Mazda Rotary Club

General => General Technical => Topic started by: ratty_ratty on April 25, 2008, 02:34:39 PM

Title: gearbox
Post by: ratty_ratty on April 25, 2008, 02:34:39 PM
got a problem with me box

when i go from 4th to 5th it grinds like no tomorrow

but if i was to put it from 4th to 5th slow and try to get the stick close to the left of 5th gear i can it is fine

is it time i need a box or does something need adjusting

and if i need box any ides how much roughly i can get one for

thanks people
Title: gearbox
Post by: SiH on April 25, 2008, 02:49:56 PM
Mine does this too :( I had a 200sx before though, so i\'m used to it :D

Think it may be the synchro\'s.
Going to try changing the box oil and see if that helps :)
Title: gearbox
Post by: ratty_ratty on April 25, 2008, 04:12:34 PM
ok thanks buddy i will try this as well
Title: gearbox
Post by: Bobbit on April 25, 2008, 04:15:33 PM
It\'s the syncro, it\'s a common fault going from 4th to 5th, new oil does help, if you use thicker oil it really can help but takes longer to warm up.
Title: gearbox
Post by: Andy_k on April 25, 2008, 05:26:38 PM
Yeah syncro as others above have said, have a look on rx7club.com they use some good fluids that help.
In the long run though it will need rebuilding/replacing.
Title: gearbox
Post by: feelio on April 25, 2008, 08:37:58 PM
Mine does it too......syncro!

If you double clutch it won\'t grind!

I found this web site, have a look at how to change the syncro. I haven\'t read it through thoroughly so you will have to see for yourself if it\'s useful. Hope it helps.

http://www.3rdgenrx7.com/
Title: gearbox
Post by: SiH on April 26, 2008, 08:37:40 AM
Surely double declutching won\'t really help going up through the gears?
Mines worst when skipping 4th (yeah, i know, i shouldn\'t...) - i.e. blast in 3rd then knock it into 5th to cruise on the motorway.
Title: gearbox
Post by: feelio on April 26, 2008, 08:50:24 PM
QuoteSurely double declutching won\'t really help going up through the gears?

Works for me.....you\'ll have to try it! It just stops the annoying noise when you change from 4th to 5th!
I think it matches the gearbox to the engine revs. Not sure how it works, maybe someone else will confirm and explain.
Title: gearbox
Post by: rx7boy on April 26, 2008, 09:40:22 PM
I have the same on mine, have been told by a gearbox specialist that if you take ur time moving from 4th to 5th then u will get less of crunch, i have tried this and have had some success but everyso often it still goes. Bobbit your right thicker oil really does make a difference but eventually you will nead to rebuild, to rebuild the gearbox it will cost you about £600 excluding any new parts that are needed, does come with 1 year warenty but u have to be without ur gearbox for upto 4 weeks.
Title: gearbox
Post by: Nik da Greek on April 26, 2008, 10:29:49 PM
My last FD did this, had it for two years and it never got any worse. It was always on my to do list, but fortunately I wrote the car off before it became a pressing issue. Alls it means when the synchro goes is that it\'s not matching the speeds of the two cogs together properly, so they graunch a bit whilst one forces the other to spin at an identical speed, which is why double declutching in theory allows them to have a bit of a pause and find their own speed together cos the drive load is off them.
 
Did that make sense? I\'ve just had one of those "I\'ve read back my own post and it sounded like gibberish to me, how\'s anyone else got a chance" sort of moments
Title: gearbox
Post by: Ricco_04 on April 27, 2008, 09:37:34 PM
Would it be syncros if its difficult to go from 1st to 2nd or just crappy oil?
Title: gearbox
Post by: Nik da Greek on April 28, 2008, 12:11:09 AM
Synchros are usually accompanied by a very distinctive graunch, like when you go into reverse and the cars\' not quite stationary. In theory, they can go between any gears, but the change to fifth is most common. I think second to third is prone to it, too. If your first to second is just really stiff and doesn\'t grind, it could well be something else, the synchro going doesn\'t really make the change any harder, it just makes a nasty noise. Mine\'s a pig to get into second until it\'s all warmed up then it\'s fine. Could be a problem with clutch engagement or bleeding, maybe?
Title: gearbox
Post by: Ricco_04 on April 29, 2008, 04:34:21 PM
Ah I see.  Thank you for that :Thumbs-up

Mine does get better once oil has warmed up.  Guess a good gear oil change and also clutch/brake fluid change should sort that out.  As you have described then my syncros sound ok :)

Dam that reminds me, I need an uprated clutch!
Title: gearbox
Post by: ratty_ratty on April 30, 2008, 11:23:17 AM
what is the best gear oil to use??
Title: gearbox
Post by: David Nock (RIP) on April 30, 2008, 11:56:07 AM
FB loves 75W 90 full synthetic gear oil. Castrol/Valvoline etc.
I think the FD is the same - check book. The important thing is full synthetic - it gives a smoother drive altogether.
Title: gearbox
Post by: Nik da Greek on April 30, 2008, 12:01:06 PM
It\'s worth changing the gear oil and the diff oil, especially if you\'re not too sure of the service history of the car. When I did them on my previous FD, the gear oil seemed ok (though it did help with the graunching gearbox slightly afterwards) but the diff oil was like tar! It didn\'t so much pour out the drain hole as plop out in one big sticky lump!
Title: gearbox
Post by: ratty_ratty on April 30, 2008, 02:05:19 PM
is the gear and diff oil the same type??
Title: gearbox
Post by: Nik da Greek on April 30, 2008, 04:00:28 PM
Can\'t remember the actual specs of the oils. I had my mechanic do the changes as part of a service. I got the grades from a users manual I\'ve got on CD and got him to order the oils in through his supplier. There\'s loads of manuals online here http://foxed.ca/foxed/index.php?page=rx7manual hopefully should be able to find the info somewhere in that lot!
Title: gearbox
Post by: David Nock (RIP) on May 01, 2008, 11:11:25 AM
The ratings for the FB are slightly different for gearbox and diff - 75W 90 in both but API GL4 or 5 in one and API GL5 in the other. So I use fully synth API GL5 in both. Check book for FD as I have no knowledge of them.
Title: gearbox
Post by: interloper393 on May 01, 2008, 11:58:04 AM
id like the info for the fd too plz if someone knows it :)
Title: gearbox
Post by: Nik da Greek on May 01, 2008, 05:56:05 PM
Sheesh! Here you go then. Hope this helps
 
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