Rb25 Tranny won't shift in to second past 3k rpm

[rastaman]

I need some Rb tranny expert help!!!! Car won't up shift into 2nd above 3k rpm. Some times 3rd gear does the same too. It will shift fine if below 3k rpm. I changed tranny fluid but no change. If it is synchros what rebuild kit do I need ? Or what else could be causing this? TOB ? Clutch?

[Sforteen]

I need some Rb tranny expert help!!!! Car won't up shift into 2nd above 3k rpm. Some times 3rd gear does the same too. It will shift fine if below 3k rpm. I changed tranny fluid but no change. If it is synchros what rebuild kit do I need ? Or what else could be causing this? TOB ? Clutch?

3rd gear is most likely due to the transmissions "insert springs" google that..

These are the springs that ride on the inside of the transmissions synchro selector sleeve, they are known to pop out over time, without them, there is no pressure being put on the actual synchro ring. That in turn doesn't slow down or speed up the desired gear.

If your having a problem in 2nd gear its likely the same issue, but i believe they use a different spring setup, they are much more durable and maybe more likely you either have a flat synchro ring (no more taper left... bottoms out on cone of the gear upon inspection) or the actual synchro sleeve is shot.. you can also have bearing issues that cause problems as well and shift forks being bent or worn. It really should be torn down by someone that knows transmissions as there are alot of possibilities.

The Z32 300zx transmission (Twin turbo and NA versions) have the same internals as an RB25 (minus the outputshaft)

Ive rebuilt a couple of these tranmissions they are a PITA, but are very durable tranmissions. here is a link with TONS of pictures of a patherfiner transmission rebuild, which is nearly identical to the RB25 trans.

Good luck

http://beergarage.com/PathTransmission1Remove.aspx

[rastaman]

^^ thanks for the advice and help...

[BoredEE]

Sforteen,

When you rebuild a 300zx/rb25 trans do you ever get the original size rear C rings back in place?

The beer garage guy and I both had to get thinner C rings.

I'm thinking you need special tool to press the whole assembly together to get the original C rings re-installed.

[rastaman]

Also, is there a rebuild kit from Nissan with synchros and bearings..?? Is there a parts list somewhere ? Just want to make sure I get the correct parts..

[BoredEE]

No real kit from Nissan you have to buy them piecemeal, which I did from Courtesy Nissan.

Courtesy has nice diagrams that makes it easy to identify parts.

There are other suppliers (non-nissan) that will sell kits with and without bearings. Just search for 300zx rebuild kits.

[rastaman]

No real kit from Nissan you have to buy them piecemeal, which I did from Courtesy Nissan.

Courtesy has nice diagrams that makes it easy to identify parts.

There are other suppliers (non-nissan) that will sell kits with and without bearings. Just search for 300zx rebuild kits.
What year 300zx 1996 twin turbo?

[Sforteen]

I didn't have an issue with the C clip from what i can remember, the last time i was inside one of these was 2 years ago or so.. Its been awhile, all i did with mine was replace 3rd gear slider, all the brass and installed new bearings. it later shit out insert springs again, (i replaced them with used ones) so i bought a newer trans with the better synchro design.

[rastaman]

Can someone confirm this is the correct tranny code and rebuild kit for the rb25det transmission?

FS5R30A

[rastaman]

http://www.ebay.com/itm/like/321564639755?lpid=82
Correct kit?

[mogli9000]

Break open your transmission and find what is broken first before paying.

300zx and rb25 = interchangeable.

If its listed a z32 kit, THEN its on the sellers end for selling you something that won't fit.

Just buy another transmission.

Not worth the time or money to rebuild unless you really want to stick with that tranny.