welded center diff

[rc90gsx]

anyone ever run one of these on the street? if so whats it like on a day to day basis? how annoying could it be?

 

[GRNDSM]

It all depends on the person. Some think that it is OK, other hate it. I am one of those who hates it. That is why swap in and out welded vicous coupling for welded center diff effect anly 1/3rd the swap time.

Leon
RR

 

[rc90gsx]

you lost me a little with those last couple of lines. please explain more. why do you hate it. im the kind of guy who removed my working a/c, removed my working power steering, and generally sacrifices a few daily comforts so i dont think it would bother me but id like to hear everyones likes and dislikes. also im married with a child so budget comes into play often in my world.

 

[GRNDSM]

Swapping in a welded viscous coupling has the same effect as welding the center diff. It is easier to weld and to install. However, you are still using stock center diff, which is not all that strong and can brake. That is why I am using a welded VC with an upgraded center diff (Speed Design 4 spider gear unit).

I HATE everyday derivability of a welded center diff/VC mode. But that is me...

Leon
RR

 

[rc90gsx]

what kind of issues do you encounter everyday while driving with a welded diff? what bugs you the most? sorry to be ask so many questions id just like to hear from someone who has driven with the pros and cons. thanks

 

[90GSX]

I have a TRE Spool, drive it semi-daily. The rear tires chirp a little in parking lots, but on the highway it's not noticable.
It just depends on personal preference.

Good luck,

 

[GRNDSM]

rc90,

EVERYONE has different opinions about it! You are just going to have to try it out. But it is NOT good for your drivetrain...

Leon
RR

 

[4pistons]

I've probably got 30-40 thousand miles on my welded diff. I even Autocross with it. The ONLY time you notice it's there is negotiating slow, tight corners. Then the rear inside tire slips or chirps. No big deal. I don't believe it stresses the drivetrain more. I contend that it relieves some stress as it now transfers power to all wheels equally rather than split power through the VC with unequal amounts front and rear depending on how worn your VC is.

DSM center diffs are notorious for the side gear shims disintegrating and failing the output shaft. Did you ever see the shiny semi-worn splines on the output shaft. That's the first indication the side gear shims have gone away. A welded VC will not prevent this as the side gear shim still takes the load. I went through two shafts before welding my center diff.

I have a diagram for welding the center diff if you're interested email me at [email protected]

Rick - '91 GSX

Can we please use "brake" and "break" in proper context??

 

[GRNDSM]

>I even Autocross with it.

You could not have been very competitive this way…

>I don't believe it stresses the drivetrain more.

You can’t be serious?

>I contend that it relieves some stress as it now transfers power
>to all wheels equally rather than split power through the VC
>with unequal amounts front and rear depending on how worn your VC is.

On fast, AWD cars with welded center diffs, most traction transfers to the rear wheels due to weight transfer. Once that happens, you can end up with as much as 100% of torque going to the rear wheels. An extreme example of this would be pulling wheelie. Granted, most of us will not pull a wheelie, but we can still end up with 70-90% of torque going to the rear wheels.

That is the reason why cars with welded center diffs tend to damage drivetrain parts associated with RWD (mostly DS rear axle and transfer case output shaft) at a very high rate.

>DSM center diffs are notorious for the side gear shims disintegrating


Well, the outer spacer/shim/washer tends to wear out, especially if you have a bad VC, have different size tires (front to back), or if you were towed by 2 wheels. But that is why Speed Design improves oil supply to that shim and I am yet to see any problems with them afterwards.

The only times that I have seen inner side shim (the half brass one) go bad, was when spider gears shattered and damaged it.


>and failing the output shaft.

Which output shaft are you referring to?

>Did you ever see the shiny semi-worn splines on the output shaft.

Again, not sure which output shaft you are talking about. The one to the transfer case?


>A welded VC will not prevent this as the side gear shim still takes the load.

A welded VC can allows you to quickly switch to 4x4 mode (same effect as welded center diff) for ether FWD dyno testing or for better drag racing traction.

The problem with ding this is that you are still sending torque to the FWD through the center diff. spider gears. As said before, front wheels do not see much torque due to weight transfer, unless… You brake your rear axle or transfer case… In that instance, your car becomes FWD and 100% or torque goes through your center diff spider gear. This has not been a problem for my Speed Design center diff, but I have now seen several cars which broke factory 2 spider gears in this scenario.

