Building Transmission Need advice

[JayRolla]

Im having a very good local shop build a tranny for me. Im not really planning on upgrading my evo16g so im not going to be making more than 350whp.

My question is with my setup would I need the 4 spider gear CD upgrade with the power I'll be making. Its pretty much the stage 1 shep tranny with a torrington bearing. Would the stock center diff take 5k-5500 rpm launch's. Its about an extra $400 for the spider gear upgrade.

Here is the build list on the tranny.

New 1-2 fork
Unbreakable 3-4 fork upgrade- 1G
New 3-4 fork- 2G
New all brass synchronizer blocker ring upgrade- 1G
New all brass synchronizer blocker ring OEM- 2G
Our own machined double synchro 2nd gear upgrade
New 1-2 synchronizer hub
New 1-2 synchronizer slider
New 1-2 synchronizer springs
New 1-2 synchronizer shoes
New 3-4 all brass synchronizer blocker ring upgrade- 1G
New 3-4 brass synchronizer blocker rings OEM- 2G
New 3-4 springs
New 3-4 shoes
New 5th gear synchronizer blocker ring with flipped slider
New seals
New tapered roller bearings on each end of intermediate shaft
New 1-2, 3-4, and 5-R roll pins
New center diff spider gear side shims and upper Torrington upgrade
Reset bearing preloads for maximum bearing and gear life
Replace all bell housing case bolts
All case and internal parts cleaned in industrial spin-jet parts washer

 

[GVR4592]

With that power level I think the only thing I would look into doing is double syncro's on 2nd and 3rd. Have you talked to Jack about it?

 

[JayRolla]

Yea but he always reccomends the spider gear upgrade. He has seen them fail on low hp cars but these where old abused trannys. He also reccomends double synchros in 1st and second if thats all that is in the budjet. I asked how much for 3rd and he said he would do 1st.

 

[GVR4592]

I don't see any reason to do 1st unless you're autocrossing or roadracing. How often do you need to downshift into 1st at high rpms? 2nd gear gets the most abuse so it's a given that it should be doubled, 3rd is at an odd angle and it's an easy gear to miss when you're in a hurry, a double syncro on 3rd seems more beneficial than 1st.

Jack knows far more about our transmissions than I do and if he's giving you good reasons to go with the 4 spider and the double on 1st then I would take his advice. It's just my opinion that a double syncro on 1st gear isn't as beneficial as doing it on 3rd gear.

 

[JayRolla]

Yea thats why I wanted to do 3rd. He said its real nice to do first because its a real pain to into gear even when rolling sometimes. Im thinkin of just doing second and third but im still not sure If I need the upgraded CD.

 

[raped]

If you drive the car on the street a lot you may want to get the double synchro first gear. I know i hate having to come to a complete stop then having to wait for it to go into first. If this bothers you then consider the ubpgrade. I know i like to roll stop signs.

 

[raped]

also, if you plan on staying with the 16g then you don't really need the double synchro 3rd. The double synchro 3rd is only needed when shifting at high rpms.

 

[yokotabrat]

I think the big question for your decision on upgrading the center diff is, do you plan on launching the car a lot? If so, then I'd say upgrade it. I broke mine at the track with my B16g because of wheel hop. The tranny had around 30k on it. It's hit or miss with the center diffs. I've known people break them on a 14b, I've known people not break them with a 20g. Track/road conditions, launch techniques all affect your launch. If you want the peace of mind to be able to do a stutterbox launch at 11pm because your trying to intimidate the WRX next to you, I'd say go for it.

 

[JayRolla]

Yea thats what my mechanic tells me. I hardly ever launch my car, and I cant really afford the extra $400. Ive done quite a few hard launch's on my old 100,000 mile tranny and the center diff is still ok on it.

 

[yokotabrat]

Launching on the street is usually more forgiving than on a prepped track. Nothing wrong with holding off on the center diff. Worst case, you can pull the diff with the tranny in the car if it does break. Good luck.

 

[JayRolla]

Not a bad idea. I usually dont even launch that hard. 5500rpm with a little slip of the clutch. Im thinking of going without the 4 spider CD, I cant afford it. Anyone else with some helpful info.

 

[JayRolla]

So does anyone else think its a bad idea to skip the CD upgrade?