Front Differential Experts/ Gurus Needed.

[project_tsi]

Alright guys here the deal.

Wednesday I started the install of a SBR LSD insert in my 91 turbo FWD trans. Everything was going as planned until.... I remove the large gear on the stock diff which is held in by 8 19mm bolts. You remove this gear to gain access to the small pin that needs to be removed. The pin is tapered and can only be removed one way, by removing the large gear first. You remove the small pin, because its holds the large pin in place inside the diff. All the vfaqs that I read state that the small pin will be very easy to remove. A few taps and it will come out, then you can remove the large pin.

Heres where it went bad. Half, yes half of that small pin fell out of the diff. Weird, but ok. So I proceed to try and tap/ hammer out the rest of the small pin, but it won't move. Shit, it won't even budge a bit. So what now? I start to further inspect the diff and I find out that the spider gears inside the diff won't turn at all. Its like its a welded diff but its not, the gears are just froze up or some shit.

So what to do now? After some thinking time I remember that I have a 90 OR 91 (not sure, I honestly can't remember) 2.0L 5 sp Non Turbo Tranny laying around, and decide to just tear into the trans and remove the diff to use in my trans. Hopefully the diffs are the same.

That step went like butter. I removed the NT diff easily, the gears inside spun freely like they should and the small pin came out easily as well. So great. I have a good front diff to use now, Right? Thats where I'm stuck at now.

I decided to do some comparison work on the 2 diffs. The diffs are alike, but they are also very different. In my pics, the turbo 91 diff is on the left, and the NT diff is on the right, it also looks alot cleaner than the turbo diff.

One thing I noticed is that the turbo diff has 20 roller bearings inside the 2 bearing housings. The non turbo diff has only 17 roller bearings inside the bearings housings. I sat the NT diff in side my turbo trans and it spun freely, but I am unsure of if it will successfully work or not in the turbo trans. Any one know if this is turbo/non turbo specific or 90/91 specific for roller bearing amount?

Another I noted is that the turbo diff physically looks a bit "beefier" than the NT diff. The actuall diff casted housing seems to "cup" a small bit more around the open gear window than the NT diff does. I don't know if this is a stregth issue or what, someone know? Also one 4 of the 8 threaded holes on the turbo diff, that hold on the large gear, they have a raised backing, which looks like it allows for more threads and possibly more stregth? Not sure on that either.

Also they have different number stampings in different areas of each diff. The NT diff has 10 and a C0 I think on it, its located adjecent to the window cutouts on the sides of the diff housing. The turbo diff has B9 and 6C on the top of the diff about where the large ring will bolt too.

So, anyone have some helping info for me? Will the NT diff properly work in the turbo trans? Is the NT diff any weaker than the turbo diff? Does the roller bearing amount matter? This is really holding me back as I am very close to dropping the engine back in the car soon, and frankly I don't have the money to replace the diff with a Quaife or a Kaaz or else I would have.

Remember, for the pics, Turbo on Left, Non Turbo on Right.

Thanks for any help that you can give, and I always give out rep pts for helpfull info.

 

[project_tsi]

A few more pics.

 

[99gst_racer]

A few more pics.

As if we needed any more pics!
**Re-titles thread "Official Differential Picture Thread**

Just Kidding.


If I were you, I would have 2 options:

#1) Weld the gears on the turbo diff. and sell the LSD insert (and use the $ toward those new CV shafts)

#2) We can take it down to PME and press that pin out. Then use the pin from the N/T diff.

I personally wouldn't take the chance using the N/T diff. You will be making alot of torque this year, and it would be a shame to gernade that thing. They do look dissimilar enough for me to not want to take the chance. Just my mangled .02. (get it?)

 

[GTM]

A few more pics.

Yikes, got a can of worms there.

