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1G Flywheel thickness

XC92

Proven Member
1,190
216
Jul 22, 2020
Queens, New_York
Non-OEM slave might or might not be an issue, but probably the pedal assembly is the biggest culprit. I know it was in mine. When I replaced the clutch and slave it drove fine at first but after a few miles the gears started to grind badly.

Imagine how embarrassing it was to get to Costco to get new tires put in and it was fine till I got there, but when they tried to drive it into a bay they couldn't get it into gear. That's when I realized I had a pedal slop problem. For whatever reason this didn't manifest itself till things warmed up. This was last winter.
 

RLSchwabe

Proven Member
115
22
Mar 21, 2014
Colorado Springs, Colorado
Well, I replaced the leaking SC with an OEM when I replaced the clutch & PP with an SBC kit, just replaced the lower line & hose with SS braided, had a good shop machine the flywheel to the requested step of 0.610 which I verified, and will fix the clutch pedal slop issue soon. I figured that a 1mm shim was thin enough that it wouldn't hurt and might even help since pedal full disengagement is a bit low and the flywheel has lost some metal over several resurfacings.

Given all that you did to fix this, how do you know that the shim contributed to the issues you were having?

I don't know - I suspect that it had to do with the SBC clutch and its geometry. A potential difference in our experience is that my flywheel was brand new ( specs unverified, apparently ACT flywheel are known to be out of spec even new ) and when I had it stepped and resurfaced it was its first time being machined since leaving the factory. In fact, it was Jack's Transmissions that suggested and shimmed the pivot ball after the transmission was rebuilt - and I'm not complaining. I trust Jack's.
 

XC92

Proven Member
1,190
216
Jul 22, 2020
Queens, New_York
Well my flywheel, while stock OEM, has been resurfaced several times so I assume that a ~1mm shim won't hurt and might even help. I also wanted to better distribute the static load of the fulcrum when torqued down, and there was actually an impression of a washer in the trans surrounding the bolt hole so a previous rebuilder put one there, size unknown.

I believe that a resurfacing takes around 0.03" of surface, which is 0.76mm. If this was the flywheel's only resurfacing since I bought the car new then I overshot by ~0.24mm which I assume is meaningless. If it's the second one then it's still short by ~0.52mm, also likely meaningless. If it's the third one (and it's unlikely to be that let alone fourth and beyond), then I probably needed a 2mm shim.

Today I finish putting everything back together and starting the car so I'll find out one way or another. But my gut feeling is that with one or more resurfacings on the flywheel, a ~1mm shim got things back into original alignment, or closer to it.

Btw, what thickness shim do Jack and other reputable rebuilders recommend for a stock AWD flywheel, after each successive resurfacing, or even for a new one?
 
Last edited:

RLSchwabe

Proven Member
115
22
Mar 21, 2014
Colorado Springs, Colorado
Well my flywheel, while stock OEM, has been resurfaced several times so I assume that a ~1mm shim won't hurt and might even help. I also wanted to better distribute the static load of the fulcrum when torqued down, and there was actually an impression of a washer in the trans surrounding the bolt hole so a previous rebuilder put one there, size unknown.

I believe that a resurfacing takes around 0.03" of surface, which is 0.76mm. If this was the flywheel's only resurfacing since I bought the car new then I overshot by ~0.24mm which I assume is meaningless. If it's the second one then it's still short by ~0.52mm, also likely meaningless. If it's the third one (and it's unlikely to be that let alone fourth and beyond), then I probably needed a 2mm shim.

Today I finish putting everything back together and starting the car so I'll find out one way or another. But my gut feeling is that with one or more resurfacings on the flywheel, a ~1mm shim got things back into original alignment, or closer to it.

Btw, what thickness shim do Jack and other reputable rebuilders recommend for a stock AWD flywheel, after each successive resurfacing, or even for a new one?


I don't recall what size shim(s) they used or how many. I simply don't trust my memory as they rebuilt it in the Spring of 2019
 

1990dsmkid

Proven Member
612
54
Jun 14, 2012
Bellwood, Pennsylvania
So i know its been awhile but i finally got a chance to pull out assembly. I had already ordered a rebuild kit from RTM Racing. After getting it out and tearing it apart i found no wear or excess play. So i installed back together with brass bushing and factory lever. Ill keep new lever for future. I tightened it up nice and snug. Im going to weld it and reinstall. If i still have the same pedal pressure then im left with either still air in system or the pressure plate is just that shitty. I might even just go ahead and order new clutch and check flywheel step this time and go from there. Either way its gunna take me some time. Just wanted to post an update
 

Mech Addict

Supporting Member
716
271
Jun 9, 2019
Jackson, Wyoming
was there NO play at all between the end of the clutch shaft and the separate clutch lever (with the hole that has only two flat sides, instead of six). Mine had very little, but enough to tell there was just a scoshe clearance in there, yet when it was all installed, there was a significant amount of slop in the clutch pedal. It wasn't even wear on the hole in the level, it was just a tiny amount of squish on the flats of the clutch shaft end.

Once you weld it, it should never have any play. Make sure the weld is done well, because I've seen a few posts about folks who's welds kept failing on these. I'm no welder, so not sure what to tell you. If you're not either, get someone who knows.

