I Just Recently Installed Some Racing Beat 4.30 Gears Into My 93 Rx7 When I Did The Differencial Rebuild I Was Just Wondering What Are The Goods...? And Bads??? About It

 

i'd hope you researched before you bought, but it's alright, you didn't mess anything up.

https://www.rx7club.com/showthread.p...ht=gear+ratios

scroll down to my "spread sheet" post. (done manually since i don't actually use a spread sheet program).

you'll also see a gear ratio calculator that i used posted above that.


basically, quicker acceleration, lower top end, slightly higher revs per highway cruise speed.

 

what kind of difference will i see with the 4:33 gears will it be noticeable ?

 

if you use the calculator, you should see that the difference between 4.30 and 4.33 is so minute you wont notice it. 4.30 over 4.10 is actually a rather small step too, you'd mostly just notice it when at highway cruising speed. but it's a much more noticeable step if you've done a auto-to-5speed swap and then are doing 4.30's in place of the 3.90's, obviously.

if you are running a big turbo, a higher (slower) gear should also help you get into the spool range of the turbo, and of course, increase your torque modifier to the ground.

so with the 4.30 over the 4.10, you'll have a little bit more torque in the lower gears, and a little quicker acceleration, but you'll be shifting at a slightly slower gear. but since you are just shifting into 4th by the end of a 1/4 run with the 4.10, the 4.30 wont make you have to shift another time. which is something to consider if you are a hardcore drag racer.

 

I've read that by chaging the final gear your spd meter will not read correctly...

 

I thought the stock gearing (manual) was a taller gear, meaning you accelerated slower in 5th, but had a greater top speed, while the shorter gear allowed for better acceleration through 5th (great for serious road racing haha) but a lower top speed...

 

We are talking final drive ratios (in the rear differential) which affects you no matter what gear you are in. Basically, for a given speed (mph) your RPMs will be higher. In each gear you will redline at a lower speed, but will get there more quickly.

I have always stayed with my 4.10s b/c they are set up perfectly for around town and highway cruising. With the 4.30s you will be at a higher rpm for cruising. Of course, IIRC our FDs are gear limited to like 195 mph which no one sane wants to try to touch (170 mph is my max thus far) so going with the 4.30s does help on highway pulls.

Partially b/c of my parallel twins and all my other mods that have shifted my powerband upward I will prolly go with 4.30s when/if I swap in my new S4 TII diff I have sitting in the garage. The swap is quite the pita however.......

 

Oops..thanks for clarifying. Is what I was talking about just the 5th gear ratio?

Of course, IIRC our FDs are gear limited to like 195 mph which no one sane wants to try to touch (170 mph is my max thus far) [/QUOTE]I guess i'm insane then lol. If my new setup makes enough power, I'm absolutely gonna have a written will and find some controlled conditions to make a top speed run. I got a couple ideas of how to arrange the controlled conditions already

Rich, I take it you're referring to swapping the gear itself, because I thought swapping the stock diff for a Tii diff was a drop-in...

 

well, it's not quite as easy as all that. You are looking at some serious labor to have the TII diff 'dropped in.' The final drive ring and pinion are located within the diff pumpkin. Check this link out and scroll to the bottom:

http://www.rx7.com/store/rx7/fddrivetrain_rearend.html

 

Isn't this pretty much what I said tho?

We also offer different final drive (rear end) gears for nearly every street/racing condition. Adjusting the final drive gear ratio on your RX-7 will alter the acceleration and top speed. You can think of it almost like a 10 speed bicycle where the lower gears let you accelerate quickly but limit top speed whereas the higher gears are hard to get started (poor acceleration) but net a high top speed. For manual transmission cars, the stock final drive gear ratio is 4.10 (3.90 for automatic). Going to a different gear such as the 4.30 found in the Japanese spec cars will result in faster acceleration and a lower E.T.

 

Maybe I misunderstood what you were trying to say.....I wasnt really correcting what you posted, but elaborating on it---going with a numerically higher final drive ratio affects all facets of driveability, not just 5th .

 

Rich, it was my mistake. I was under the impression (due to the lack of mechanical know-how) that ppl switched out a single gear (5th) w/ a shorter one. You explained that they're changing the final drive ratio, thus affecting ALL the gears, including 5th, and hence acceleration and top speed... Thanks for the clarification.

