Reverse grinding, why it happens and how to prevent it ?

[135sohc]

Ever since this car has been new reverse has had a bad habit of grinding on occasion. It can go weeks at a time w/o doing it and then start right up again. I know why it happens, the input shaft is still spinning and your trying to mesh 1 straight cut gear with two others. But why the input shaft, say even after 30 seconds+ of holding the clutch down is still freewheeling and thus allowing the gear clash to occur, but then other times I can go from 1-R half a dozen times when making a turn around and every time reverse drops right in without the grinding

Other day I dropped someone off and while waiting in the driveway I had the clutch pushed in for atleast 2 minutes, go to catch reverse and its a metallic B-ZING, CLUNK!! whole car bucked like it was stalling and then it was fine. Two+ minutes and the input shaft was still spinning. Clutch set and throwout bearing is whatever the advance auto stock replacement was for a TBI car was in 2005... currently has 55,000 miles on it. Could a warped flywheel with just enough of a high spot be allowing the friction disc to be 'grabbed' and flung around intermittently ?

[BadAssPerformance]

yeah, def sounds like it is still spinning... intermittently. if you move the shifter side to side that usually slows the gears down so they can mesh.

Maybe a warped flywheel... or maybe more likely a tweaked p-plate spring diaphram? like one side took a set so its partially engaged some how?

[mcsvt]

I always wondered why this was an issue as well. Going 3rd to reverse has helped reduce it, though that isn't really solving the actual problem.

[135sohc]

Wouldnt suprise me if the PP was defective, great chinese QC in all.
I usually bump it between 3-4 once or twice and that helps since it is effectively acting like a brake to stop the input shaft from spinning but sometimes even then its still going to grind. Lately I've just come around to shutting off the car if I feel its going to grind but thats very annoying.

Any thoughts on using a Sachs branded clutch kit ? or is it all chinese these days ?

---------- Post added at 12:29 PM ---------- Previous post was at 12:22 PM ----------

I always wondered why this was an issue as well. Going 3rd to reverse has helped reduce it, though that isn't really solving the actual problem.

Its an issue because our transmissions are a cheap as dirt design.
If reverse was fully synchronized and always meshed but not 'engadged' to tranfer power it wouldnt be an issue.

[2.216VTurbo]

2nd to reverse works better for me than 3rd to reverse. I'm in the habit especially when non-TM buds are standing around becuse you can be sure none of thier Range Rovers or Porsches are gonna grind

[shadow88]

Reverse grinds because it's a non synchonized gear. The grinding occurs when the gear is spinning along with the input shaft while the output shaft is stopped. Assuming you're stopped. Selecting any forward gear ( I like 3rd too) stops the input shaft from spinning, thus allowing reverse to be engaged without noise. I haven't driven any manual transmission cars behave differently than yours.

[turbovanman²]

Yep, no synchro's. If its doing what you say, then you have a warped component or its worn unevenly and its catching the driven disc which of course, causes the clash. My 5.0L Mustang was bad for reverse so I would put it into 3rd then reverse, stopped the problem.

Sach's are great, top notch quality.

[Vigo]

My spirit does this. Ultimately its a clutch problem and you have to take the trans out to fix it. It's not normal, it's not right, and shifting to another gear first is just putting the wear on that synchro instead of on the gear teeth for reverse. Sure it's better, but its a hoop you wouldnt have to jump through if things were in good working order.

[cordes]

If the 3rd then reverse trick won't work, something must be keeping the input shaft moving pretty quickly. What that would be I have no idea.

[turbovanman²]

My spirit does this. Ultimately its a clutch problem and you have to take the trans out to fix it. It's not normal, it's not right, and shifting to another gear first is just putting the wear on that synchro instead of on the gear teeth for reverse. Sure it's better, but its a hoop you wouldnt have to jump through if things were in good working order.

Wears the synchro? That's what its designed for. If you wear out a synchro doing that, then the trans isn't strong enough to drive every day,

Some trans are notorious for grinding, no matter what you do, and some clutch's will simply not release enough, so the 1st or 3rd gear tricks are fine, or whatever forward gear makes it easier.

[tryingbe]

I always go 1st then R, never grinds.

[GLHNSLHT2]

My father always told me to go to 1st before reverse to synchronize it so it doesn't grind.

[88C/S]

^^ what they said. Trannys that have "all" gears synchronized can go from neutral into reverse. All others I have used needed a forward gear engaged first before trying to catch reverse. But then again, if the clutch is not releasing cleanly then you're gonna grind reverse.

[135sohc]

Small spline sachs clutch set on order with rockauto.

I just hope I got this 568 put together the right way

[Ondonti]

My Spirit intermittently had this issue before the sprung hub pulled out a rivet.
Using the synchro when you actually have a problem might be okay to get by for awhile but its not a fix. It could be something as simple as needing a washer to space out the cable, or something as serious as faulty components.

If you can't bump 5th (not engage) and drop it into R, then I would definitely be looking into things.

Using a firm aggressive shift helps. It wouldn't grind if you actually got it in. Every time I had a grind it was on a limp wristed shift. Try Old Spice.

[Vigo]

Wears the synchro? That's what its designed for. If you wear out a synchro doing that, then the trans isn't strong enough to drive every day,

If you wear out a synchro doing that it's because you're trying to make the synchro do 15% of the clutch's work because the clutch is only doing 85%. It may be 'common' in some apps but its never 'right'.

Using the synchro when you actually have a problem might be okay to get by for awhile but its not a fix.

[135sohc]

Not saying its 'right' either in this situation, but think of all the load thats happening on the synchronizer assembly during normal driving, thats its job.

[turbovanman²]

If you wear out a synchro doing that it's because you're trying to make the synchro do 15% of the clutch's work because the clutch is only doing 85%. It may be 'common' in some apps but its never 'right'.

Some designs are simply bad designs, it may not be right but who is to say what's wrong and what's right. Is it posted anywhere that its bad to engage a forward gear before reverse? With logic like that, we'd never have figured out how to trick MAP sensors for overboost, as that's, "not right"

Not saying its 'right' either in this situation, but think of all the load thats happening on the synchronizer assembly during normal driving, thats its job.

Exactly and FYI, motorbikes don't have synchronizers, so what does that tell you, Vigo?

[Ondonti]

Its bad because the synchros are designed to slow down the gear stack with 100% clutch disengagement. Using the synchros to slow down the gear stack while the clutch is still engaged means your synchros must cause the clutch to start slipping instead of turning the stack. That is very very hard on them. I would rather do 7k rpm power shifts (fun can be worth some wear).

[Juggy]

I always go 1st then R, never grinds.

+1

make sure you get some load on the clutch as if u were actually going to use the gear....will melt in like butter