So my car was auto w/ 3.9 LSD diff. Now i did a manual swap and have a open diff, and since ive gotten the diff ive noticed its weird behavior. For the most part i dont notice it too much when im driving but in certain gears if i let go of the gas the car decelerates, i feel like a bucking motion and sounds like its "popping".

Dont know how to explain it makes a big noise and the car jerkss around.

WEll im geting another rx7 and its a 86 gxl with 4.1 lsd, IM going to be throwing that into my car to get teh lsd diff and to see if this problem goes away. What do you guys think.

Also , do i have to also change my axles. Open diff to lsd diff axles? Or the na axles are all teh same. Cuase one of my axles is leaking some **** lol

Jason NYC

 

My car was a 1990 gxl auto, now has s4 jspec t2. I got the mazdatrix custom driveshaft. and when i decel from about 2500 and lower, it does the same buck/pop noise, i have no idea what it is, i thought the pop was coming from the exhuast. weird.

 

sure the diff is mounted right, and mounts not broken??
the bucking and popping sorta sounds like the TPS is bad lol

 

^ my tps is bad too...haha

 

TPS? Really

It really feels mechanical, like the diff is jiggling around. I gues ima check and see how its mounted or if any mounts are broken.

Whats so wrong with using a 3.9 lsd?

Jason NYC

 

Are you just releasing the gas or are you pressing in the clutch when decelerating? You might be receiving the bucking from the back pressure of the engine.

There is no difference between the axles in lsd vs open. The only difference lies with NA and T2 differentials because of the size of the pumpkins. T2 has a larger pumpkin.

 

off topic but...can i use a s5 Gtus LSD in my s5 Gxl?

 

Well i do have a massive exhaust leak my left canister is missing and its causing me to have high RPMS and shift faster.

ANd i am not holding the clutch i just let go of the gas and after is starts slowing down on its own it gets worse

EDIT; WEll im getting a s4 4.1 LSD diff tomorow and ima throw that in and see what happens.



Jason NYC

 

The S4 GXL came with a clutch type LSD. I'd think the S5 GXL would come with a LSD also which more than likely a viscous type. The GTUs was pretty much a full turbo car without the turbo engine. So I don't think you can use the GTUs differential because its a t2 diff with viscous LSD. Like I said before the NA and T2 diff's are different in size. If you made the proper changes (different axles, either a na to t2 driveshaft or t2 driveshaft and t2 tranny) then you could use the t2 diff. It depends on how much work you want to do. As far as performance the t2 and na viscous LSDs are going to be the same but the t2 axles which are shorter and thicker can withstand alot more torture. If you want a dominate setup then you need to do a complete t2 drivetrain swap.

 

i might be having the same problem as you. here's a thread on it:
https://www.rx7club.com/2nd-generation-specific-1986-1992-17/problem-halfshafts-lsd-498182/

does it sound like the same thing? if it does, and your noise is gone after replacing the diff, then i have a better idea that that's my problem as well. from what people said, it sounds like a diff problem, but i haven't gotten around to doing anything about it yet. so, let us know if you have any luck with your replacement diff.

oh, i also heard that someone else (dDub, i think) had this problem and eventually took it to a rear end shop and they diagnosed it as a problem with the differential rather than the halfshafts.

 

my gxl is s5 and has open diff =( i already invested in the mazdatrix d/s so im not lookin to drop more cash on a turbo drivetrain...i guess i just have to weld it up.

 

since you dont have an automatic anymore - there isnt a torque converter to dampen anything....

 

SO this is NATURAL. See im asking cuase i never had a 5speed FC both my first FC were auto. So im just asking to see if its normal or my diff is bad.

But regardless iima put the 4.1 LSD cuase its LSD which is better than OPEN diff lol .

Then ill sell the open diff and keep the 3.9 LSD from my auto as a spare just in cASSE this one goes bad

Thanks for the input guys

Jason NYC

 

sudden throttle response could cause what you are talkinga bout
is this the first manual car you have driven?

try going slow in 1st gear, give gas, let off, give gas, let off.....

 

yeah this is my first manual car. I do drive like that give gas let off give gas let off, cause my RPMS are high and my car is LOUD. My boy got a full road race system on his vert **** is so quiet , my car is LOUD, like honda status, so i drive in higher gears to keep the rpms below 3k.

Jason NYC

 

LAWL! I have nothing positive to add to this thread, but the honda status quote put a smile on my face haha

 

Well i dont like having a honda status. its loud like a honda but it still retains it distinctive rotary sound. So even though its loud like a fart can honda it still rotary sexy.

Jason NYC

 

The GTUs was still a NA and still has a NA diff, axles, and driveshaft. All S4 LSD's were clutch type. All S5 LSD's were viscous. Whatever type the NA got, the Turbo got the same, just bigger. 7" vs 8" in diff diameter.

The GTUs had the same brakes and wheels as the TurboII. It did not share any other drivetrain components like tranny, diff, driveshaft, motor, axles, etc... Maybe the steering rack and suspension. Maybe.

 

Here's the bucking, popping, etc. You don't have an anti afterburn switch. It goes on the clutch.

As far as the GTUs, Same diff, differant gears : 4.30:1