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Old 04-20-2018, 03:49 PM   #1
oemoilleaks
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Default m40 transmission grinding when shifting into Reverse

Hello all,

I just finished replacing the clutch and resurfacing the flywheel on my 142s.

As per Eric @hiperfauto's suggestion I had the flywheel surfaced and then did a reverse step of 0.020" outside the clamping area.

With the flywheel surfaced and the new clutch, pressure plate, and throw out bearing in I went to move the car for the first time. As soon as I motioned toward reverse I had a horrible grinding. I shifted to first then reverse.. still grinding. Tried second, third, and fourth before reverse and it always grinds going into reverse.

It never grinds going into any other gear.

I then moved on to the clutch cable, which has a 1/4" collar on the ball end and is adjusted to the end of it's adjustment area. No matter what I did, it still grinds getting into reverse.

I'm kind of at a loss for what it could be. Any suggestions?
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Old 04-20-2018, 04:00 PM   #2
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There's no syncro on reverse, the gears (and clutch disc) have to have stopped turning when you try to shift into it or it will grind to some degree.

Sometimes, the clutch disc is just still spinning when you let the clutch out, but if you put it into another gear, like you did, that would stop things, and then shouldn't grind.

If it does grind after that, it means that something in the clutch area is dragging enough to spin the clutch disc/input shaft up again as soon as it comes out of the other gear.

Various possibilities:
- clutch adjustment - not opening far enough to completely release (when driving, does the clutch release with the pedal down close to the floor?)
- clutch disc installed backward - from what I hear this can allow the center section to lightly drag on the flywheel
- clutch disc sticking on the input shaft - when the pressure plate releases, the clutch disc doesn't move easily on the input shaft and remains lightly pressed against the flywheel
- stiff/hanging pilot bearing - that needs to freely spin when the clutch is released
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Old 04-20-2018, 04:09 PM   #3
oemoilleaks
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Quote:
Originally Posted by JohnMc View Post

Various possibilities:
1. clutch adjustment - not opening far enough to completely release (when driving, does the clutch release with the pedal down close to the floor?)
2. clutch disc installed backward - from what I hear this can allow the center section to lightly drag on the flywheel
3. clutch disc sticking on the input shaft - when the pressure plate releases, the clutch disc doesn't move easily on the input shaft and remains lightly pressed against the flywheel
4. stiff/hanging pilot bearing - that needs to freely spin when the clutch is released
Hey John,
Below are the answers to your queries.

1. That seems to be the leading theory. The clutch releases about halfway through the throw, and the pedal, when fully pushed in, is an inch above the floor.

2. I'm pretty sure I put the side that said "toward flywheel" toward the flywheel, but maybe I didn't. This picture isn't high res enough to tell, but after typing "ENHANCE" a bunch of times on the keyboard in photoshop I was able to see it says "GEARBOX SIDE"



3. I greased the splines slightly to prevent binding. Not sure if that would help or hurt.

4. I checked the pilot bearing and it spun like new. Literally compared it to a new one I was going to put in.

Last edited by oemoilleaks; 04-20-2018 at 04:59 PM..
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Old 04-20-2018, 04:12 PM   #4
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#1 is the most common issue, and the easiest to fix (don't have to pull the trans).

The clutch release point doesn't sound so bad, though, but perhaps try to adjust it upward in the pedal travel some to see if it helps?
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Old 04-20-2018, 04:24 PM   #5
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#1 is the most common issue, and the easiest to fix (don't have to pull the trans).

The clutch release point doesn't sound so bad, though, but perhaps try to adjust it upward in the pedal travel some to see if it helps?
I did. the engagement point is really high and I'm actually out of adjustment threads on the clutch cable.

Everyone keeps saying stack washers, but given the way the clutch cable is engineered I'm not sure where to stack said washers.
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Old 04-20-2018, 04:28 PM   #6
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FWIW I've never seen a B18/B20 flywheel with a stepped face on it - the pressure plates are (AFAIK) designed to sit on a flat surface with the clutch disc. But I'm sure Eric/Hiperf knows a ****-ton more about it than I do.
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Old 04-20-2018, 04:38 PM   #7
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Are you sure you used the correct throw out bearing?
My foggy memory seems to think that there may have been two different sizes.

Is the clutch cable tight to the firewall?
I think later clutch cables need to be shimmed or have some kind of washer up against the firewall to take up some slack.
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Old 04-20-2018, 04:56 PM   #8
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Are you sure you used the correct throw out bearing?
My foggy memory seems to think that there may have been two different sizes.

Is the clutch cable tight to the firewall?
I think later clutch cables need to be shimmed or have some kind of washer up against the firewall to take up some slack.
There is a washer up against the firewall. And a collar at the ball.. I went outside and took a photo of the setup, annotated it, and uploaded it so everyone could see what I'm dealing with.

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Old 04-20-2018, 05:16 PM   #9
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Check the cable at the pedal to make sure it isn't stretching/fraying.
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Old 04-20-2018, 05:28 PM   #10
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Quote:
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Check the cable at the pedal to make sure it isn't stretching/fraying.
****, I drove by at 9 to see if y'all could take a look at it. ;) Still can before I head home from work. I'm a literal mile away from y'all and the lower dash panel is already off.
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Old 04-20-2018, 05:37 PM   #11
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We're here till 6. Come on by.
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Old 04-20-2018, 05:51 PM   #12
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We're here till 6. Come on by.
For sure will!
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Old 04-20-2018, 07:45 PM   #13
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Well as usual the boys from HiPerfAuto solved it.

Just got back from paying Ian and Eric a visit. Ian took about 2 minutes to figure out that the clutch fork is bottoming out on the bell housing and that I need to put some shims under the pivot ball.

Unfortunately, I won't get to that before this rally I have next week. So I'll update once I do it.

Now on to gaining the confidence to rebuild the brake booster and install a new master cylinder!
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Old 04-20-2018, 10:40 PM   #14
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Quote:
Originally Posted by JohnMc View Post
FWIW I've never seen a B18/B20 flywheel with a stepped face on it - the pressure plates are (AFAIK) designed to sit on a flat surface with the clutch disc. But I'm sure Eric/Hiperf knows a ****-ton more about it than I do.

+1 on that. Can we get an explanation? A little more clamping force maybe?

It moved the pressure plate away from the fork, and now you will be shimming the fork toward the PP.
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Old 04-21-2018, 06:58 PM   #15
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Even though the Volvo green books don't mention a step, just about every 6 bolt flywheel I have ever pulled had a step.

The machinist I have been using for over 30 years has always put a step on my 6 bolt flywheels.

I've searched the internet and found pictures of Volvo 6 bolt flywheels with and without steps.

Evidence against a step is a picture of a NOS flywheel that VP has for sale and it appears to NOT have a step.

However, the 1 picture of a flywheel being surfaced in the Volvo green books, appears to have a step.

The step increases clamping pressure and at .020",it isn't a major modification.
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Old 04-21-2018, 11:20 PM   #16
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Well I guess that covers it.
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Old 04-23-2018, 03:50 PM   #17
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