First you need to be using a brass punch. I see just the thing I mentioned elsewhere when someone used a ball peen hammer on a large tractor track bearing. On the side near the satellite gear pin someone has used a sharp punch and dimpled the carrier. You will note the discoloration on the pin near the the punch mark. You just can't be banging on case hardened percision machined parts with steel tools. It wouldn't surprise me if this is why it's broken and frozen. Your local good hardware store may have 1/2" brass rod stock, buy a couple of feet so you can cut to length. 3", 4", 6" lengths are probably the most useful for driving bearings and pins out etc. The remaining you can grind a taper / point for limited access.

I can read one of the bearing sizes, you can probably plug it / them into a Google search to see availability, exact size, and interchange if needed.

Since you probably don't have a surface plate you can buy a cheap substitute a 3/8"-1/2" piece of plate glass which is quite accurate for being flat... .001". This is where you need that straight edge. Again your hardware store may have 1/4"x2" aluminum bar stock you need a 2' section, I'm sure Home Depot will have these if the hardware doesn't.

You need to measure the heights of all the critical machined parts. BTW I saw a small nick on the edge where the ring gear mounts. This needs to be filed down so the ring gear will not bridge up when mounted. If you don't do this your setup will be screwed for the gear will not accurately mesh with the pinion gear. You can take rubbing compound or Ajax and smear it on the face to lap the gear onto the carrier. This will show all the high spots where you will need to inspec for proper seat. If you need to check diameters of large parts such as this, Harbor Freight has a 12" vernier caliper with dial for around $25 I think.

Back to the problem, try the 3' brass drift and the largest hammer you can swing comfortably. Set the carrier on plywood and a block of wood to support the exit side of the satellite pin and hit it as hard as you can. If you have to use ViceGrips to hold the brass drift don't be shy it will save some bone bruises should you miss. If this fails then you need an acetylene torch to heat the carrier up to the smoking point all over. If it catches on fire throw a rag over it for a couple seconds and keep heating. Why smoking, because the oil will all burn off just around 500 degrees F. so keeping it below this temp will not change the metal properties but will expand the hole and then use your drift. If you don't have a torch then you will need to go to a muffler shop and have them heat it while you do the hammering.
.............

You may be able to use the other carier and just move your parts except for the satellite and planetary gears. For goodness sake check the spline on the axles and the new gears, otherwise you are screwed. At this point I will say you are going to have the better part of a day in this aspect of your install. Of course you realize that if you are mixing and matching parts you will have to set up the diff preload. You will need some Prussian Blue for checking gear mesh patterns. If you can't find this then some white Lithium grease can work.

This is just a short reply for if you have never set up a Diff you are in for a treat.

Any questions????

Cheers,
GTM

 

[GTM]

...
#1) Weld the gears on the turbo diff. and sell the LSD insert (and use the $ toward those new CV shafts)

#2) We can take it down to PME and press that pin out. Then use the pin from the N/T diff.

I personally wouldn't take the chance using the N/T diff. You will be making alot of torque this year, and it would be a shame to gernade that thing. They do look dissimilar enough for me to not want to take the chance. Just my mangled .02. (get it?)

I'm not sure if you are kidding about welding the planetary and satellite gears. He will loose his differential which then puts a lot of strain on assembly, the axles, wheel bearings and tire wear. Parking will be a real chore and forget ever having to push it around except in a straight line. I've pushed enough formula cars around with limited slip and they weigh 1/2 what what this does.

If someone has access to a parts catalog they may be able to show if the carrier is the same and only some of the parts are different including the bearings.
..................

If you have access to a press then by all means this will be the best method if a few more hits with a brass drift don't get it out. You stil may have to heat it since it's obviously taken a beating.

Cheers,
GTM

 

[loweperf]

According to Alldata.
91 Laser FWD Turbo calls for differential case MD734846
90 and 91 Laser FWD non-turbo calls for MD719462
so they are different

 

[GTM]

According to Alldata.
91 Laser FWD Turbo calls for differential case MD734846
90 and 91 Laser FWD non-turbo calls for MD719462
so they are different

Actually the parts to compare are the carrier (part which holds the ring gear, satellite and planetary gears). Not the aluminum casting/housing if I understand your reply correctly.

