Hi.

Hypothetically I have two identical cars with same power. Hypothetically it is 3xx rwhp. One has 4.10 SII Diff and another has 4.10 GTX LSD Diff. I know that the TII Diff is a stronger unit, however I do not know if there would be any difference in:

Straight Line Traction
Autocross Traction
Overpower powerslides (not weight transfer drifting)

I'd also love to hear what kind of diffs they are, what way etc.

Thanx!

 

need to know what years you're talking about.

GT-X != GXL, btw.

 

1990 TII and 1988 GXL***

 

1990 TII comes with a 4.1 Viscous LSD 8-inch rear end with a 5th gear of .719
1988 GXL comes with a 4.1 2-Way Clutch-type LSD 7-inch rear end with a 5th gear of .697

 

Thanks for info, I guess question still is what is the difference between 2-Way Clutch and Viscous in:


Straight Line Traction
Autocross Traction
Overpower powerslides (not weight transfer drifting)

Also I'm guessing that 1988 Auto LSD is exactly the same except with 3.90 gear?

 

Clutch is more abrupt when engaging, but definitely a harder hold, the viscous allows for a slight slip before it engages, but it does so smoothly.

Straight-line traction would favor the clutch-type hands down.
Autocross traction, depending how you set up your clutch-type, it would bite better and keep you from lighting up tires.
Overpower powerslides, the clutch-type holds better throughout.

Yup on the 3.9.

 

Appreciate the info.

Took a pic of the Diff:



Most of time one wheel spins basically. Im trying to figure out if I have open diff or broken diff... Does that supposed to say limited slip on that "tag"? Only see the word slip. I'm not sure if this rear is original with the car which is why I wasn't sure what is going on with it. Maybe previous owner has wrong fluid in it. Clutch based rears do spin because of that right?

 

That's a broken LSD.

 

Do you think it would be easier to take this thing apart or just replace the whole unit?

 

it's more mechanically intensive to remove it and open it up and replace the internals, but if you do that, you can put in a new LSD, or rebuild one. Additionally, if you have the money, you can also swap ring & pinion gears and gain acceleration at the trade off of top speed per gear.

It's obviously much easier to swap out the rear end with another rear end, but unless you know the condition of the other rear end, it's another guessing game.

 

I was thinking about a 3.90 GLX Unit since my car is a swap. I'll look into it, I've never changed internals of a diff myself.

 

3.9 gives you less acceleration with more top speed. But as a bonus, cruising at 80 mph is really gas efficient since you're in the rotary sweet spot. (between 2.5k and 3k in 5th gear)

Stock 86-88 GXL's came with 4.1 LSD

 

I guess I'll have to look for auto 86-88 GXL Diff then? I think those came with 3.90. I'm looking for more speed, less acceleration/wheelspin (haha)

 

Auto 88 GTU as well, would suffice, as would Auto 86-87 Sport's I believe.....check the stickies in this section.

You do realize that (NA gear ratios, stock tire size), your top speed based on gearing is 180 mph @ 7000 rpm in 5th gear? If you can't top that out, you don't need more speed. Speed comes from both your engine and your gears both letting you get there. You need to have both to reach a given speed.

You have a TII or NA?

 

I have a 302 swap in an N/A model that redlines at around 6250 and peaks at 5100 and torque probably peaks 3000ish...this is a auto x car/drift car

 

The lower ratio will give you wider gears and hence more traction which will make it better for the autox, but fail more at drifting. However with the torquey v8 I doubt you will have any problems powersliding.

Rofl.

 

^ Thanks for providing me with information I didn't know on my own

 

You're welcome.

 

Let me know when you want to run your 383, I'd love to rip on it with my small 302

 

Can you top out 5th gear?

 

I Could** do it but I'm done with driving that fast on public roads
This cam needs lower gearing...especially with spray.

 

Well, if you can top out 5th gear (i.e. bouncing off the rev limiter in 5th assuming you have a 5-speed tranny), then by all means, install a 3.9. Hell, install a custom R&P that's the highest number without topping out 5th gear, if you have the money. That's the ideal way of making sure your car can exert it's full horsepower if you need to.

How'd you bolt a 302 SBC to a RX-7 N trans?

 

It's a Tremec T-5 and I calculated top speed is 181 with tires that I have (245/50/16) and 4.10 gear. What is a custom R&P you're talking about?

Thx

 

How much power are you putting out to hit 181 mph?

R&P is the same as the 4.1 gear, stands for ring & pinion. Custom one would be a custom number, like 3.53 or 3.72, etc....

 

295 rwhp untuned..car probably has another 20-30 rwhp without nitrous if not more. Don't think I want to drop a lot of $ on custom R&P right now, I just need to get lucky enough to find a working used LSD with 3.90s

I've had my FD up to redline (almost) in 5th which equals 180 mph (422 rwhp), had plenty of pull left, so I know this thing can hit 18x with just 300 at the wheels