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gearbox weakest link

Posted: Sun Oct 25, 2015 5:15 am
by oaasport
hey guys, ive seen so many posts about the altezza gearbox being weak. Was the TRD upgraded gearbox weak too? Im curious as to what makes this gearbox weak. Do people break gears? I've been told the circlips break. Ive been told it wont hold 300hp but there are people with plenty more power. Reason im asking is i got a quote for a custom gearset made for the car with any ratios. At $4500 USD its pricey. However i dont want to have a gearset made to find out its minor things that need adressed ( circlips, shift rails and forks) any help from the people who have broke them or made them last is appreciated

Re: gearbox weakest link

Posted: Sun Oct 25, 2015 6:08 am
by Soiled
Only time I've broken one was a missed gear change. Stripped a gear, bound up then snapped the input shaft.

As for the weakest point I'm not sure, as I only have my personal experience to go by and I tend to have some mechanical sympathy unlike other people. Don't slam through the gears or dump clutches and rev match on down changes when at any decent revs.

If you want to be hard on your gear changing to an R154 (Think they are around NZ$3k new from Toyota) and a custom bellhousing (NZ$800-1000) would be a much cheaper option and proven to last, or run factory box, run to failure then worry about upgrading if it happens.

Re: gearbox weakest link

Posted: Wed Oct 28, 2015 11:39 pm
by Trd Shane
Last week I stripped 2nd gear completely no teeth what's so ever and I'm running 270 Bhp and 280 ftlb .. There is People running much higher power on standard boxes .. Just luck of the draw really .. If you want a stronger box get the s15 box exact same box just swap bell housings .. Same box is in a lot of cars just different housings .. S2000 s15 and a few mazdas .. I was told the s15 is a stronger box than all just different ratios but I think they benefit turbo Tezzas .. (That's if your running turbo ) I replaced mine with a is200 box so let's see how this one fairs out .. Main front bearing is a failure in them also had two or three start to fail as in get noisey

Re: gearbox weakest link

Posted: Thu Oct 29, 2015 12:34 am
by oaasport
Hey soiled and trd shane, thanks for the input. You say you stripped a gear soiled and shane you said you stripped 2nd. By stripped do you mean the syncros gave out and then sheared the teeth off the planetaries? I've got a company here in the states that replaces the syncro with almost a dog type sleeve and gets rid of the syncro. They told me take that route first before a custom gearset which makes sense (1/4 the price). They did a w55 which usually is about a 350hp trans (ive broke 3 with an na-t 2jzge) and put the sleeve and ring on and its now held 650hp for 2 seasons. Mind you this is a drag car so it really gets beat on. Im trying to find a cheaper solution than a $4300 gearbox, although custom ratios would be nice

Re: gearbox weakest link

Posted: Thu Oct 29, 2015 11:56 pm
by Soiled
I released the clutch too early so the gear was half in changing from 1st to 2nd and stripped the teeth off the gear. Syncros were still fine.

S15 boxes are the same strength most Silvia guys chasing power swap for the S14 5 speed. So that could always be another option, but then you'd have to get custom clutch, flywheel, bellhousing and driveshaft too.

Re: gearbox weakest link

Posted: Wed Nov 04, 2015 11:31 am
by RS Tom-Hundred
Trd Shane wrote:I replaced mine with a is200 box so let's see how this one fairs out ..


Is the IS200 gearbox a direct replacement for the RS200 one then?

Re: gearbox weakest link

Posted: Fri Nov 06, 2015 9:30 pm
by Celica RA45
the alloy selector forks are the weakest link and also a cir-clip on the main shaft can drop out

Re: gearbox weakest link

Posted: Sun Nov 08, 2015 8:34 pm
by oaasport
Would having selector forks made of a stronger material help out? What aboht the circlips, what makes them weak?

Re: gearbox weakest link

Posted: Mon Nov 09, 2015 7:18 pm
by Trd Shane
No there not direct replacement.. You have to swap bell housings which is easy when you know what your doing .. Had it changed in 20 mins .. Only tricky part was putting in the locator bolt in it's really easy to knock the lever off when putting the bolt in but if you look at what your doing carefully it's a doddle to do .. Plus there cheaper to come across also

Re: gearbox weakest link

Posted: Thu Nov 12, 2015 11:12 pm
by hermit
RS Tom-Hundred wrote:
Trd Shane wrote:I replaced mine with a is200 box so let's see how this one fairs out ..


Is the IS200 gearbox a direct replacement for the RS200 one then?


The gearbox is the same but the bell housings are different

Re: gearbox weakest link

Posted: Fri Nov 13, 2015 3:10 pm
by RS Tom-Hundred
Thanks for the info guys, interesting to know! :)