>Can we please use "brake" and "break" in proper context??

Sorry, I have never been good at spelling. And since spell checkers will not pick this one up, you are just going to have to deal with it .


Leon
RR

 

[4pistons]

You could not have been very competitive this way

I am not the best, only done it last year, but I was faster than half the cars there.

On fast, AWD cars with welded center diffs, most traction transfers to the rear wheels due to weight transfer. Once that happens, you can end up with as much as 100% of torque going to the rear wheels. An extreme example of this would be pulling wheelie. Granted, most of us will not pull a wheelie, but we can still end up with 70-90% of torque going to the rear wheels.

With a welded diff or VC there is no variable torque split, it is 50/50 ALL the time. Weight transfers to the rear but not torque. This is one of the big reasons we couldn't do a wheelie. Only part of the torque reaches the rear wheels.

Well, the outer spacer/shim/washer tends to wear out, especially if you have a bad VC, have different size tires (front to back), or if you were towed by 2 wheels.

Yes, all of the above.

The only times that I have seen inner side shim (the half brass one) go bad, was when spider gears shattered and damaged it.

My spider gears were fine and the side gear spacers were still toast. They were smeared to the diff case so bad I could not pound the side gear out with a hammer! I had to get a new (used) diff. And that one had bad side spacers in it, too.

Which output shaft are you referring to?

Technically, in the manual, it is the center shaft. The one that goes into the X-fer case. I have learned to call it the "Output shaft" or people get confused.

A welded VC can allows you to quickly switch to 4x4 mode (same effect as welded center diff) for ether FWD dyno testing or for better drag racing traction.

I drop my X-fer case for dyno testing. Quick and easy.

The problem with ding this is that you are still sending torque to the FWD through the center diff. spider gears. As said before, front wheels do not see much torque due to weight transfer, unless

I assume you are saying "Welding" in that sentence. I have eliminated the spider gears in my diff and welded the side gears directly to the diff case. Much stronger. As I said before, with a welded diff or VC torque doesn't get transferred, it's 50/50. The only device that can vary the torque split is the VC and we've eliminated its function in both cases.

Can we please use "brake" and "break" in proper context?? Sorry, I have never been good at spelling.

I didn't mean you in particular, I see it all over these boards. That is what dictionaries are for. I know it's not electronic but it works!

Rick - '91 GSX
Can we please use "brake" and "break" in proper context??

 

[GRNDSM]

> it is 50/50 ALL the time. Weight transfers to the rear but >not torque. This is one of the big reasons we couldn't do a >wheelie. Only part of the torque reaches the rear wheels.

First of all, given enough traction and torque any RWD or 4x4 vehicle CAN pull a wheelie… Have you ever seen monster trucks? It is a matter of simple physics… Welded center diff or VC gives you 4x4 mode…

With one slight exception, AWD cars with open center diff and FWD cars. VC does would not do much if front wheel would come off the ground or come near it. So an AWD car with an open center diff will be similar to FWD if it looses most of its traction up front.

Second, once you do pull a wheelie or loose 100% of traction in the front, your rear wheels pick up 100% of torque. You can’t see that?

>Technically, in the manual, it is the center shaft. The one >that goes into the X-fer case. I have learned to call it the >"Output shaft" or people get confused.

OK, I have seen that thing go bad on many occasions. Rust is the #1 why it happens. Did you replace your transfer case after the first time that your shaft went?


>I drop my X-fer case for dyno testing. Quick and easy.


I switch my JDM transfer case to FWD. Even quicker and easier .

Leon
RR

 

[4pistons]

First of all, given enough traction and torque any RWD or 4x4 vehicle CAN pull a wheelie… Have you ever seen monster trucks? It is a matter of simple physics… Welded center diff or VC gives you 4x4 mode

Yes, given enough traction and torque. Monster trucks have lots of both, and the advantage of a high center of gravity so it's really easy for them. Only a very few DSMs make enough torque to lift the front end and only the RWDs have enough rear wheel traction to do it. We spread our power out to all 4 wheels to go fast and use relatively narrow tires.

