Transmission overhaul manual

[Scubasteve762]

Does anybody know the part number and or source for the overhaul manual for the 4 speed manual transmission, should be the G72. The manual should be called “Clutches and Transmission” or something like that.

[Benz Dr.]

I've done a number of 4 speed boxes for 113's and 190SL's. Nothing overtly difficult but special tools sure do help. I'm actually using a Glen's workshop manual from the 60's to get the specs needed. One thing I often find is the input shaft won't have the correct end play and is often .020 - .030'' more than is required. This shaft should have next to zero end play and will result is less that crisp shifting if not set up properly.
 It takes about a day or more to do one and should include a new seal kit and new bearings. New syncro rings are not a bad idea but not always needed. A special tool is required to install the input shaft seal ( don't bother replacing it if you don't have this tool ) and the slotted main shaft nuts require a special socket. The speedo drive seal should be replaced and can be carefully drilled out after removing the shaft and gear which is a press fit. You will need a depth micrometer to make some crucial measurements and a whole lot of shims to set the end play.

[Jonny B]

Note that in Pagoda Notes Vol 3 issues 1 & 2 (available to full members, one of a number of good reasons to spend the entry fee) there are a a nice lot of photos and directions from one of our members that overhauled his manual transmission.

[Peter van Es]

And these issues can be downloaded here: https://www.sl113.org/wiki/Restricted/PagodaNotes

[Shvegel]

This book has a really good chapter on rebuilding the trans:

https://www.amazon.com/Glenns-Mercedes-Benz-Repair-Tune-Up-Guide/dp/1869826329/ref=sr_1_fkmrnull_1?keywords=Glenn%27s+mercedes+benz+repair+and+tune+up+guide&qid=1550455046&s=gateway&sr=8-1-fkmrnull

If you are rebuilding for cause and you do not have a lot of manual transmission experience at the very least have someone with experience look over your parts.  Sometimes knowing where to look is the difference between doing it once or getting it back together and having it still pop out of gear.  I have some of the tools like the pin sockets and the puller for the layshaft bearings etc.  More than happy to lend them out.

[Shvegel]

Just realized Dan recommended the Glenn's manual as well.  Great photos of a guy in greasy coveralls and battered hands making it happen.

[Benz Dr.]

Just realized Dan recommended the Glenn's manual as well.  Great photos of a guy in greasy coveralls and battered hands making it happen.

I've been using that manual for over 40 years. Actually a pretty good read.

[RoyB]

I am in the process of going through my 4 speed manual transmission as well.  I read this thread, and immediately purchased Glenn's Mercedes-Benz Repair/Tune-Up Guide along with downloading the Pagoda 3.1 and 3.2 Newsletters.  However, until the book arrives, I am stuck.  The transmission is out of the car and on the bench.  I am trying to remove the Bell housing, but something is holding this together that I cannot see.  The 4 large bolts connecting the transmission tot he Bell housing are out, as are the 6 smaller bolts.  The Throw Out Bearing Fork seems to be attached to something inside, so that is still in place.  I can rotate the bell housing on the transmission shaft, but can only pull the bell housing away from the transmission about 3/16 of an inch.  Is there a circlip inside of the transmission that I need to access from the top cover?  What am I missing here?  Thanks

[Benz Dr.]

I think there's a ball under the throw out fork that's threaded into the main case of the trans. You will likely need to remove it.

[RoyB]

I gently tried to pry the fork away from the mount or stud, but I was not able to detect any movement.
I can rotate the bell housing 360 degrees on the input shaft, so the stud for the fork is not going into the transmission case.
If I know that the fork will separate from the stud I can apply more leverage, but hate to do so without knowing the proper process.
On another note, I am trying to source the spanner tool used for the back of the transmission.
In the Erratic Speedometer section, there is a home made tool made from a 1.125 socket and a die grinder.
I can make one of the those, but would also like to see if this can still be purchased, borrowed or rented from one of the group.
A constant puddle under the car caused by a leak where the transmission bolts to the bell housing, rattling and rumbling of gears when coasting, as well as the erratic speedometer are the main reasons for the disassembly.
Thanks

[Benz Dr.]

There's a circlip on the throw out fork and you will need to use a bit of force to make the fork pop off of the ball stud. Use a hooked bar or similar.

Sounds like your trans has more than just a few problems. Worse one I ever saw was when a bearing went bad and the gears tried to climb resulting in a split case from end to end. Odd thing to me was, wouldn't you hear all of that noise long before it blew up?

[RoyB]

Thanks for the additional information.
I will try to put a support or brace behind the other side of the fork so when I try to pry it off with a Wonder Bar, it should come off straight.
With the rumbling and rattling, I suspect this transmission was run dry more than once.
I filled it when I bought it, and have continued to fill it while resolving other issues.
After this issue is resolved, it is on to the steering box which leaks, then the differential which also leaks.
Each of these projects seem to get larger in scale.