 

When switching to the higher (4.10 to 4.30-33) Doesn't first and second gear get squirrely traction-wise? I'm doing the auto to 5 speed swap and thinking of maybe keeping the 3.90 gears to make 1st and 2nd better for traction. Thank this is a good idea?

 

No not generally speaking. The turbos need revs to boost, a 3.90 will hurt you on the launch. We don't have enough low end torque for the taller gears.

What is your HP goal? Good rear tires are the key to traction. Good tires that are old will be hard and limit traction, same goes for new cheap tires.

I have 4.33 rear gears and run intake, DP, CB, ASP medium but only 10psi, no traction problems at all in 1st gear unless I'm turning.

Jeff

 

Working on getting to the 400 rwhp within the next couple of months, I just don't want to sit there spinning through first. Will def. get wider rear tires with good rubber. Anyone tubbed out the fenders and had the axles shortened that you know of?

 

Over 170 could be crazy... I heard of an RX-7 flipping at 190 while going for a high speed run on the salt flats. Gotta look at aerodynamics...

 

My Ford Motorsports 4.30 gears are awesome...

 

I always hear people talking about spinning through a gear or two, and this is on stock twins... My tires aren't exactly the best (Falken FK-451s, 245s front, 285s rear), and I have pretty much all the bolt on's running 13 psi, but it's damn near impossible for me to lose traction in a straight line. I can chirp the tires between shifts if I'm straight dumping the clutch, but that's about it. So what's the deal w/ all these ppl talking about burning thru gears?? Real bad tires?

I've seen 165, and it wasn't no thang lol. I prob have a false sense of security, but it wasn't bad at all. I'm def. NOT planning on doing this on salt flats. No offense to anyone, but that's retarded IMO. So little friction, you're looking at pretty much no traction. I wanna do it on ASPHALT (ie closing an excellently paved stretch of highway about 3 miles or so long )

 

I'm running 275/35/18 Yoko's in the rear and my diff is always posi for some reason. probably somthing wrong with it lol oh well free kazz lol but my car I can be in 1st and nail it starts going hits 4 grand and burns through to 8 in a sec. Same in second gear, getting on to an on ramp and accelrating through 2nd hit 4500 or so and it spins the tires and gets all squirely around 40ish or so. and then chirps pretty good going to 3rd. I can't even floor my car in 1st or 2nd and i'm still running stock twins on a street ported motor

 

Maybe it's the ported motor or somethin, but I have practically all the bolt ons, stock twins pushin 13psi, stock motor, and I've done a GAZILLION WOT runs. I don't lose traction, period (not in a straight line) Maybe the Falkens aren't too shabby after all

 

i'm only running 12lbs boost and it's all over the road from it spooling not dropping the clutch. just spins on the spool up. I"m gonna but some bfg drag radials or nitto 555r's cause it's not my daily driver anymore so I can use a soft *** tire lol. Or hell maybe try the falkens lol It's tuned by Steve Kan though had the engine replaced and ported at Gotham Racing. Maybe thats it cause it was no where near that fast before on the old engine.

 

About the messed up speedometer . . . is there anyway to fix this? Would a aftermarket rev/mph controller fix this? Dunno anything about this; so sorry for the dumb question.

 

No it doesn't mess up the speedometer. If your tire height is taller/shorter than stock, you can mess up your speedo because you are effectively changing the gear ratio.

I had 4.3 gears installed in my car when I swapped to a S4 TII differential. It definitely feels faster in 1st and 2nd gear; however, traction is a bigger issue now in 1st gear. My tire height is taller than stock, so 4th gear @ 8k is still over 140 mph for me. The 4.3 gears were a good fit for me because most of my "competitive driving" is done 40-140, so my car is in the best powerband for my type of driving. My fuel consumption is already ridiculous, so I'm not worried about that.

 

that 3.9 is great for the highway.

 

You will need over 400 rwHp
[/QUOTE]I guess i'm insane then lol. If my new setup makes enough power, I'm absolutely gonna have a written will and find some controlled conditions to make a top speed run. I got a couple ideas of how to arrange the controlled conditions already

[/QUOTE]