Cheers,
GTM

 

[loweperf]

These should be the right numbers. Thats just the way they list them in the parts catalog.

 

[GTM]

These should be the right numbers. Thats just the way they list them in the parts catalog.

Thanks for confirming that. Are the satellite, planetary gears, and pin the same numbers?

If not he's in a world of hurt. He might just be lucky and it's the broken pin that has them jambed together but you know they were spinning when under pressure. The gears don't look to be in bad shape so can only guess that previous repair was done poorly or dropping a spinning wheel down on a curb. More common is to see twisted axles though I have seen a few broken pins, gears and even a carrier which was sidways in the housing.

Cheers,
GTM

 

[project_tsi]

or dropping a spinning wheel down on a curb.

Hmm. Yeah, thats it. Its gotta be that. Very late last season, actually 2 days before I put the car up for storage, my buddies talked me into doing one last massive burnout. Of course it was a one wheel wonder, and I always had that in the back of my mind that that was the culprit.

Well thanks for the help so far guys. I think first my best bet is to try and get that small pin pressed out, or I'll do as you said and use the torch method. Hopefully once the pin is out the gears will free up. If they do I will just use the other small pin from the nt diff and put it back together using my turbo diff. God I hope its as easy as that. If it is, then for sure, no more 1 legger peggers for me.

Thanks for the help again.

 

[loweperf]

Are the satellite, planetary gears, and pin the same numbers?

They are not the same
Turbo
Gear Set MD722129
Shaft MB185334
Non Turbo
Gear Set MD722127
Shaft MB092834

 

[GTM]

Hmm. Yeah, thats it.
...
my buddies talked me into doing one last massive burnout. Of course it was a one wheel wonder, and I always had that in the back of my mind that that was the culprit.

Well thanks for the help so far guys. I think first my best bet is to try and get that small pin pressed out,
...
for sure, no more 1 legger peggers for me.
Thanks for the help again.

Oh no, were your buddies so impressed they offered to help with the repair expense. That 'll learn ya the hard way.

I'm now confused about which pin, I thought you were talking about the gear shaft. The only other pin I saw was a locater for the ring gear, was there another? Which pict?

I'm hoping the carrier wasn't distorted if it's not the shaft that's giving problems something is causing them to bind. Again with a brass drift you could try to free the planetary gears, if you have something binding there it could spell doom and gloom. I've lapped these gears before using valve grinding compound if things aren't wasted.

It's always the dumb things that get you into trouble every time and get costly.

Cheers,
GTM

 

[project_tsi]

Let me try and explain a little better.

Lets say you remove the entire stock front diff. Then you remove the very large gear that is bolted to the diff. The gear is held in by 8 19mm bolts. They almost look like flywheel bolts, but bigger. I will include a pic of me removing the 8 bolts, followed by the gear.

The reason you need to remove this gear is because there is a small tapered roll pin that can only be removed by removing the large gear, b/c its tapered, it only goes in and out the one way, when the gear is on, it acts as a wall so the pin cannot back itself out. This small tapered pin is there to hold the larger pin in place. The larger pin being the pin that inside the diff housing and it connected to one set of the gears, I'm not sure if its the sattelite or planetary gears as I'm not a diff/ gear guru, but its one of them.

Once the small pin is out, then you can remove the larger pin, and install the lds insert device, and then reinstall the large pin, followed by the small pin, and large gear, and finish re assembling the tranny.

And I also agree with you that if enough force was applied to the gears inside the housing, that they would spin, like if it were installed in the car.

So I hope this cleared things up for you.

 

[project_tsi]

Here is a pic of the small tapered roll pin in which I was reffering too.

 

[GTM]

Let me try and explain a little better.

So I hope this cleared things up for you.

Now I understand though not found it yet.

