trd 4.77 gearing, worth it?

[eightsixboy]

I am keen on getting the 4.77 gearing after converting to 4.1 from 3.9 and being surprised by how much difference it made.

i have heard of people having problems with bearing noise after a spirited drive and having to get the preload re done. And i heard one guy got so pissed with it after it been taken out like 4 times he just sold the gearing lol.

So are there any issues with it?

[federal]

the issues will not arrise if the backlash etc is set correctly

[Jonny Rochester]

It is very common that after someone puts in a LSD, or changes the ratio etc... that there becomes diff noise. It happens with me also. One reason is that the crownwheel and pinions we play with are often second hand anyway. And it has to be setup with correct preload, and backlash, and pinion height. And contact pattern checked.

Normaly you are suposed to adjust it with the contact pattern in the middle of the tooth. But in Carrol Smiths books (Tune to win etc...) he surgests for race cars the contact should be towards the front of the pinion. So that when the diff is constantly loaded, and there is some gear seperation, things wear more evenly. He also talks about rounding off sharp edges of the gears with a stone.

Also, after most of us do a full practice day at the track with a otherwise good diff, we get a diff noise on the way home from the track. Sound familiar?

Group A and N2 cars had a diff oil cooler. Maybe for good reason, not sure.

I think if your motor will be reved over 8000, and your top speed is not over 180, then the 4.7:1 diff will be great. It's not too hard to work out the top speed and rpm with a spreadsheet.

[ae86-matt]

i wouldn't go for anything less than 4.3, from personal experience, but again it comes down to what your intended set-up is.

just as a side note, i was at a recent track day and an 86 there had a 5.4 ratio!!!!, acceleration was nuts

[slydar]

depends on your engine set up. for a 20v i think thats still a little too short, maybe something with really big cams.

4.3 is really the best, maybe 4.5, but ive been in a car with 4.77 (stock blue top, fresh motor with quad throttles on adaptronic) and i didnt like it.

depends where your power band is.

[charged]

Ive just changed to a 4.77 from a 4.11 on my car and it works great on the track, heres the ratio spreadsheet

here a link to the gear caculator
http://locost7.info/gearcalc.php



heres the chart for 185/60/13 tyres, t 50 box a 4.77 ratio and 9000rpm redline




GearCalc v2.0.0.1 Copyright ©2001, Peter Ogden
Gear Ratio, Speed and RPM Calculator

Gear set: Manually entered values
Gear 1 2 3 4 5 Final
Ratios: 2.347 1.733 1.379 1.144 1.000 4.770

RPM Limit: 9000
RPM @Peak Power: 8600
Tyre Size: 185/60 x 13
Tyre Diameter: 552.20 mm
Tyre Circumference: 1734.79 mm


Gear Km/h per 1000 RPM Km/h @8600 RPM Km/h @9000 RPM
--------------------------------------------------------
1 9.30 80 84
2 12.59 108 113
3 15.82 136 142
4 19.07 164 172
5 21.82 188 196

Km/h RPM (in Gears)
-------------------------------------------------
1 2 3 4 5
-------------------------------------------------
10 1076 794 632 524 458
20 2151 1588 1264 1049 917
30 3227 2383 1896 1573 1375
40 4302 3177 2528 2097 1833
50 5378 3971 3160 2621 2291
60 6453 4765 3792 3146 2750
70 7529 5559 4424 3670 3208
80 8604 6353 5056 4194 3666
90 7148 5688 4718 4124
100 7942 6320 5243 4583
110 8736 6951 5767 5041
120 7583 6291 5499
130 8215 6815 5958
140 8847 7340 6416
150 7864 6874
160 8388 7332
170 8912 7791
180 8249
190 8707

Gear Change RPM drop (change @8600) RPM drop (change @9000)
-------------------------------------------------------------
1 -> 2 -2250 (to 6350) -2354 (to 6646)
2 -> 3 -1757 (to 6843) -1838 (to 7162)
3 -> 4 -1466 (to 7134) -1534 (to 7466)
4 -> 5 -1083 (to 7517) -1133 (to 7867)

[eightsixboy]

cool thnx for the info guys :2thumbs: .

The 4.11 gearing i got now is pretty good, maybe just a bit to long though, i would love 4.3 but as we all know its hard to get. I have never seen 4.5 before!

It also comes down to the gearbox to, 4.1 would feel alot better with shorter gear ratios i'm guesing.

I thought that for the money, 4.77 looked like a much cheaper option to get decent acceleration than doing cams, ecu etc. i'm more concerned with whether i will be having problems with it or not?

[wideslider]

I had a 4.77 put into my diff and a month later I had huge noise,

I was talking to a mate who told me that the pinion gear has a crush type

bearing which can get play in it and cause the premature wear.

I have since had a solid item fitted and so far so good.

[Jonny Rochester]

That is a excelent thought. The standard diff is ment to have a crush washer. You are ment to use a new one everytime you put it together, but they are often used secondhand. And I guess if a fair bit of power is put through the diff, the crush washer could move or relax.

I just got a secondhand diff from Japan, and saw a big thick solid washer in it. It would have to be shimed or perfectly sized.

Anyone know a diff expert to confirm the solid spacer thing?

[Vezza]

<div class='quotetop'>QUOTE (eightsixboy @ May 6 2008, 10:43 AM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=527145)</div>
cool thnx for the info guys :2thumbs: .

The 4.11 gearing i got now is pretty good, maybe just a bit to long though, i would love 4.3 but as we all know its hard to get. I have never seen 4.5 before!

It also comes down to the gearbox to, 4.1 would feel alot better with shorter gear ratios i'm guesing.

I thought that for the money, 4.77 looked like a much cheaper option to get decent acceleration than doing cams, ecu etc. i'm more concerned with whether i will be having problems with it or not?[/b]

A 4.3 is pretty easy to get on ebay, usually around 160-180 bux US and around 70 bux shipping