OK, I haven't gotten the diff in yet, what a PIA. Actually it isn't a really bad job, it is just that I'm running out of elbow room in my garage.

Here is a pic of the diff, while it was torn apart I took it to the local sandblaster/powdercoater for a nice gloss black coating.

Hopefully I'll have it in tomorrow and I'll give a little update on what I think. I'm going to auto-x on Sat and Sun, that is the specific reason I got the lower gears, 2nd gear is just a little too tall while 1st gear is to short and unpredictable.

 

Let us know how it works out Jeff. At some point down the road I was hoping to do this too. CJ

 

Got the diff in tonight and took it for a short drive.

I'm totally pissed, the speedo is wrong....

Kidding, not a HUGE difference but I expected that. First gear goes by pretty quick, not much slipping of the clutch is required to get the car launched hard. I also had some brand new Hoosier race tires on the car, they are so much stickier than the Kumhos! No wheelspin at all in 1st gear, unless you try by dumping the clutch.

I'll let ya'll know what I think about them at this weekend's auto-x.

 

hey jeff,
thanks for the license plate tip a while back. ive been running without it since. the look, without a doubt is much better and the power is very noticeable, especially with the onset of this cooler weather.

now with regard to the 4.33 gear set: did you purchase it as a complete differential or is it a diy kit with a ring and pinion set. do you get other components as well, ie. gaskets, seals, bearings, etc. assuming that it was your undertaking the r&r, what equipment is required to tolerance the components. any special tools required. degree of difficulty 1- easy thru 10 - extremely difficult, what would you rate it.

looking forward to more data on how this rear end ratio change affects the cars performance. was original set 4.11 or 3.90.
chuck

fyi
im working on a project inspired by your good advice.
im prototyping a carbon fiber, supplemental air delivery system as a retrofix for the stock box. then ill cad it up, iges it out, run toolpath and cut a prelim mold.

 

Is there any speedo gear you could buy to correct the mph change? CJ

 

Can't our speedos be recalibrated to fix this?

 

I have a 4.33 gear in my car along with a KAAZ differential. I had my stock 4.1 differential completely rebuilt (bearings, seals) when I had the LSD and gear installed.

I love the 4.33 gears for the same reason that Turbo Jeff stated. But I HATE the KAAZ differential. If KD had returned my original stock LSD (like I asked them too) I would have it re-installed. The KAAZ unit works too well... It is loud and clicks terribly as a daily driver. But when launching it definitely puts equal power to both tires.

As far as the speed.... it is off by so very little that I doubt it matters. 2-3 MPH. Putting different size tires on a stock geared car would be similar.

 

If u look at the FD with the 4.33 R&P u'll notice that they come with larger tires.

So in short it would balance out.

 

Not in the USA they didn't.

Besides that... talking apples and ornges here. The topic was how the gears affected the speedo on our cars. Jeff didn't buy new rims and tires because he got the different gears to make the speedo read correctly

 

that was a given fact.

i think everyone knew that 4.33 didn't exist in the USA, or people wouldn't make an effort to even talk about them.

 

I had a TII diff. installed with 4.33 gears this week. I'm picking up the car today. I'll be sure to post up my impressions as well. My tire height is taller than stock (275/35-18), but I've always had this tire height, so I should notice a difference.

 

Hey Jeff,

Is the Auto-x in town? Valley River? I'd like to stop by.

Richard

 

It is in town at the Coke plant off Chad Drive.

I'll be there in the afternoon Sat and morning Sun. See you there!

 

Update after autocrossing my car today!

On the street:
I've driven the car for 2-3 days now on the street. I can say the biggest difference is that it is easier to launch the car hard without slipping the clutch as much. 1st and 2nd gear seem marginally shorter. Overall I'd say if you have a 4.10 like all 5spds it won't be a huge change. For an auto trans car I think it would make a HUGE difference in 1st gear acceleration off the line.

Autocrossing:
I WAXED the competition today, Fastest Time of Day and Fastest PAX Time of the Day. Some of that is the new Hoosiers, some of it is the gears. The course was typical of our local courses, long and narrow, that means you have to turn around U-turn style at the end, in a FD 2nd gear is too long to come out of the "hole" with much boost, many times I'm stuck on the 1st turbo for 1/3-1/2 of the straight. Now I can come out of the hole quicker and get the second turbo spooling earlier, it was very noticable on the auto-x course.

I've driven a FD with 4.88 diff but he has larger diameter rear tires (315/35/17 IIRC) vs. my car running 245/45/16, still his car had even lower gears than mine but it is not street driven, mine is so I went with the 4.33.

Bottom line, don't spend the $$ if you drive the car on the street exclusively unless you have no other mods to do. If you auto-x the car and find yourself working on the 1st turbo only in 2nd gear you'll love the shorter gears.

 

I wonder who makes the 4.88 gears. I got my 4.77 final from Amemiya.

 

Someone else has pointed this out to me. The owner of the car stated they were 4.88s, I know he got them from Japan so they might be 4.77s and he just remembers it wrong.

 

Who all builds a 4.77 ring and pinion set? I am looking at a car that has 4.77's in it....how streetable will that be? Top end? How much will the rpm differentiate from the stock 4.10's?

 

Amemiya's the only one I know of who makes the 4.77. Streetable is always relative to what you want your car for. My top end is limited to right around 160 mph(patiently waiting for JimLab to chime in on the exact mph).

 

well.unless youre planning on going faster than 160 they should be a good choice right?
im sure theres a good jump in accelaration from the 4.1 gears.

 

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

 

I have a 4.3 and will be switching my 5th gear to a .806 ratio from a Bathurst Rx-7, or you could use the 5th gear from the 87-88 TII which is a .762 ratio.

From Wargasm:
4.3 + .806:1 at 4K = 85 mph and a 170 mph top speed.
4.3 + .762:1 at 4K = 90 mph and a 180 mph top speed.

A 4.77 would make 1st gear way too short and you would still have the nasty drop off in power when shifting to 5th gear. With a 4.77 and stock tire height, your speed in 4th gear at 8k RPMs would only be 124 MPH.

 

I like the 4.33 rear end...just becareful on setting the back lash, it's damn tight to get it right. As far as telling the 4.33 is in there, the ol' butt dyno thinks it's pulls a tad harder and the dyno seemed to again with it since my torque number is 320 ft/lbs, a bit higher than a car with a stock 4.10 at the same power level since it is turning the rolls a bit faster.

Tim