| Author |
Message |
'75 308 GT4 (Peter)
Intermediate Member
Username: Peter
Post Number: 1871
Registered: 12-2000
| | Posted on Sunday, June 09, 2002 - 11:55 pm: | |
Adjustments can be done with the drivetrain in the car, but replacement of synchros must be done with it out.
But before you decide to haul the thing out, drain the tranny and drop the pan and check shifter movement first. Make sure that's copesetic before taking the next step... |
Harry (Harry)
New member
Username: Harry
Post Number: 12
Registered: 3-2002
| | Posted on Sunday, June 09, 2002 - 4:06 am: | |
Thanks Paul and Peter!
Peter, are the gear shafts accessible while the engine is in the car? I suppose not. Means engine out for replacing the synchro rings? |
'75 308 GT4 (Peter)
Intermediate Member
Username: Peter
Post Number: 1870
Registered: 12-2000
| | Posted on Sunday, June 09, 2002 - 1:42 am: | |
I had the EXACT same problem.
This was before I did a major engine-out service.
Doing the required adjustments after installation, no more grinding into forth. |
Paul Newman (Newman)
Junior Member
Username: Newman
Post Number: 204
Registered: 12-2001
| | Posted on Friday, June 07, 2002 - 8:13 pm: | |
Who knows why 4th might wear out faster, maybe the previous owner drove around in 4th resting his hand on the shifter, which really wears out the shift forks and could cause syncro blocker ring contact with the cone wearing it out. Bear in mind, every time it grinds, you do more damage to the 4th gear dog teeth which rounds the points off. The blocker is cheap but the gear is big bucks and you may have to buy a trans to get the gear you need. Inspect the teeth closely. It is the same syncro but the purpose of the blocker is to speed up or slow down the floating gear you wish to engage to the speed of the output shaft to prevent the grind. Why it works better one way and not the other would be a guess on my part and its hard to invision without the gearbox in pieces infront of me but Ill give it a shot. Depending on the amount of mass the syncro is trying to control would have an effect. Is it carring more mass one way over the other - probably. Either way, pull the pan and look, measure clearance between the blocker and dog teeth for a minimum spec. |
Harry (Harry)
New member
Username: Harry
Post Number: 10
Registered: 3-2002
| | Posted on Thursday, June 06, 2002 - 12:13 pm: | |
In my '75 308GT4 the gears shift smoothly (with warm engine) except the shift from 3rd to 4th, particularly at high revs. I feel resistance and, if shifted quickly, a metallic noise. I suppose the synchro ring is worn. But what confuses me is that the downshift from 5th to 4th is smooth like the other gears.
Two questions: how can the synchro ring of the 4th gear wear earlier than the one of the 2nd, which is used much more? And why occurs the problem only at the upshift to the 4th and not at the downshift (isn't it the same ring)? |