[ja17]

There is one large woodruff key in the lower gear cluster which is often broken or worn.  In addition there is another woodroof key in the upper gear cluster which is often damaged. Be sure to check these. Pat is correct, the Glenn's manual is a good source. Its written so the average amateur can understand it.

[RoyB]

Thanks Joe.  Per Dr. Benz suggestion, I put a 3/8 extension between the front of the throw out fork and used a rubber hammer to tap the fork from the outside of the bell housing.  After a few taps, the bell housing separated, but the fork remained in place.  I tapped on the fork mount to ensure it was not partially loose, and everything appears proper.
The suggested book is on its way, so I will study that when it arrives then begin the teardown.  If anyone can rent / loan me the special spanner to remove the bracket on the tail shaft, I would appreciate it.  Otherwise I will create one per the Erratic Speedo section prior to the disassembly.
As always, thanks to the group for assistance.  Despite having 6 repair / service manual related books on this car, soon to be seven, this forum has guided me through the repairs needed on this 230SL.

[Benz Dr.]

The input shaft seal is another animal and you will need a special tool to install it. DON'T remove the old seal unless you have an installation fixture. I made my own on a lathe and that could be a solution for you. If you can't put this installation together leave the old seal in place.

The front input shaft is supposed to have zero end play but often has a lot more than that. I'm not sure why that is, but it would seem like there's a shim missing in the assembly of every one I've ever had apart. Generally, it takes about .030 - .050'' of shim thickness to sort this out. You will need a depth micrometer to figure out how many shims to use and then you will need to find those shims in order to do this right. ( and you expected this to be easy, eh? )

The speedo drive seal should be replaced. I drill it out carefully and remove the metal ring left over from the old seal. There is a slight shoulder in the hole for the seal to press up against and it should be installed up to that point. You will need to remove the shaft that drives the speedo cable first.

There's a lot more to doing a rebuild than this but this will get you started.     

[RoyB]

I read about the need for the special tool, and see what it would seem to take to install that seal.
Reading into your comment regarding the end play, I would need to measure the depth of the recess on the bell housing with the depth micrometer, then subtract the distance from the outer edge of the bearing to the circlip and subtract the two in order to determine the required thickness.  I have two shims in there now, adding up to a total of .015.  A far cry from the .030 to .050 you are referring to.  Where do I order these shims?  Would my local MB dealer be able to order those?  Could I also get the special spanner tool for the output flange on the tail-shaft there as well?  I have searched the internet without success for that tool.

[Benz Dr.]

I read about the need for the special tool, and see what it would seem to take to install that seal.
Reading into your comment regarding the end play, I would need to measure the depth of the recess on the bell housing with the depth micrometer, then subtract the distance from the outer edge of the bearing to the circlip and subtract the two in order to determine the required thickness.  I have two shims in there now, adding up to a total of .015.  A far cry from the .030 to .050 you are referring to.  Where do I order these shims?  Would my local MB dealer be able to order those?  Could I also get the special spanner tool for the output flange on the tail-shaft there as well?  I have searched the internet without success for that tool.

Yeah, I'm sort of guessing how many shims you would need. I think you can get them from MB but I've also made them myself using sheet metal for the thicker ones. Not a fun job but it's what I did to get it closer into spec. We made our own pin socket from an old thin walled socket and it works OK - not great but good enough.
You have the right idea about how to measure the end play and determine shims required. It's not that hard to install new bearings and a couple other parts and still have a working unit when done. Getting all of the fine detail right is the fun challenge. I'm still working on that.

[RoyB]

Thanks again for your feedback.  I will keep the group posted on my progress.

[RoyB]

All

I am on hold again while I wait for parts, tools, etc.  In the meantime, I have also decided to help an old friend with one of his older friends and assist in trying to get a 1964 300SE running again after sitting in the garage for 15 plus years.  More special tools required for that project as well:)
In reading the Glens Repair manual for seemingly the 100th time, I continue to see the use of an assembly that holds first and second gear together on the main shaft. This is recommended while a Slotted Spanner Nut is used to remove the nut in order to access the speedometer housing. Is this pinching type of tool required or just nice to have if you are not cautious? 
Is there anything else I need to be aware of during teardown or assembly?  This group is full of special processes and thoughts, so once again I request your indulgence and I work my way through these things.  I remember seeing a post from JA17 regarding a hose clamp on the roller bearings behind the front main shaft bearing, but I do not recall where that post was from. 
As always, thanks again for your help.  I know I could not do this without the support of this group.  12 service and repair manuals and 100 plus more questions - and counting. Who knew that I could have this much fun:-/

[Benz Dr.]

You need the pin socket for the rear nut and the special tool to install the input shaft seal. Everything else is pretty much regular tools. Oh, use thread sealer on all of the screws or you will have leaks.