3.76 Supra LSD Differential DIY -- SC430--
03-22-15, 07:05 PM
#48
Slow day today. Got the Figs Rear differential bushings in pretty easy. Installing the differential is definetly a two person job - the diff kept falling off the jack so I finally got my son to help adjust the jack while I work under the car. Got the axles connected without too much problem but ran into another challenge! The differential flange does not match the connector on the drive shaft. This might be a difference from the cars in Japan where I got the differential. So I need to use the flange from the OEM differential. I don't expect it to be easy - the shop manual says use a chisel and hammer to move the nut - didn't move. I will pick 35 mm deep socket tomorrow ... I should be able to get the nut off so hopefully I can get back on track.
Here's a picture of the Figs performance bushing kit.
Here's a picture of the Figs performance bushing kit.
03-24-15, 10:42 AM
#50
Companion shaft - Supra TT to SC430
Yesterday was a learning day. The problem I had with the bolts on the pinion ear bushings was due to the bushing metal center being upside down. The OEM bolts are tapered so Figs reams out a matching taper on the SS bushing center and marks the side that should point down.
The companion flange missmatch issue is because the Supra TT can have three different companion flanges. There is a discussion on this topic in the SC300/400 forum. They name the flanges as small or largre - the large one matches the SC430. It is not clear to me why the differential I purchased had the smaller flange - might be a difference in JDM or perhaps it came off the 6 sp manual vs 4 speed automatic which I ordered ??? Nevertheless, it is easy to inquire and check before purchasing or if necessary change it later. The smaller flange has a distance of 102mm between the bolt edges while the SC430 flange has 112mm.
I ordered the correct companion flange from LParts, our new sponsor. Price was $98.87 including $8 for 2-3 day shipping and $2.26 for a new nut.
Part no. 41204-30040 (same part no. For one of the three Supra TT choices)
Changing the flange has a couple of tricks. One is that the 35mm nut is crimped to a depression in the pinion - I bent it out using a small stanrd and phillips screwdriver and a hammer. The other trick is that a typical impact 35mm socket won't fit in the space in the flange to reach the nut; tye large hole is tapered. If you have a axle nut set, you will have to grind down the 35mm socket to fit. A thin wall deep socket should fit.
Flange replacement - another issue - the flange has a pre-load setting which is the pressure it puts on the pinion. You can count the number of exposed threads or use a digital torque meter to set it to spec when you tighten the new flange down. Remember to crimp the nut again over the depression so it doesn't move.
Here's a picture with the specs.
The companion flange missmatch issue is because the Supra TT can have three different companion flanges. There is a discussion on this topic in the SC300/400 forum. They name the flanges as small or largre - the large one matches the SC430. It is not clear to me why the differential I purchased had the smaller flange - might be a difference in JDM or perhaps it came off the 6 sp manual vs 4 speed automatic which I ordered ??? Nevertheless, it is easy to inquire and check before purchasing or if necessary change it later. The smaller flange has a distance of 102mm between the bolt edges while the SC430 flange has 112mm.
I ordered the correct companion flange from LParts, our new sponsor. Price was $98.87 including $8 for 2-3 day shipping and $2.26 for a new nut.
Part no. 41204-30040 (same part no. For one of the three Supra TT choices)
Changing the flange has a couple of tricks. One is that the 35mm nut is crimped to a depression in the pinion - I bent it out using a small stanrd and phillips screwdriver and a hammer. The other trick is that a typical impact 35mm socket won't fit in the space in the flange to reach the nut; tye large hole is tapered. If you have a axle nut set, you will have to grind down the 35mm socket to fit. A thin wall deep socket should fit.
Flange replacement - another issue - the flange has a pre-load setting which is the pressure it puts on the pinion. You can count the number of exposed threads or use a digital torque meter to set it to spec when you tighten the new flange down. Remember to crimp the nut again over the depression so it doesn't move.
Here's a picture with the specs.
03-24-15, 10:46 AM
#51
I am learning as I go - mechanic wannabe ... So I am not sure what you mean by torching the nut? I have read that as trick to help getting if off so it expands? I didn't need to do that. I have't used a torch yet but I'll get to that and learn first safely. 
03-26-15, 08:42 AM
#52
I hope you succeed in the end. For the rest of us maybe easier to just swap the internals and leave the stock gear ratio alone.To make things easier this time I purchased from Harbor Freight a 450 lbs transmission lift to support the differential. I also picked up a bench grinder and stand to be able to modify sockets and tools when necessary. I will start by grinding down the 35mm deep impact socket ... I figure some of the savings doing DIY projects can be spent on tools for the next project.
Thanks for the support. When I have everything working I'll post a summary with lessons learned.
Last edited by SlvBullet; 03-26-15 at 09:19 PM. Reason: Typos
03-26-15, 09:13 PM
#53
Good day today. The new flange came, put it in and torqued to spec. Managing the differential was soooo much easier with the transmission jack. I connected first the axles, then the drive shaft. The slowly raised the diff to the level of the rear sub-frame mounting bushings and inserted the three bolts. Last screwed in the new pinion ear bolts through the new Figs bushings. Then I went back to tighten and torque to spec all the bolts. Once the differential was in I proceeded to reinstall parts in the order they came off. Finished the drive shaft heat shield and the rear member supports. Tomorrow I'll continue with the rear chassis center support, the rear side chassis support beams, the rear sway bar and the exhaust. Then to the test drive!
Will post more details and summary tomorrow.
Will post more details and summary tomorrow.
04-02-15, 06:50 AM
#57
Lexus Test Driver
It seems like the biggest challenge with your DIY was getting the siezed bolts off as well as changing out the bushings. I hope I can get by without changing the bushings since my differential has 21k miles..
04-02-15, 10:50 PM
#58
Looks like there are three points at which you applied the PB Blaster. Since my car is a 2002, I assume these bolts are quite seized. Before I attempt the install I will shoot the lubricant all over there.
It seems like the biggest challenge with your DIY was getting the siezed bolts off as well as changing out the bushings. I hope I can get by without changing the bushings since my differential has 21k miles..
It seems like the biggest challenge with your DIY was getting the siezed bolts off as well as changing out the bushings. I hope I can get by without changing the bushings since my differential has 21k miles..
06-19-17, 11:26 PM
#59
Would love to see some Dyno numbers on this LSD, not sure if SlvBullet is still active. Heard so much awesomeness about his SC430... especially the exhaust. Anyone got a link to his exhaust build? I'm starting my "Envy" list of engine modifications (including custom exhaust, single turbo with piggyback ECU, PPE headers with O2 sim, upgraded coils and spark plugs, LSD, Torque Converter... or possibly swap to 2JZ engine and change plan of attack). In any case I would not jeopardize losing the top function or CEL lights, etc. Any thoughts or suggestions? Things I haven't thought all the way through? Maybe I have a screw loose? Manic episode? Who knows... hoping to hear from you all.
04-23-20, 04:49 PM
#60
Hi Lexiss_sc430,
Thank you for your posts. Sorry to be writing 10 years later. With respect to your car doing 65mph at 2,500RPM with the 3.76 ratio diff, what are your rear tyre dimensions e.g. 275/30/R20?
Thank you for your posts. Sorry to be writing 10 years later. With respect to your car doing 65mph at 2,500RPM with the 3.76 ratio diff, what are your rear tyre dimensions e.g. 275/30/R20?
Last edited by JMal; 04-23-20 at 08:12 PM.
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