Hey i have an automatic n/a s5 1990 gxl, I would like some info on changing the hoghead to a 5spd manuals, because the automatic has a 3.69 gear and the manual has a 4.11 gear, i would like to know how many mph ill lose on the topend. Currently i can do 140mph.

 

The auto is a 3.9, the manual is a 4.1.

Doing the calculations for a stock FC with 205/60-15 tires and holding at 7000 RPM (autos redline at 7k, right?) in a direct drive gear (1:1, which is third for an auto), we get:

3.9 Final drive - 131 mph
4.1 Final drive - 125 mph

So, you could lose about 5 mph. Keep in mind these calculations are rough estimates, speeds probably won't be exactly as given due to A LOT of other variables.

 

Is the final drive the same on N/A models as well as the TIIs?

 

Yes, with the exception of the 88GTU and 89-90 GTUs which were equippped with the 4.3 LSD Pumpkin

 

All manuals had a final drive ratio of 4.1:1, but obviously the actual differential varied between model and year (LSD, open, clutch, viscous).

 

Wrong, read my post above yours

 

Yeah, forgot the 4.3:1, and I eliminated my statement about the verts, too confusing. But are you sure the 88 GTU had a 4.3?

 

think if i wana make an automatic drag car a 4.1 is a must eh?

 

I don't believe the "88 GTU had the 4.33.

 

my rx7 can turn 7500rpm without a problem stock.

 

I dont think the 88 GTU had the 4.3 either. Anyway, the ring and pinion swap if fairly straight forward, but probably wouldnt be worth the time, money or hassle. You can get an open N/A 4.1 diff for about $50, or a LSD one for around $150.

 

this ited give my automatic some teeth at the drag strip?

 

o yea btw, sence its indipendednt supession, couldnt ya just drop the axles and replace the entire rearend without opening it up?

 

Yes....thats what Im saying. Just buy a 4.1 LSD rear end for around $150. And if you're serious about making your car fast, just bite the bullet and do a 5-speed swap. The auto tranny makes the FC an absolute slug, pretty much no matter what you do excluding a full custom tranny/converter setup.

 

im not a brain surgeon, i cant do that kinda stuff, i can change rearends, but in the end even a n/a 5spd isnt fast, 15.3 isnt fast at all.

 

Why dont you just do a 5-spd swap? 5 gears and better gearing and you can actually launch the thing.

 

Because hes an idiot.

 

wana come here with all the parts and do it yourself?

 

wana come here with all the parts and do it yourself?

 

To make your auto as fast as a manual you will need to spend alot more time and money than just swapping in a 5-spd. Besides while you are in there you can add an aftermarket clutch and put some Redline or other sythetic gear lube in there.

 

89-91 Auto came with a 4.1 check mazdatrix website here: http://www.mazdatrix.com/g5.htmRX-7

Stock Rear Axle Ratios
Year / Model Ratio
79-82 3.909
83-84 12A 3.933
84-85 13B GSLSE 4.076
85 12A 3.909
86-88 5-spd All 4.10
86-88 Automatic 3.909
89-92 Turbo 4.10
89-92 non-turbo, non LSD 4.10
89-90 non-turbo, viscous LSD, "GTUs" only 4.30
93-95 w/manual trans 4.10
93-95 w/automatic trans 3.909

 

I have a Mazda service manual that says otherwise. The only auto that had a 4.1 from 89-91 were the convertibles.

Jerry

 

The GTU doesnt have a 4.3 until now (for me atleast) muwhahahaha

 

ok im confused, whoes telling the truth?....

 

ok im confused, whoes telling the truth?.... and btw, i can afford a larg amount of money spent over a larg amount of time, just cant afford something huge all at once.