Second, once you do pull a wheelie or loose 100% of traction in the front, your rear wheels pick up 100% of torque. You can’t see that?

OK, now I see what you mean! I thought you were saying the center diff or VC transfers the torque. Yes, I see what you mean. Agreed.

OK, I have seen that thing go bad on many occasions. Rust is the #1 why it happens.

NO,NO,NO,NO,NO,NO!.....Sorry to sound so strong but rust has nothing to do with it. If it was rust the splines would crumble. They are worn, you can wipe the rust away with your finger and see shiny, worn splines. Try wiping rust off any other metal part and see shiny metal underneath. Won't happen. So what could wear those splines? They are engineered for a tight fit and can only move in one direction.

When those side gear spacers in the center diff go bad it allows the center shaft (output shaft) to move back and forth laterally, in and out, every time you get on and off the throttle. The center shaft literally files itself down, moving in and out of the X-fer case gear. THAT'S what creates the rust you see. Notice how the rust is a very fine powder?

On a faulty center diff tranny you can grab the shaft and move it in and out by hand. It shouldn't do that. The first time my center shaft failed I installed a new one without fixing the diff. I also replaced the drive bevel gear in the X-fer case. I didn't know at that time what the cause was. A little over a year later it failed again! It wasn't from rust. That is a hardened, heat treated shaft. It may get rust but will probably never FAIL from rust.

I switch my JDM transfer case to FWD. Even quicker and easier

What is that? I've never heard of it. You can switch it off? Cool! How does that work? Are there any schematics available for it?

Rick - '91 GSX

 

[pneumo]

If I were to run a welded center diff or VC and I wanted to reduce drivetrain stress, either real or theoretical, for daily driving purposes I would run higher tire pressure in the rear and remove as much weight as practical out of the back. That way during low speed sharp turns the rear tires would skip easier, less force needed to break them free. Plus during those turns the weight tends to transfer foward anyway. But I've never done that, so I can't say how much it would help, or if it would make enough of a difference. Maybe someone with a welded diff/ VC could comment?

 

[GRNDSM]

Well, you got the right idea. Most of the cars with "locked" center diffs that I drove, had very sticky tires (Nitto Drag Radials and Toyo RA1s). That made the problem much worse and running very high tire pressure could have made it better (through, probably, at the a cost of strange tire wear pattern). You hear your axles/diffs/tires crack, pop and squeak under sharp low speed turns, I hate it! But one of my friends is perfectly fine with it. So it really does depend on a person.

Leon
RR

 

[Turbocyde]

I really want some clarification on that Jdm transfer case thing that sounds all kinds o' cool tell me more tell me more!

 

[gsxitement]

sorry to bring this one back, but it's got good info. Quick question, when you weld the diff, which gears are you welding? The gears right next to the housing (input, output?) or are you welding the spider gears AND those input, output gears together. I welded the whole job together, all four gears. Is this proper? or do I need to weld my spare center diff. differently. Thanks for the help. No shop wanted to tell me since I was doing it myself. No money, no help I guess. Thanks again.

 

[4pistons]

Check out the diagram http://www.dsmtuners.com/forums/showthread.php?t=173481

That shouuld answer all your questions

Rick - '91 GSX

 

[gsxitement]

thank you very much. I welded it today at work and it went back together fine, so we'll see how it works next week when i get the together. One quick question though, should it be difficult to turn the output shaft? I can't turn it by hand and I haven't tried putting any kind of tooling on it to try and turn. Is this normal? Thanks

 

[1stGenRocks]

remember that when you try and turn the output shaft your now turning all 4 wheels so it will take more force. unless you have the tcase off or the trans out.

 

[gsxitement]

remember that when you try and turn the output shaft your now turning all 4 wheels so it will take more force. unless you have the tcase off or the trans out.

Yeah see, the tranny is out of the car still, and it's just really tough to turn. In fact I can't turn it by hand. I understand that welding everything together makes everything linked, and therefore tighter to turn, but how much turning torque shouls be present. theres practically no end play on the output shaft so, I'm thinking this is normal? any info?

 

[4pistons]

You should be able to turn it by hand. Make sure it's in nuetral. Can you use the VC to turn it? You just want to be sure nothing's bound up when you assembled it. Welding it shouldn't bind anything.

Rick - '91 GSX