In you pict #9 I see some crud coming out of the gear and the shaft on the left side. Are these metal particles??? Lie to me, tell me they are not...

Cheers,
GTM

 

[project_tsi]

I looked closely into the particles and they appear to not be metal. Both diffs that I took the gear off of had some of this "crud". I believe its just some threadlocker that was applied to the bolts, as none of it was metal like and it all dissinigrated in my hands when I rubbed it.

But what I don't get is if the small pin broke, then why did it lock up the gears? Any ideas on that?

Perhaps I should take the diff over to TRE, they are about 45min from me.

 

[GTM]

I looked closely into the particles and they appear to not be metal.
...
But what I don't get is if the small pin broke, then why did it lock up the gears? Any ideas on that?

Perhaps I should take the diff over to TRE, they are about 45min from me.

That's good if not metal could chk with magnet.

Just guessing here:
I'm thinking the pin is secondary to the event. If you look at #9 and pretend the bottom gear which has the spline for the axle is held rigid and cannot rotate. Now the opposite gear is spinning with max Hp with the planetary / satellite gears doing a full differential which may be twice the speed(?). It now suddenly grabs, every bit of torque/hp/load is transmitted through those beveled gears and the shaft which now want's to explode as the forces want to make it longer along the splined axles and the shaft gears will squeeze together. If the loop portion of the casting racks then the shaft will be under pressure and then broke the pin.

As I mentioned I've seen Diffs explode to where the case breaks at the bearing outer bearing race, axles shear off and the carrier drop down inside the housing.

I would suggest you have someone look at it in real life, I can't get a gut feeling for it from just looking at pictures. If it did what I said you may have to shim the side bearings if it distorted the housing, then correct for this by shimming the pinion gear.

I keep coming up with thoughts that bother me and I don't want to paint a glossy picture for this could be seriously hurt. I do find it interesting that if it had a lock pin for the shaft then why the need for Locktight which is going to keep the shaft from moving unless you cook the heck out of it.

Cheers,
GTM

 

[project_tsi]

Would it be possible if some of the gear teeth broke off and caused it freeze up, and its just out of sight right now? I didn't see any shavings/ teeth inside the trans at all and there is no damage to the casing that usually results from broken teeth but I'm just throwing this out there.

 

[GTM]

Would it be possible if some of the gear teeth broke off and caused it freeze up, and its just out of sight right now? I didn't see any shavings/ teeth inside the trans at all and there is no damage to the casing that usually results from broken teeth but I'm just throwing this out there.

Yes it's possible; however; nothing was seen. Unlike the ring and pinion which are designed to not repeat same tooth contact say for every 4 or 11 revolutions (can't remember which on a 4:11) these are direct relative. I still see no evidence of this for when they start to break pieces will lodge in the tooth gullet and scar it as the tooth forces it into the v. There are no radical scratches or wear marks on any of the teeth including the ring gear for that was the first thing I was looking for. I blew the picts up to full screen on my 21" monitor which made it at least twice normal size and how I was able to spot the nick on the carrier face.

You could just try prying with a flat blade screwdriver and see how hard they are to move. It's entirely possible that you got a piece of gasket lodged in the teeth and we are worrying about nothing. If you have a large bench vise you can line the jaws with card board and clamp the diff and then insert an axle into the spline and see if you can turn it with a pipe wrench. It's possible you made one of the gears egg shape so it will come up hard every 1/2 revolution. Try some of these things and we can discuss the findings.

Too bad you didn't get into this earlier in the week so you are not stuck over the weekend. Do these things exist for $50-$75 from wrecking yards, you might be better off rather than whipping a dead horse for the amount of time involved.

Cheers,
GTM

 

[Ryan95tsiAWD]

We just bought the insert for our FWD and after seeing his problems, I am curious if I can use our spare AWD front diff in the FWD tranny. That way I can have half the work done before we even tear into the car and if we have a problem the car is not down for however long it takes to fix this.

