Were any of the automatic 3.90 rearends LSD? If so which ones? Thanks

 

Nope, im pretty sure that was only available in the GTUs.

 

haha, no the GTus had 4.33 and auto coupes had 3.90 rear end, the covert autos have 4.10 however.

 

But were those 3.90's LSD or not?

 

I don't believe so. Why sould you WANT a 3.90 LSD??

 

and the '88 Vert. The only automatics 86-91 with LSD's were the S4 GXL's. The '88 Vert wasn't available with Automatic and did not come with LSD.

I pulled a LSD from a 88 GXL Automatic and checked by turning the half shaft mounting plate one turn and counting how many turns the drive axle mounting plate turned. It is a 4.1 ratio.

The only purpose I can see for the 3.9 is for mileage purposes. I put the 4.1 LSD in my '88 Vert, major seat of the pants difference in performance and little to no affect to mileage that I could tell.

In fact, I'm in the market for a GTUs 4.3 Diff and speedo gear (to maintain speedometer calibration) for my '91 AutoVert (stock 4.1 non-LSD) to goose up its driveability.

Anyone know what Factory mileage specs is for a 89-90 GTUs for curiosities sake?

 

Opps im getting my facts mixed up.

 

There's alot of misinformation in this thread.

88 Convertibles were only available with a manual transmission and the 4.1 LSD rear end.

89-91 Convertibles with a manual had a 4.1 rear end and the automatics had the 3.9 rear end. These were not available with LSD.

 

My 88 GXL (auto.) has LSD are you saying it's a 4.1???

 

including yours????

All the 88 verts only came with the 3.9 rear end that was an open rear end (non-LSD). LSD was not an even an option.

However you are correct in that there were no 88 automatic verts made for the North american market, they were all 5 speed manual.

 

No. All automatic transmisson coupes, came with the 3.9 rear end. With the GXL (on series 4 cars) you also got the LSD, regardless of transmission.

But if you had an automatic or a series 4 vert, you had a 3.9 rear end.

 

Just on this question I pulled a LSD from a wrecking yard 88 GXL and counted the driveshaft turns to half shaft turns.

Driveshaft turned just over 4 times. Checked it several times and the same. So, unless the previous owner had already swapped out the Diff, it looks like ALL S4 LSD's are 4.1.

I put it in my 88 Vert, thus converting from 3.9, and seat of the pants difference was very noticable. Also, if my Vert ever ends up in the boneyard, I've now added mystery to 88 Verts with LSD's. LOL

And the mystery continues.........................

 

Well see Hozz, that is exactly how it happens... some swaps something, then it gets wrecked and then the next guy swares that is the way they come.

Did you see that thread I posted on what the actual models and options were for all the series 5 cars???

 

Nope.

I am curious if Verts ever had Anti-lock brakes as an option.

What other not so well known nuggets of information did you share? Or, at least a link to the thread?

 

https://www.rx7club.com/forum/showth...hreadid=136126

Don't have the S5 one yet... But I will post it when I get it.

 

You have done the FORUM, if not the WORLD, a great service.

PM me when you post the S5 version so I can print it out for future reference.

Good job.

 

So thats how Gear Ratio Is determained? Interesting.

Why would a higher number be better? I mean, that means more area for a gear to make a complete circle as opposed to a smaller one that would make the wheel spin faster. Am I missing something?

 

Bigger the rear sprocket, the easier/faster it was to start. And the rear wheel rotated less per pedal rotation. But, you ultimate speed is slower when pedaling as fast as you can.

Smaller sprocket, harder/slower start. But, more rear wheel rotation per pedal rotation. So, more speed when pedaling as fast as you can.

Thus, if the driveshaft turns 4.1 times per single rotation of the half shaft (thus the wheel), the less strain on the engine to push the car.

Thus, quicker (read low end) start like the bigger sprocket bicycle gear. But, less high end speed when your Wankle is "pedaling as fast as it can".

Conclusion compared to 3.9 gearing:

4.1 gearing=quicker starts, lower top speed, lower gas mileage
4.3 gearing (GTUs)=even quicker starts, even lower top speed, even lower gas mileage.

My view, you get more thrill driving/driveability opportunites at lower speeds. But, most REX drivers don't have the wallet to support gas cost of daily freeway 4.3 gearing driving. So, 4.1 is the best compromise. Mazda apparently felt the same way, at least for 5 speeds and to compensate for Automatic Verts extra weight.

That help?

 

check my recently resurected thread on this subject. Apparently, technical sources suggest S4 GXL's with automatic did indeed come with a 3.9 LSD Diff.

So, the mystery continues...........

 

So In a way, having a 88 Manual GXL seems to compromise between having the best of both worlds In terms of top speed and quick launches?

 

My '88 Vert came with a automatic, (I bought it new in '88) even though the window sticker said it was a 5 speed.
This was one of the first Verts in the country. There must have been others.

 

but I KNOW you know the difference.

You, my friend, have just won the prize for the rarest RX7 in the US of A.

Icemark, you get this?

 

Ouch, I was just "treated" by Icemark. Honestly, I thought I was correct. Then again, the whole controversy over which S4 cars had LSD is obviously still raging.

 

^ cause I wanna know.

 

Must have been a dealer swap. No 88 verts came with an auto from the factory into the USA.

89 with the S5 bumpers lights and interiors were the first 'verts to come in with auto's.

The 88 was around $23K when new... If you could afford that back in 88 I suppose you could afford the extra $2k for a dealer to swap trannys.