white944s2

All,

While at a DE this weekend, I suddenly had problems down shifting while under heavy breaking. Was hoping to get some input on possible options based on the following observations.

1. Again, won't go into lower gear without force while heavy braking. No grinding noise when doing so. It just doesn't flow down. Observed through most of the gear range, 5th to 4th, 4th to 3rd and 3rd to 2nd. Didn't try 2nd to 1st. On the upshifting, there was some minor change in feel (slightly harder) when moving up through gears.

2. Slack in gears when lightly accerlating and then letting off gas; back and forth. Not immediate as before. Some loud rattle noise after releasing throttle and engine brakes the trans. Test was run in 2nd gear.

3. Smooth shifting when car is off. No grinding when shifting gears.

4. No visual issues seen under car. Nothing leaking, no loose cables. Exhaust looks good. Catalytic converter does not rattle.

5. No slippage of clutch or similar feel once car was in gear. Clutch pedal has not discernable change in feel.

6. While at DE, no missed shifts while driving that would cause concern.

Any thoughts of possible diagnosis would be helpful. I have another DE in a month and need a quick remedy. Car is at mechanic but won't have any word until later next week.

Kev

schwank

Have you changed the trans fluid in a while? No technical reason that should cause the problem but my old tranny seemed to shift easier when I swapped the fluids for some new MT90.

Z-man

Kev:
Are you doing a heel-toe rev-matched downshift?

-Z

white944s2

Z,

Yes. Heal-toe during the run session. When I tested on regular road, I wasn't trying to H-T. Either approach resulted in the same finding.

johnmhudson111

might check to see if transmission is shifting causing part of the shift linkage to bind up.

Will Feather

I would change the tranny fluid for the hell of it. Then check from the linkage from the transmission all the way to the lever, something along the way could be binding up when all the weight is thrown forward from the inertia of hard breaking.

dmalo810

I haven't been under the car lately, but doesn't the hydraulic system for the clutch work with brake fluid from the brake reservoir? Since your having this issue under braking, maybe the brake system is robbing the clutch system and your not getting to fully disengage the clutch, causing the shift to be hard.
Maybe a reach but something to check. Bleed the clutch system.
By the way, you should change your brake fluid after a couple of DEs.

dillon410021

+ 1

white944s2

I'm very diligent with all of the fluids. Oil and brake are changing every two events. Brakes are bled after every event.

Kevin

dmalo810

Great. But did you bleed the clutch slave?

white944s2

Did not.

aben8057

I would lean towards the hydraulics being that is the continuity between the clutch and brake. Look around for any leaks on the master or slave cylinder, check hoses. Then if all looks good I would bleed the system.

Makis

Clutch and brake circuits are independent. Could be that the engine mounts or tranny mount is shot so under heavy breaking the selector could get stuck.