General Tech Grinding Gears in Shift From 1st to 2nd

[KVH]

My transmission following some adjustments and repairs is working great, but I’m getting some slight grinding from 1st to 2nd unless I slow down the process—I stop .5 seconds mid-way and then no issue.

I’m OK just doing that. But I want to ask: is the slight grinding in a fast-paced shift normal? Is it an adjustment issue at the slave cylinder (my slave plunger gap is definitely smaller than .1)? Should I just chill and keep shifting carefully as I’m doing?

Thanks all!

 

[dklawson]

If the grinding does not happen during the other shifts, it is probably a synchro problem.

Try double clutching between 1st and 2nd. The following is a brief overview in case you are not familiar with the process.

For up-shifts you push in the clutch and pull the lever out of gear and into neutral. While in neutral you let the clutch out very briefly, then immediately press it in again and select the next gear. The short pause in neutral with the clutch out gets the next pair of gears closer to matching speeds so you can select gears without grinding. The pause in neutral is very, very short. You don't have to or want to pause for a long time in neutral.

Double clutching while downshifting is more complicated. If you don't need to do it... don't. That process is similar but involves blipping the throttle while in neutral to speed up the laygear. I can do it but I never feel like I am doing it right.

 

[TR3driver]

A quick test for a dragging clutch:

With the car stopped, engine idling, depress the clutch and hold it down. Shift to a forward gear, then back to neutral, still holding the pedal down. Wait a few seconds, then shift to reverse. If the gears grind at all, you've got a dragging clutch (or pilot bearing).

Otherwise, I agree, it's probably a tired synchro ring. 2nd gear seems to usually wear the fastest. Doing slow shifts sure is a lot easier than changing that ring! (And won't hurt anything as long as you don't grind the gears.)

 

[Sarastro]

I still remember that my TR4A, bought new back in the 60s, wore out the second-gear synchro in a year or two. It wasn't covered under the warranty, so I just double-clutched through life. That synchro gets a lot of use, so it's no great surprise that it wears quickly. But in your case, I'd expect a worn synchro to show more problems in downshifting than upshifting. In my experience, those grinding problems most often are clutch-related.

 

[CJD]

I still remember that my TR4A, bought new back in the 60s, wore out the second-gear synchro in a year or two. It wasn't covered under the warranty, so I just double-clutched through life. That synchro gets a lot of use, so it's no great surprise that it wears quickly. But in your case, I'd expect a worn synchro to show more problems in downshifting than upshifting. In my experience, those grinding problems most often are clutch-related.

Brings up a good point. These are far from strong gearboxes. It is smart to do the pause shift (or double clutch if you prefer) at all times to extend the life of the synchros. After all, you aren't going to win many races with a 12 second 0-60mph time! I personally don't double clutch up, I pause. But I do double clutch on down shifts.

 

[pdplot]

I thought you were talking about the Alfa Spider gearbox. They all do that. Can't hurry that shift into 2nd or you get a real graunch. Something about the Porsche synchros Alfa used. Just take it easy or you'll wind up with a covering of metal bits on your magnetic drain plug.

 

[Geo Hahn]

My transmission following some adjustments and repairs is working great...

Did you replace the 2nd synchro as part of that? Seems counter-intuitive but in my experience a new synchro can also exhibit this behavior at first then it goes away after some use.

If you did not replace that synchro then yeah, likely just worn and slow 1-2 shifting is an easy adaptation.

 

[KVH]

I’m curious what is meant by a dragging clutch? Is that an adjustment or a wear issue? Or neither?

 

[CJD]

A dragging clutch is a clutch that does not fully release. It releases enough to allow the car to stop with the tranny in gear, but if you are stopped, it would be difficult to take it out of gear, then it turns the tranny with enough force to grind the gears when attempting to shift back into a gear.

Dragging clutch can be caused by:

1) Improper adjustment
2) Worn slave or master cylinder
3) Air in the clutch system
4) warped clutch plate, disc, and/or flywheel
5) Slave cylinder attached to the longest hole on the clutch arm

When you asked if it was a wear issue...it could be. If you get a ton of slop in the linkages, then it is possible.

 

[KVH]

A dragging clutch is a clutch that does not fully release. It releases enough to allow the car to stop with the tranny in gear, but if you are stopped, it would be difficult to take it out of gear, then it turns the tranny with enough force to grind the gears when attempting to shift back into a gear.

Dragging clutch can be caused by:

1) Improper adjustment
2) Worn slave or master cylinder
3) Air in the clutch system
4) warped clutch plate, disc, and/or flywheel
5) Slave cylinder attached to the longest hole on the clutch arm

When you asked if it was a wear issue...it could be. If you get a ton of slop in the linkages, then it is possible.

Hmmm. I did relocate the slave rod to the bottom hole if the clutch arm. It seemed more “square” to the action in that location. Are you saying that could be my issue?

 

[CJD]

It very well could be. If you re-locate, remember you have to re-run the adjustment procedure.

 

[TR3driver]

There should be an adjustable brace from the slave cylinder up to a pan bolt. You can probably adjust it a bit to bring the slave square to the middle hole.

Usually, lack of travel (due to wear, wrong hole, etc) will show as the clutch engaging with the pedal very near the floor. If yours doesn't engage until the pedal is up off the floor, your problem probably lies somewhere else.

Sometimes, it can be just rust & dirt on the splines causing the clutch to drag. Driving around town (meaning lots of stops & starts) for a half hour or so might free it up.

 

[glemon]

I will add on the 2nd gear thing, my 4a had that issue too. I still remember (and this was over 30 years ago!, but now I can't remember if I brushed my teeth or put on deodorant in the morning) that if I shifted from out of first at 3000 and waited until it dropped to 2000 for second I would get a perfect shift nearly every time.

There is also a "feel" if you are sensitive with the box, waiting to avoid the crunch but the box should tell you when it is good to go. As the synchros engage you will get a little resistance, if you let the resistance win just a little (as in don't force it into gear) until the resistance gets slightly less it should engage with little or no crunch. While it is certainly nice to have strong synchros in all gears, there is also something satisfying to the art of matching revs to the box--but it does get a little dicey if you let others drive your car, as most won't be sensitive the little quirks, and the crunches are a little uncomfortable for all involved.

 

[sp53]

I thought a tr4 had a 1 inch slave cylinder? You are saying yours is smaller. If you are supposed to have I inch slave and I think you are, I would change to what it is engineered for. Many years ago I used a 7/8 slave cylinder for a tr6 on a tr3 because that is all there was available new at the time, and I had all kinds of problems. Most of which use it took a lot of force to get the clutch in and I think might ground between gears shifting. The 3 finger clutches are different and use a 1inch slave cylinder. It might be worth a try.