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Replacing Synchros In Gearbox

wgoos
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wgoos Enthusiast

wgoos

Posted
Posted

i am looking at buying a 93' R33 GTS-T, it looks like a great car, recently had a new engine installed with 90,000 on the clock, the only problem is in the description the guy explains that the Synchros in the gearbox are starting to let go but the car is still driveable, what kind of issues am i looking at here? can i easily replace the synchros & how much would i be looking at? i can do all the labour myself just need a price indication.

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https://www.sau.com.au/forums/topic/356438-replacing-synchros-in-gearbox/
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75coupe Grand Master

75coupe

Posted
Posted

$1500+ for a rebuild approx, you can do it yourself if you know how to rebuild gearboxes...

then you would probably want to put in a new clutch and fluid at the same time, depending on power $400 for stock clutch, $900 for 300rwkw clutch... plus machine flywheel, spigot bush replace etc...

PaulosECR33 Community Regular

PaulosECR33

Posted
Posted

doing synchros is a big job unless you know what your doing... im not questioning you ability but if your asking how hard it is then maybe you should pay someone to do it... parts alone are very cheap.. if your just doing synchros but when stripped the box may need bearings etc...

Bl4cK32 Grand Master

Bl4cK32

Posted
Posted

The only labour you can do is remove the gb, remove/install new spigot bush, remove/install new clutch, bleed etc.

You will only get so far in rebuilding the box yourself, and end up taking it to somewhere to finish the rebuild. Do a search here and its the general consensus that the only people who bother to do this have experience and all the tools already. Syncros and bearings would be done together at a minimum.

wgoos Enthusiast

wgoos

Posted
  • Author
Posted

yeh thats what i thought about $1500 for a rebuild, i might ask a couple of mechanics that i've delt with in the past how much they will do it for if i remove the box myself & supply the new synchros, i do know what you mean about getting half way through something then realising you will never be able to do it as good as a professional.

75coupe Grand Master

75coupe

Posted
Posted

I dont think its 'do it as good as the professionals' I think its more not being able to complete it at all...

the gearbox needs specialised tools...

Im sure I read somewhere on here that the gearbox factory did decent price on full rebuild if you supply just the box.

Birds Grand Master

Birds

Posted
Posted

Don't even attempt it if you've never built a gearbox before and have no plans of building other gearboxes frequently in the future. It's not something worth learning unless you plan to rebuild alot of them. All the manhours, tools and swearing won't be worth the $1200 you'd pay to get someone else to do it for you, and a better job of it :)

Just pull the thing out and drop it off to a gearbox workshop. And yes, remember to replace things so you can save on labour down the track. Thrust bearing + spigot bush/bearing are the most important...inspect clutch - replace if worn, machining the flywheel at the same time. If removing flywheel, also consider replacing rear main seal on engine.

  • Like 1
Nanogrip Collaborator

Nanogrip

Posted
Posted (edited)

Yeah my car's syncros are slightly spunked. I have searched and searched in Google (but not here in SAU, pardon if I should but didn't) but is there a gearbox from a different vehicle that can bolt it on without or slight modification? No one in this island has the expertize to re-fresh a gearbox and I'm afraid that my only options are to purchase a re-freshed one from the outside or do it myself. :yucky:

Edited by Nanogrip
blk94r33 Mentor

blk94r33

Posted
Posted

I dont think its 'do it as good as the professionals' I think its more not being able to complete it at all...

the gearbox needs specialised tools...

Im sure I read somewhere on here that the gearbox factory did decent price on full rebuild if you supply just the box.

Agreed, you'll need at least a good press/press kit, along with decent specailty tools (ie circlip pliers) to even attempt this. And if you haven't re-co'd a gearbox before it'll be a daunting task. They look all compact and pretty, but once you start pulling bits off it gets complicated. Not the kind of thing to attempt with a shifter and rubber mallet.

  • Like 1
PaulosECR33 Community Regular

PaulosECR33

Posted
Posted

Agreed, you'll need at least a good press/press kit, along with decent specailty tools (ie circlip pliers) to even attempt this. And if you haven't re-co'd a gearbox before it'll be a daunting task. They look all compact and pretty, but once you start pulling bits off it gets complicated. Not the kind of thing to attempt with a shifter and rubber mallet.

+1

turboedsloth Grand Master

turboedsloth

Posted
Posted

Have a look at this thread and it'll give you an understanding of how much work is involved in rebuilding the box,

http://www.skylinesaustralia.com/forums/topic/290880-rb25det-gearbox-crunching-into-4th-gear/page__hl__guilt+toy__st__20

Thats only half way through stripping the box also, i couldnt finish taking it apart cos my press tool buggered up.

webber Proficient

webber

Posted
Posted

I don't know, i have rebuilt a few myself.

I only ever use a 20T press, some pullers with some home made additions & bearing seperator plates, Circlip Pliers, Snap Ring Pliers, 6mm pin punch, feeler gauges + dial indicator & stand (which other than seperator plates i had all in my shed & can get away with just feeler gauges really not crucial to have dial indicator for re-assembly).

Worst bit with the RB25 IMO is removing the speedo drive hub, but after buying a bearing seperator plate the right size, and some high tensile threaded rod (it is about 310mm down the main shaft) that is now no problem either.

My Advise -

1) Don't be afraid of the job

2)Download repair manual

3)On your first box, take as many photos as possible of disassembly.

4)Put every nut, roll pin etc into bags labled clearly, & put them into boxes labelled clearly ie. selectors, countershaft rear, mainshaft rear, etc.. or you will give up and get someone else to finish it for you.

5)Don't necessarily follow the repair manual, make ammendments to suit what tools you have avaliable.(look on net how other people have done it)

6)on re-assembly USE repair manual to check all tolerances and shaft end play. then order thicker snap-rings numbers from manual or shim up as required to meet specs.

Housing & selectors takes 10 mins to remove and install, once removed -

start at rear of box, remove mainshaft & countershaft bearings & gears in order (can basically only take one off at a time) remove small countershaft counter shaft. remove speedo drive hub, press both shafts together until shafts come free (need a bit of solid bar to sit on end of the countershaft to make same length as mainshaft (just makes easier to press), remove countershaft & input shaft on mainshaft will come free also (roller bearing will drop out of the end so be careful). then disassemble the mainshaft front half per manual. Don't even have to fully disassemble if snchros look fine, just replace what needs replacing or may need in the near future. Re-assembly is reverse, any issues refer to the photos you took.

My recomendation is replace all shifter inserts (little spring clips on schroniser hubs), they are a large cause for crunches. and are only like $3 each.

If you get stuck, or need internal parts ie. countershaft or etc. Contact me, i have tubs full of parts & have spare snchros etc.. All of the main bearings are common ie. front, rear & center plate bearings - off the shelf at most bearing shops, some of the needle rollers are genuine only others are off the shelf i found NSK did most of them, but not all are brought in to AUS by NSK.

Order a front cover gasket & have some threebond 1104 or simular gasket goo handy for the sandwich plate. Then i run Castrol Multitrax (or vmx-m) in the abscence of synthetic fluid.

I am in the middle of changing my sites host, but once i get that sorted i will post it all up in detail. For anyone that seen my FS5R30A page on my RB engine number register page will know what detail i had on bits and pieces.

  • Like 1
Birds Grand Master

Birds

Posted
Posted

lol.

Good write up webber...DIY guide would be a great addition to the forums too. I do recommend people either practice on a spare box first or atleast do it to their own box when time isn't a factor, because it does need to be done methodically...nothin worse than putting a gearbox back in and having to take it out again because something isn't sitting right!

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