Hi there!

I've heard of people having problems with 5th gear synchros in FD's, but mine has started grinding into 4th. Has anyone else had problems with this?

I can't understand why my car is so hard on gearboxes! I stripped 3rd gear completely just a few months ago

Rob.

 

You stripped the 3rd gear ? What were you doing ? Drag strip ? How much power are you putting out ?

 

Hm. Does your car have its hand on the shifter ****, or do you?

 

If you are engaging 4th gear okay and just grinding as you shift into 4th gear, then it means your synchro is going bad. Synchros are like gear brakes that stop the gears from spinning momentarily between shifts. They are also somewhat fragile. As a result, if you have misshifted a number of times (or once big time), then it will not take long to damage the synchros.

 

If you are engaging 4th gear okay and just grinding as you shift into 4th gear, then it means your synchro is going bad. Synchros are like gear brakes that stop the gears from spinning momentarily between shifts. They are also somewhat fragile. As a result, if you have misshifted a number of times (or once big time), then it will not take long to damage the synchros.

 

If you are engaging 4th gear okay and just grinding as you shift into 4th gear, then it means your synchro is going bad. Synchros are like gear brakes that stop the gears from spinning momentarily between shifts. They are also somewhat fragile. As a result, if you have misshifted a number of times (or once big time), then it will not take long to damage the synchros.

 

Do they stop the gear from spinning momentarily ,or do they match the rpm of the gears before the shifter block engages the two sets of teeth . How does the gear stop ? Think that over .Match rpm or stop the gear .

 

I would defer to a transmission expert, but I think they actually stop the gear as the disengaged gear is not spinning. How else does that disengaged gear get up to speed with the spinning gear?

 

duboisr, you are more right than I am. After thinking this through, the syncros transfer friction from the shift collar to the gear face so that the collar teeth can mesh into the gear face. Once the vehicle is moving, the actual gears in the transmission are constantly rotating. The collar is fixed to the drive shaft so during a shift you are trying to insert the collar teeth into the face of the gear (which is also spinning). Hence, when you shift, the synchro serves to bring the collar speed up to the speed of the spinning gear. Thus, the synchro operates more like a mini-clutch rather than a mini-brake.

Thanks duboisr! I really needed to spend my afternoon figuring out how a transmission works.

 

You are welcome , my mechanic and advisor for info is really sharp. Learn to repair transmissions and you will have a sellable skill .

 

dgeesaman: point taken, but I don't think i'm particularly harsh on the gearbox, shifts are fast but smooth.

power is somewhere around 450hp i guess.

The only other thing that i can think of is the transmission brace I have which mounts the gearbox solidly to the chassis. This might be stressing the gearbox excessively. Does anyone know much about the integrity of our gearbox casings?


Rob.