend > 120kph if cornering moderately it will make the car rock/buck as you turn, a bit freaky...

try it on a beater, (perhaps damian will volunteer?) and let us all know.

fred.
 

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Discussion Starter · #7 ·
what about a welded in diff pin with the Phantom grip? also if I welded the diff pin in, I wouldn't be able to get the PG out unless I broke the weld?

What type of welding would you recommend to do this? My friend has a Mig welder, but I am not sure if that is strong enough?
 

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ehhh... phantom grip still seems to have problems with 1 tire fire from what I've heard.


you could remove/install the PG with it welded, but you need to have the gears machined first before welding that pin in for good.


My friend did it with a big 230v mig. I would recommend tig or arc though, but the mig was fne for me.


What I did was remove the diff pin, put it on a bench grinder and ground a bevel on the ends of it. then i took a die grinder and ground a bevel in the case at the end. This left a nice v groove to fill with weld when I put the pin back in.
 

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i also used my mig, its the biggest single phase unit(230v) that cigweld do(did(transmig 185)). as long as you wash the oil off/out very thouroughly its simple and as long as you obtain proper penetration, it will be strong. an engineer friend of mine did some rough calcs on the strength of mine(based on the lowest grade of weld), and it simply cannot break in that region without detroying everything around it. i recommend using an anti splatter on everything near, and some sort of leather cover to stop it finding its way to the bearings etc... i was rough on mine, and when i washed it out, it was crunchy by hand while washing it for a while. it still goes though, and has suffered a lot of abuse.

fred.
 

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Yeah, but thats a full on track car that will never be driven on the street.
 

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eric and i both have our diff's welded solid. eric has a treated 3rd gear as well, and i might have a custom gear set made if it proves to be a failing component.
otherwise, a nicely welded tranny so far has made erics fe3t mx3 go 1.5 60' reliably and consistently.

this isnt something i would suggest for a day to day car, because even pushing it is harder with a spool. but really, what else are you going to do? phantom grip or the lsd from australia only other options, and its hard to say what they will hold up to.
 

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there was a fe3t mx6 in Oz, that used a welded diff, apparently he was always going thru cv's and hub bearings, but this was used a daily. dont know if you would have such problems with yours being a race car.
 

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the rear of my skyline has CVs and they are fine so far, its shock loading that kills them anyway. i still cant see the wheel bearings suffering because of this.(it was discussed before somewhere)

DJ jake : how does it drive with that in the front? turning? shuddering? lots of understeer? none of the above?

fred.
 

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Discussion Starter · #15 ·
Well I won't be driving the car daily, but it will be a street car. I think I might just get it welded. It will be a lot cheaper.

I guess third gear is the weaker one?
because I messed up 3rd on my first trans, and on my second trans it completly sheared off.
 

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^^ yes thats been a common problem. it seems to be what commonly starts to break once the diff is taken care of.

fred, your skylines rear cv's wont endure the kind of stress with a spool like a fwd'er will. when turning with a locker in the fwd setup, the inner cv will make some noise, clicking due to it being forced to try and take an equal path through a turn. thats where most of the wear occurs.
the front end tends to dive and understeer. this isnt recommended for a street car.

ill also add, you usually do not retain your speedo any more once you weld the diff. depending what kind of method you use, the heat generated by it typically melts the plastic speedo ring. its best to cut it off prior to welding so it doesnt get all over the race
 

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hmmm... when i had the pin welded my speedo ring was okay. of course this wasnt tig or anything, thats what really makes the heat.

i still think im going to weld mine once it breaks.
 

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yeah, i realise that they arent sliding back and forth as they rotate as much as yours do, same goes with the drive shafts uni joints being a truly irs rear the engine vs shafts vs diff dont move much.

so when you wind on the lock coasting you get a braking effect? i can park mine on a slope with full lock and not use the handbrake :)

i guess the thing to do if you were going to try to street it would be to set up the suspension such that when powering round a corner you lift the inside front a little, thus allowing it to slip and generating some thrust for you. ie lots of front swaybar and no rear. still wont help while parking though.

i'd like to see/feel it in person just for the experience.

fred.
 

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rebel2k4 said:
hmmm... when i had the pin welded my speedo ring was okay. of course this wasnt tig or anything, thats what really makes the heat.

i still think im going to weld mine once it breaks.
it depends how you weld it together. some say keep it cool, and weld in short intervals, some say get it hot with a torch, and quickly jump on it with a tig.
either way, welding just the pin wont bring that much heat across the speedo ring anyways. the plastic isnt THAT soft, but if your bring the heat down on the side gears, it will most likely melt it.

who needs a speedo anyways
 
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