Good luck
 

1990dsmkid

Proven Member
612
54
Jun 14, 2012
Bellwood, Pennsylvania
To me i dont notice any play. Neither part looked worn either. Even if this isnt the problem at least it wont become one later on after its welded
 

1990dsmkid

Proven Member
612
54
Jun 14, 2012
Bellwood, Pennsylvania
Alright so another update. I finally got time to put it back together. I gravity bleed slave cylinder just because then went for a drive. Besides not liking the puck disk and the pedal seeming to soft but it might not be. Havnt driven dsm in years so could just be me. Everything seems alright except shifting into 3td has to be slow and easy and the one time i tried downshifting into 3rd it was bad. Also one time as stop it grinded a little trying to go into 1st. So im still not sure if im having a clutch/hydraulic system issue or is the sycros are just shot. What do you guys think? Thanks
 

XC92

Proven Member
1,190
216
Jul 22, 2020
Queens, New_York
If there's no excessive play but with 1" or more before the clutch starts to disengage and then after it fully disengages, and you're sure that the master and slave are fine, the master rod is properly adjusted, the lines and hoses are fine, the clutch and PP are OK, the flywheel is fine and was properly machined when the clutch was replaced, the throwout bearing, fork and fulcrum are good, the mounts are good, the trans is fully and properly bolted to the engine, the shifter, cables and connections are fine, and you bled the system properly, then I don't see what else cause be causing this other than the trans internals, and you'll have to drop it and open it up to find out.
 

1990dsmkid

Proven Member
612
54
Jun 14, 2012
Bellwood, Pennsylvania
Im gunna try not to drive it unless i have to and when i do i will baby it. Hopefully i can make itll spring and just get new clutch and flywheel and see about trans rebuild or another trans
 

Mech Addict

Supporting Member
716
271
Jun 9, 2019
Jackson, Wyoming
Have you tried the test for a dragging clutch? It’s well described on this site somewhere and also on the Jack’s Transmissions FAQs. Basically just push in the clutch with the trans in gear, rev way up and see if the car tries to creep. That will indicate the clutch isn’t fully disengaged when the pedal is pressed. Makes shifting difficult and wears out rapidly, kills synchros, etc. But you also might just have worn out synchros. Either way, if you drive sparingly and gently it shouldn’t grenade too quickly.
I pulled my trans today, in my mostly unheated garage. Not waiting until spring, which around here comes mid May!
 

XC92

Proven Member
1,190
216
Jul 22, 2020
Queens, New_York
Im gunna try not to drive it unless i have to and when i do i will baby it. Hopefully i can make itll spring and just get new clutch and flywheel and see about trans rebuild or another trans
Second on Mech Addict's advice. I was in a similar situation as yours last year. I had multiple overlapping and in some cases cascading issues with my 1G DSM, some of which I wasn't even aware of at the time.

Clutch all worn out, bad slave, all 4 calipers seized because it sat outside for several years, tons of rust making it hard to see what was wrong, manual trans kept popping out of first (before the clutch wore out), other issues.

I dropped the trans to replace the clutch and hopefully also fix the trans issue, but it got too cold and I had to move the car for other reasons before I was able to fix the trans but I did replace the clutch and slave before I put the trans back on.

When I did it soon became apparent what was likely going on. The clutch pedal had developed that infamous 1G slop, so the clutch didn't fully disengage, which wore down the 1-2 dogteeth, sleeve and synchros, and likely also prematurely wore down the clutch.

I managed to temporarily fix the pedal slop issue by tightening down the shaft bolt (eventually I'll have to pull the assembly and get it welded, but it's help up so far), but the popping out of 1st issue would have to wait till spring. Meanwhile I drove it as little as possible and very carefully.

It held up, and late June I was finally able to drop the trans again and fix the issue (I'd wanted to get to it earlier but my mom's car needed a lot of work). Basically rebuilt the whole thing, replacing the 1-2 hub/sleeve, 1-4 synchros, springs and keys, 3 of 4 bearings, few other parts, and dressed some gear teeth that had rounded or chipped.

Never did it before so I took my time, asked a lot of questions, annoyed a lot of people here, and ordering and waiting for parts took a while. I was thorough and knew each part by heart before I was done. But I fixed the issue and the car's been fine since, no popping, no grinding, mostly smooth shifts (to the extent possible with this trans).

Basically, sounds like you have multiple issues and until you solve all of them you won't be out of the woods. But you can probably drive it carefully until you're able to resolve them all. Just use common sense. Good luck.
 

XC92

Proven Member
1,190
216
Jul 22, 2020
Queens, New_York
Have you tried the test for a dragging clutch? It’s well described on this site somewhere and also on the Jack’s Transmissions FAQs. Basically just push in the clutch with the trans in gear, rev way up and see if the car tries to creep. That will indicate the clutch isn’t fully disengaged when the pedal is pressed. Makes shifting difficult and wears out rapidly, kills synchros, etc. But you also might just have worn out synchros. Either way, if you drive sparingly and gently it shouldn’t grenade too quickly.
I pulled my trans today, in my mostly unheated garage. Not waiting until spring, which around here comes mid May!
Kudos on pulling the trans. I forgot, what's the issue with it? And yep, working on a car in cold weather is a real pain. Numb hands, hard to manipulate tools and parts, everything takes much longer. I'll only do what absolutely needs done once it gets much below 50. I had to rush a timing belt and water pump job on 3 different cars this month so I could refill the coolant and not have the engines rust or bust. Just barely made it before the first frost hit. Still have a bunch of work on all three but it'll mostly have to wait till March or April. Good luck with your work.
 

1990dsmkid

Proven Member
612
54
Jun 14, 2012
Bellwood, Pennsylvania
No slop in my pedal assembly. Im going to to the drag test today. If it is dragging im kinda screwed. I dont have a lot of threads left to adjust pedal. That is part of why i started this thread. I thought maybe flywheel was cut beyond its limits. Ill post back later today what i figure out today. If trans needs rebuilt ill have to find someone to do it. I dont really have time for that and i tried rebuilding a trans somewhat before. Yea its not for me
 
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