Jump to content
The mkiv Supra Owners Club

Big case diff B03B broken


Gpro

Recommended Posts

Hi guys,

 

It looks like I broke my B03B (6spd) diff yesterday at standstill whilst dumping the clutch at high RPM. It's making weird noises and the car won't drive (just a tiny bit on even ground). Before I go out and buy a new LSD, does anyone know of any common issues with the big case diffs?

 

Additionally, I found a stock LSD torsen 8.7" replacement for £500. Does anyone know if I can get an upgraded one for under £1,000?

Link to comment
Share on other sites

Hi guys,

 

It looks like I broke my B03B (6spd) diff yesterday at standstill whilst dumping the clutch at high RPM. It's making weird noises and the car won't drive (just a tiny bit on even ground). Before I go out and buy a new LSD, does anyone know of any common issues with the big case diffs?

 

Additionally, I found a stock LSD torsen 8.7" replacement for £500. Does anyone know if I can get an upgraded one for under £1,000?

 

 

The commonest reason for differential or crown wheel and pinion failure is dumping the clutch at high RPM. You are in good company ;)

Link to comment
Share on other sites

The commonest reason for differential or crown wheel and pinion failure is dumping the clutch at high RPM. You are in good company ;)

 

Presumably it will be the crown wheel and/ or pinion that has been damaged? In which case, an aftermarket diff (internal) won't contain the parts needed to fix it.

Link to comment
Share on other sites

I've had my big case diff b03b took off cause it was making a lot of noise, after closer inspection the pinion wheel has lost some teeth. So now sitting on my garage floor waiting to be fixed one day.

Link to comment
Share on other sites

hmm, I guess I will wait until I get the diff off and take a look at what's wrong before buying anything. I hope it won't cost more than a grand to fix.

 

I work as an engineer building gear boxes and diffs for f1, rally and touring etc, let me now what you need if I can help I will mate.

Link to comment
Share on other sites

My diff locked up a week before xmas and all my parts are on order. Hi have been stressed to the eyeballs with it as my pinion was damaged in the process. The Jspec pinion is discontinued so I have had to order a US spec one, still £750 from Amayama. Also an Os Giken is ordered and a new prop shaft as that snapped in the process. Skint is not the word...

 

I will be making a post with the pics of the damage and rebuild once completed.

Link to comment
Share on other sites

I work as an engineer building gear boxes and diffs for f1, rally and touring etc, let me now what you need if I can help I will mate.

 

Thanks mate, I will hopefully get the diff of on the weekend and post images of the damage.

Link to comment
Share on other sites

  • 1 month later...
Something has pushed the crown wheel sideways with HUGE force, probably a tooth or three off the crown wheel or the pinion. CWP scrap, case needs bead blasting and crack testing, quite possibly it's scrap too :(

 

Drag race start?

 

Yeah it was a high rpm launch that broke it.

 

Quick question, I have a spare NA small open diff. Could I just buy a cusco LSD and put it in, or does it have to be an LSD diff to replace the torsen with a cusco one? (I understand my gear ratios will be significantly different).

Link to comment
Share on other sites

The only LSD you should consider fitting is OS Giken or if you are lucky to find one TRD but since the latter is discontinued expect to pay stupid prices for one. You could fit the small case with an aftermarket LSD and change the ratio but if you give it the same abuse as you have given this one I wouldn't expect it to last.

Link to comment
Share on other sites

The only LSD you should consider fitting is OS Giken or if you are lucky to find one TRD but since the latter is discontinued expect to pay stupid prices for one. You could fit the small case with an aftermarket LSD and change the ratio but if you give it the same abuse as you have given this one I wouldn't expect it to last.

 

I'm not planning on doing anymore launches so it should technically last, I hope!.

How would I go about changing the final gear ratio? Can't find anything online on it or where to purchase different gears.

Link to comment
Share on other sites

I'm not planning on doing anymore launches so it should technically last, I hope!.

How would I go about changing the final gear ratio? Can't find anything online on it or where to purchase different gears.

 

You would need to order the parts from Toyota, you want a 3.266:1 ratio for a small case which is part number 41201-19645. Expect the price to be eye watering or look for someone selling an A03B diff then you would have the OEM LSD and correct ratio for a manual car.

Link to comment
Share on other sites

Yeah it was a high rpm launch that broke it.

 

Quick question, I have a spare NA small open diff. Could I just buy a cusco LSD and put it in, or does it have to be an LSD diff to replace the torsen with a cusco one? (I understand my gear ratios will be significantly different).

 

You'd be best sourcing a 98- ls400 3.2 diff, small case but with a 3.2 ratio which is much nearer to the tt6 ratio than the n.a. supra ones.

Link to comment
Share on other sites

There are 2 sizes of crown wheel.large and small, and two sizes of aftermarket LSD's, large and small. Match the sizes and you should be OK. Cusco LSD's are quite horrible, grabby, juddery and unkind to the transmission and civilised driving however. TRD or Giken are far better.

 

I wouldn't mind getting the OS Giken LSD, but can't justify buying that for my spare small diff (NA open) which has the wrong gear ratios. Will try take out my current diff to assest the damage. I fit's a write off, I will be on a look out for a TT6 small LSD diff.

Link to comment
Share on other sites

Got the diff off today and upon a quick inspection it doesn't seem to look that bad. Everything seems to be in mint condition. I believe the axle stud has failed. I haven't been able to remove this, I'm presumming I need a puller? I'm hoping that's all that needs replacing. See pics below.

lsd1.jpg

lsd2.jpg

Link to comment
Share on other sites

Pull the axles stubs out. They are pressed out by threading the axle bolts through the axle stubs into the diff case. Be carefull and thread them a little at a time in order to push them out straight.

 

Remove the 8 bolts on each side around where the axle stubs were fitted. After the bolts are out gently pry the differential carriers, start with the passenger side carrier so the LSD will not fall out. Again, be carefull to pull them out straight. There is an o-ring seal around these.

 

Support the LSD with your hand and pry the drivers side carrier out.

Link to comment
Share on other sites

Pull the axles stubs out. They are pressed out by threading the axle bolts through the axle stubs into the diff case. Be carefull and thread them a little at a time in order to push them out straight.

 

Remove the 8 bolts on each side around where the axle stubs were fitted. After the bolts are out gently pry the differential carriers, start with the passenger side carrier so the LSD will not fall out. Again, be carefull to pull them out straight. There is an o-ring seal around these.

 

Support the LSD with your hand and pry the drivers side carrier out.

 

When you say pull the axle stubs out, do you mean by hand? Yes I've taken the 8 bolts our and can see the o-ring seal.

Link to comment
Share on other sites

When you say pull the axle stubs out, do you mean by hand? Yes I've taken the 8 bolts our and can see the o-ring seal.

 

They are pressed out by threading the axle bolts through the axle stubs into the diff case. Can you pop up some pictures of the side of the diff so we can see what you have done so far.

Link to comment
Share on other sites

Managed to get it all apart today. Not sure how I managed to do this, but the LSD is snapped in half, also when I drained the oil, it wasn't 1.8+ litres so i'm presumming I was running low.

 

Everything else looks fine, so I'm hoping all I need is just a new LSD and I'm back on the road!

Screen Shot 2017-03-25 at 12.43.53.jpg

Screen Shot 2017-03-25 at 12.43.41.jpg

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. You might also be interested in our Guidelines, Privacy Policy and Terms of Use.