RB25DET synchro/clutch issue??

[johnny butt]

Hey guys,

I'm having a transmission problem and need troubleshooting ideas or confirmation of my suspicions. Here are some scenarios:

When driving, from a stop, I shift from 1st to 2nd, not accelerating quickly, low rpms, no boost, but I have to double clutch and 'wait' before I actually move the shifter into 2nd to avoid a grind.

When driving, from a stop, I shift from first to 2nd, accelerating quickly, full boost until redline, it shifts fine.

When car is off I can go from first to 2nd smoothly no grind no problems.

I change fluid pretty regularly, every 3rd oil change, I use redline mt 90. I have an rb25det transmission and spec stage 1 clutch installed October 2007. Motor is on stock turbo pushing 7psi controlled by hks evc 6.

Me, personally, it feels like under slow driving conditions the clutch is not disengaging causing synchronization issues.

Can anyone confirm my suspicions and recommend a solution? or recommend any other troubleshooting methods or possible problems?

Thanks.

[johnny butt]

Hate to bump a thread but surely someone has some ideas....

[240z4u]

Does it grind from 2-3 and 3-4? I would think it would if the clutch wasn't disengaging. Sounds like a bad synchro to me.

[LSDrift]

Did you delete the damper? Also, are you noticing this when the trans is warm or cold?

[johnny butt]

Does it grind from 2-3 and 3-4? I would think it would if the clutch wasn't disengaging. Sounds like a bad synchro to me.

2-3 and. 3-4 under slow driving conditions it will grind if I don't press the clutch in twice between shifts.

Did you delete the damper? Also, are you noticing this when the trans is warm or cold?

Also, good question, I don't recall but the pedal is extremely soft, softer than most newer cars i have been in. I will have to check and get back to you.

Car is a convertible, originally automatic, and I know it wasn't something we picked up during the motor swap...it was just typical 5speed swap parts, clutch pedal, brake pedal, etc...also not something that came with the swap. I will have to physically check and see if its in place.

Clutch slave cylinder was replaced when we put the motor in in 2007.

Also, it happens with cold or warm trans.

[Glue]

when is the last time you change the clutch, it seem like the clutch is bad not synchros. let us know what the problem is.

[opticnerv]

I agree with glue it sounds like a clutch problem. Improper installation or worn clutch components can cause hardshift/gear clash. Especially since you can shift fine with the car off. Make sure to check your slave cylinder and how much fluid you have in the master.