Supra/Celica Differentials - Please Educate!

So the 1983 Celica I picked up recently has a rear subframe from a Celica/Supra of similar vintage, meaning that it's equipped with a semi-trailing arm setup instead of a live axle.

I have two differentials for the thing that reputedly were both LSD-equipped. However, when locking the input shaft and spinning one output, the opposing shaft rotates in the other direction. I believe this indicates that the LSD is no longer functioning in either diff.

What I'd like to do is continue to run with the differential that's currently in the car, and rebuild my spare in the mean time. I've attached (or tried to attach) a couple of photos below. The thing doesn't seem to have any tags on it, except for a '3' on the rear cover. I'd say the ratio is a little over 4.0:1 based on spinning it by hand.

Can anyone help me identify the diff? Are these clutch type differentials? Do we know of any resources to rebuild these things? Are these the same diffs you guys seem to love for Merkur builds?

Photos: http://imgur.com/a/T2Bvp

Thanks!

Jay, this:


Is Toiletta 7.5" diff..

This:


is the Toiletta 8" Supra MkIII aka MA70 diff and the Ford 7.5 diff it replaces.

You and see the mounting is different and the output flanges are bigger 6 bolt thangs..

Inside your diff there are a whole bunch of little coil springs setting up the pre-load, inside the Stuprah is ONE BIG HERKI spring

You're probably just going to have to open it up and see what you have and search a bit for set up info...
here's what local randy's ring and pinion says:

Quote

Toyota 7.5" Rear
Toyota 7.5" Rear Differential

Ring Gear Diameter: 7.500
Cover Bolts: 10
Ring Gear Bolts: 10
Spline Count: 27
Dropout: True
Pinion Support: False
Carrier Breaks: none
Rear Suspension: Solid
Pinion Nut Size:


Compatible with Models:

Hilux Pickup: 1979 - 1997 (Rear) Pickup: 1977 - 1995 (Rear)
Tacoma: 1995 - 2006 (Rear)

That's the solid axle stuff but the guts are the same..

Going to swap final drive? That thing would go like stink with a 4.88.

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

The Supra 7.5" LSD is just ok. http://www.weirperformance.com/home.html makes a rebuild kit for them that increase the clamping force by a considerable amount, like double or triple the factory amount. It's likely a 4.1:1 ratio, most of the Supras of that era were. It's very easy to take the back diff cover off and make sure it's an LSD, which is what I would do before buying a rebuild kit. Also, consider using the factory plates rather than the ones that come in the kit, they are a bit more grippy.

-Jon

Quote
RDR
So the 1983 Celica I picked up recently has a rear subframe from a Celica/Supra of similar vintage, meaning that it's equipped with a semi-trailing arm setup instead of a live axle.

I have two differentials for the thing that reputedly were both LSD-equipped. However, when locking the input shaft and spinning one output, the opposing shaft rotates in the other direction. I believe this indicates that the LSD is no longer functioning in either diff.

What I'd like to do is continue to run with the differential that's currently in the car, and rebuild my spare in the mean time. I've attached (or tried to attach) a couple of photos below. The thing doesn't seem to have any tags on it, except for a '3' on the rear cover. I'd say the ratio is a little over 4.0:1 based on spinning it by hand.

Can anyone help me identify the diff? Are these clutch type differentials? Do we know of any resources to rebuild these things? Are these the same diffs you guys seem to love for Merkur builds?

Photos: http://imgur.com/a/T2Bvp

Thanks!

Look for a plate on the firewall that contains information about the vehicle. The differential section should have a 4 alphanumeric code. For example: F293, F=7.5" ring gear, 29=4.1 ratio, and 3=2 pinion LSD. Google for Toyota axle codes.
http://www.toysport.com/technical%20information/toyota%20differentials%20identifications.htm

---

www.performanceoptions.net

Quote
noypiesky
Look for a plate on the firewall that contains information about the vehicle. The differential section should have a 4 alphanumeric code. For example: F293, F=7.5" ring gear, 29=4.1 ratio, and 3=2 pinion LSD. Google for Toyota axle codes.
http://www.toysport.com/technical%20information/toyota%20differentials%20identifications.htm

The problem with that, is that the Supra rear subframe/diff (7.5" ring gear) is a popular direct bolt in swap on the <'85 GTS Celicas. The GTS independent rear came with a 6.7" ring gear up to '84, in '85 they used the 7.5"

I dont remember years, but my STRAIGHT AXLE 7.5" celica supra diff is LSD.... because it came from canada. I don't believe we got LSD STRAIGHT AXLE diffs here.

So, if its from the straight axle car, if its US, its probably open.


EDIT:

Just reread, you said its got the semi trailing arm, not the live axle, disregard this post.

---

Welcome to the cult of JVL drink the koolaid or be banned.



Edited 1 time(s). Last edit at 08/19/2013 02:02PM by Dazed_Driver.

Thanks a ton for all the info guys, especially the link to the rebuild kits! I'll open the diff and see what I'm working with. I don't think a shorter ratio is in the works at this point, but I'd love to have a nice tight LSD in the back.

Unfortunately I've never rebuilt a differential before. I understand that a couple of special tools might be required to set pinion lash and similar. It appears as though Weir performance had planned (as of 2009) to create a writeup regarding the installation process. I'll talk to them and see if I can get my hands on some decent information - at least enough to decide whether to risk tackling this myself!

Quote
john vanlandingham
Going to swap final drive? That thing would go like stink with a 4.88.

Even with that big 2.7 or whatever engine, better gears = more awesome.

---

Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.

Actually, Weir seems to offer some cool ring and pinion kits for not a ridiculous amount of money.