So, are the FWD and AWD front diffs interchangeable?

Thanks,

 

[GTM]

We just bought the insert for our FWD and after seeing his problems, I am curious if I can use our spare AWD front diff in the FWD tranny. That way I can have half the work done before we even tear into the car and if we have a problem the car is not down for however long it takes to fix this.

So, are the FWD and AWD front diffs interchangeable?

Thanks,

I am not a DSM specialist so hopefully someone else can give the correct answer. I didn't want you to think your question was being ignored.

My limited experience with AWD suggests they are not, in some vehicles they even use a different gear ratio and specify for off road only so the tires can slip in the dirt.

Anyone else know the answer???

Cheers,
GTM

 

[99gst_racer]

I'm not sure if you are kidding about welding the planetary and satellite gears. He will loose his differential which then puts a lot of strain on assembly, the axles, wheel bearings and tire wear. Parking will be a real chore and forget ever having to push it around except in a straight line. I've pushed enough formula cars around with limited slip and they weigh 1/2 what what this does.

I was under the mistaken impression that Dan was making this a track car, not a daily driver (with the whole new motor and all).

 

[mavisky]

I was under the mistaken impression that Dan was making this a track car, not a daily driver (with the whole new motor and all).

Even then it'd be a bi*** to be in the near lane at the drag strip and not be able to make the turn onto your lane

I actually had the same problem with my diff when I went to install the phantom grip upgraded spring assembly, but I had another diff. I never even bothered to look further into the problem.

 

[Ryan95tsiAWD]

I am not a DSM specialist so hopefully someone else can give the correct answer. I didn't want you to think your question was being ignored.

My limited experience with AWD suggests they are not, in some vehicles they even use a different gear ratio and specify for off road only so the tires can slip in the dirt.

Anyone else know the answer???

Cheers,
GTM

Thanks for the quick reply

I thought this would have been another one of those "over addressed" topics on here, but have yet to find any info that would validate either way.

I have a 97 AWD Front diff with "2204" stamped on one side and "8" on the other side.

I also have a 95 AWD front diff, but I would have to finish pulling the tranny from the car/tear it down. I am not feeling that motivated considering we have to replace the crank in the GST next weekend. I imagine they are the same AWD front diffs in either case.

 

[project_tsi]

Well guys, its looking like a glim future for my stock diff. Today I took the diff over to a friends house. He has machinists tools galore. We did everything we could trying to get that small pin out. We even used a 3 ton press, and it did not budge. So finally, we set up the diff on his drill press and sucessfully drilled out the small pin and removed, not damaging the housing or large pin one bit.

So now the small pin is finally out so we move on to the large pin. Won't budge. Shit. Tried a few whacks with the ol sledge and a brass pin. No budging. Then, we try the 3 ton press, won't budge. He's got one more press, a 50 ton hydraulic, yeap, won't budge. Wow, not even trying to move. I tried using a flat head screwdriver and then a small crowbar to get the gears to turn at all, and no luck their either. Nothing will move.

The only other thing to try now is heating it up, but then that runs the risk of making the gears/pin brittle or anneald if its heated up or cooled down to fast. Even then if we manage to remove the pin, there will most likely be some kind of damage which would require the gears and pin to be replaced, along with the shims, and then bearings while I'm at it, and god knows how much those gears and pin are going to cost. Then if you factor in that there runs a good chance of the stock diff grenading 2 months down the road from the high 2.3L torque the car will have this year, its almost a better idea to save my pennies and wait till I can afford a Quaife style diff. If the stock diff were to go after I put a few hundred in rebuilding this stock diff, there runs a high chance of it taking the better part of the entire trans with it. So its either save my pennies now, and spend $800 on a new true ATB Diff, or spend $2-300 on getting the stock diff repaired/replaced and then another $2k later on when the trans explodes when the diff does. Hmm. Looks like the car's going to be sitting a bit longer then anticipated, again.