77' M4 Sachs clutch

Travis /
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ok, so after multiple hours of work on my M4 I've got her running 100% My last hurdle was a drive clutch that was engaged all of the time, The first thing i did was read all of the post regarding Sachs clutch work, I extracted a bunch of good information before removing the 17mm nut that holds the stack in place..(i even learned the proper terminology) After building up enough confidence to start disassembling the clutch I began..


1. Place a catch pan under the clutch cover to catch the 1/2 quart of ATF fluid you just poured in there...hahaaha

1. Remove the 5 flathead screws holding the clutch cover on and let it drain into your catch pan.

3. Loosen the long flathead screw the runs North and South through the clutch case that holds your clutch arm in place. There is a spring that is on the lower portion of the screw that is under tension, I used a small flathead screw driver to flip the lower end up and out of its position before completely removing the long screw. Pay attention to the stack-up of the components as there is a bushing, copper washer clutch arm and spring all on this long screw.

4.Remove the "cup" that is now exposed in the center of your clutch stack.

5. Remove the flywheel cover on the opposite side of the engine(chrome cover that says SACHS).

6.Use a 14mm socket to hold the nut/engine from spinning and place a 17mm socket on your nut holding the clutch stack in place.

7. Hopefully your clutch side nut cracks loose and not your flywheel side..lol..

8.Remove the nut, semi square washer and thin large shim and your first clutch plate.There is a wavy spring washer between each complete stack of plate and disc's(see drawing for reference)

Now here is where I discovered my problem..My first clutch plate was 'welded' to the clutch disc(fiber disc)..or rusted,corroded..ect. Probably from sitting in a damp basement for the last 15yrs.Upon this discovery I decided to remove all of the plates/discs to inspect and in doing so I found that all were stuck together. I scraped most of the rust/junk off of the steel plates and then sanded each on smooth with 220 grit sandpaper. I also inspected and scraped each disc(fiber disc) to ensure that they made even contact with the plates when engaged.

9.After to remove all of the plates/discs you'll find a weird looking donut shaped thing..That's your centrifical clutch's brain..It should be clean and stretchy like a bracelet, How it works is pretty cool for those of us who haven't really played with this shit before..Once your engine hits 2200rpms the donut expands grabbing your outer basket(whats left after removing all of your discs/plates/washers and a center gear) making your entire clutch/clutch basket one..then driving your front sprocket.

10. Once you have everything cleaned to your liking put it back together the same way you took it apart(or follow the drawing)


11.Make sure your first plate is fully seated on the center gear, if it isn't you will just grind all of your teeth off of the plate or the gear..BAD,BAD thing to happen, lucky for me,,after I eff'd mine up it had just marred a few of the teeth so my Dremel tool came in handy grinding down my plate back to where it fit on the center gear...lol(wheew)

12.Once your stack is complete, put your large thin washer/shim, semi-square washer and nut back on centered over your center gear(important or else your clutch stack will always be engaged once you tighten your 17mm nut)and tighten it down nice and firmly while holding your flywheel nut(14mm) still with another wrench/socket.

I read some entries on here that stated the nut tightening is critical..but its nut, I reefed the shit out of mine after it had spun loose twice on me..as long as your wavy spring washers are still good,your center gear is IN not on(like what happened to me) your first clutch plate then you cant over tighten it...unless you strip the fucker..lol...common sense needed. Oh, and dont forget to put in that little cup thing like I did 9 effing times! Anyway, once its all back together try spinning your back tire..as long as your clutch discs are wet with ATF fluid your clutch should slip now..as in your engine shouldn't turn over when spinning your rear tire..If your clutch is dry then it probably wont slip for ya..try squirting some fluid on/in there and then spin the tire while holding your 17mm nut still with your socket..That should by all rights work if you've put everything back correctly.

13.Start putting your clutch arm back together..remember your bushing/brass washer position? If not refer to drawing..lol Now just use a flat head screw driver to pop your spring back into position.

14.Now setting up your start/engine engage set screw..loosen the 10mm nut and back the brass screw out until you see a gap between it and the "cup" in the center of your clutch stack

then run it back in until it just touches the cup, then grab your decomp lever and spin your back tire...Does your engine turn over???If so your good to go..If not run the brass screw in a little more..keep going until spinning your rear tire turns the engine over when the decomp. lever is pulled.Dont forget to tighten the 10mm jam nut once your happy with the set-up.

15.Put your clutch case cover back on and fill your tranny back up with ATF fluid..

I hope this was helpful to anyone who needs it..I sure learned a lot while tinkering with my ped, thanks to all for your advice.


1977 Hercules M4

This single post is part of a larger thread. Start from the top or view this post in context.
Subject Written By Posted
  77' M4 Sachs clutchTopic by: Travis Travis 03/18/09 03:22PM
  Re: 77' M4 Sachs clutchRe: ethanol ethanol 07/02/09 12:03PM
  Re: 77' M4 Sachs clutchRe: Travis Travis 07/02/09 01:55PM

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