Choices include 4.56, 4.88, 5.29, and 5.71:1 ratios. I wonder how short is too short. I guess I'll have to do some trans research and figure out the available speed ranges.

Quote
RDR
Actually, Weir seems to offer some cool ring and pinion kits for not a ridiculous amount of money.

Choices include 4.56, 4.88, 5.29, and 5.71:1 ratios. I wonder how short is too short. I guess I'll have to do some trans research and figure out the available speed ranges.

You know, there are some here who have been doing this modding gearing stuff for like 45 years...
You could have a dialog with them and probably get a better answer sooner that researching on your own. (since in North America among those that write for magazines/fanzines/"the web" generally are among the most ignorant people not under restrained medical care, and thus unlikely to consider/ask/discuss gearing---since its not shiny.)

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Or really cheap, most all of the Toyota vans, with the 7.5" axles, came with 4.30:1, if you needed just a little more gearing advantage. Not really important to this post, but it's possible (Weir sells a kit) for installing the Supra 7.5" LSD into the live axles. That's how I set up my live axle Celica.

-Jon

Quote
jrally
Or really cheap, most all of the Toyota vans, with the 7.5" axles, came with 4.30:1, if you needed just a little more gearing advantage. Not really important to this post, but it's possible (Weir sells a kit) for installing the Supra 7.5" LSD into the live axles. That's how I set up my live axle Celica.

-Jon

Yeah that's a good point...if that motor is some herking big monster that doesn't rev anything them that damn 4.3 sounds real good...
Really odd but 2 very useful gears are often NOT in the inventory of Toyota's gears in the Aftermarket: 4.3 and 5.1

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Quote
john vanlandingham

Quote
RDR
Actually, Weir seems to offer some cool ring and pinion kits for not a ridiculous amount of money.

Choices include 4.56, 4.88, 5.29, and 5.71:1 ratios. I wonder how short is too short. I guess I'll have to do some trans research and figure out the available speed ranges.

You know, there are some here who have been doing this modding gearing stuff for like 45 years...
You could have a dialog with them and probably get a better answer sooner that researching on your own. (since in North America among those that write for magazines/fanzines/"the web" generally are among the most ignorant people not under restrained medical care, and thus unlikely to consider/ask/discuss gearing---since its not shiny.)

A fair point; that's why I'm here - to learn from other's experience, and maybe someday if I'm lucky, be able to contribute something!

So let me be more direct. It seems like there are several choices for much shorter ratios than what I have (which I believe is about 4.1:1). The car is responsive, but the Tacoma truck engine (3RZ-FE) only revs to about 5500-6000 rpm. It has a nice fat torque curve, which is good, but I could certainly take advantage of a greater multiplier.

How short is too short? If I were to do this, should I go as low as possible and grab the 5.71 set? The car has the stock 83 Celica GT-S trans. Any guidance is welcome and appreciated.

Quote
RDR

Quote
john vanlandingham

Quote
RDR
Actually, Weir seems to offer some cool ring and pinion kits for not a ridiculous amount of money.

Choices include 4.56, 4.88, 5.29, and 5.71:1 ratios. I wonder how short is too short. I guess I'll have to do some trans research and figure out the available speed ranges.

You know, there are some here who have been doing this modding gearing stuff for like 45 years...
You could have a dialog with them and probably get a better answer sooner that researching on your own. (since in North America among those that write for magazines/fanzines/"the web" generally are among the most ignorant people not under restrained medical care, and thus unlikely to consider/ask/discuss gearing---since its not shiny.)

A fair point; that's why I'm here - to learn from other's experience, and maybe someday if I'm lucky, be able to contribute something!

So let me be more direct. It seems like there are several choices for much shorter ratios than what I have (which I believe is about 4.1:1). The car is responsive, but the Tacoma truck engine (3RZ-FE) only revs to about 5500-6000 rpm. It has a nice fat torque curve, which is good, but I could certainly take advantage of a greater multiplier.

How short is too short? If I were to do this, should I go as low as possible and grab the 5.71 set? The car has the stock 83 Celica GT-S trans. Any guidance is welcome and appreciated.

OK as far as I can see the trans is a W58:

Quote

The W58 is sometimes designated as a "close-ratio transmission"; however, in its stock form it does not meet all the criteria for a close-ratio box.

Toyota engineers have shown favor to the W58 over the rest of the 'W' series by including it in so many models and even building a stronger version for higher powered applications.

Ratios:

First Gear: 3.285:1
Second Gear: 1.894:1
Third Gear: 1.275:1
Fourth Gear: 1.00:1
Fifth Gear: 0.783:1
Reverse: -3.768:1

That is remarkable similar to the Ford Type 9 that came in US market Xratties and V6 versions elsewhere:


Which means we know we can't really go much shorter than 4.3 before 1st gear becomes so short that its useless (you dig holes on starts and go down rather than forward---and the car goes 1-2 car lengths before first is revved out---not a good way to start..

But that means 5th is useless except as a gear for transits because it would be overall about 3.35---very leisurely cruising indeed..

What tire/wheel package you thinking of?

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Looking at available tire options, I'm thinking about a 185/70-14, partially because I have two sets of stock 14" wheels for the car. I don't know how strong they are, but even in the worst case I could probably at least get through one set of tires before I bent/broke too many of the things... They might be a little wide but I'd love to avoid buying wheels at this point.

This is the style, if anybody knows anything about their relative strength.

http://upload.wikimedia.org/wikipedia/commons/3/3c/Celica_GTS_1983.jpg

Alternatively, I have one set of five 15" wheels. For those I would probably end up with a 195/65-15.