Transmision does not shift beyond 2nd gear & no sppedometer reading

[MBman]

Could anybody advice…
My 68 280sl with automatic transmission (GA 280SL) does not change into to 3rd or 4th gear and the speedometer is not working either. I read in service manual that two things could be wrong. 1- Regulator pump not driven (How can I test) and 2- Worm gear drive of regulator is defective.  Is there any test or fix I can do before I need to remove the transmission?  It looks like there is a cover that could be removed to get to the speedometer. Appreciate any advice.

[stickandrudderman]

It's pretty much inevitable that you're in for a full transmission o/haul.

[ja17]

Hello MBman,

First determine if the speedometer malfunction is originating from the transmission. Do this by making sure the cable is not broken. If it is not broken and it is not turning then the malfunction is at the tranmission.  Make sure your trans fluid is at the correct level. 

Next remove the tranmission metal cover plate under the car. This is the heavy plate with all the 17mm bolts. some of these bolts will be a challenge since they are above the exhaust.   

Your goal is to check the rear slotted nut on the transmission flange. If this nut came loose it can cause the speedometer not to function and it will eventually cause all kind of serious transmission problems. 

Remove the rear transmission mount and bracket then remove the six tranmission/driveshaft bolts will. The slip joint on the driveshaft must be loosened so it can be moved back out of the way.  Nested in the rear transmission flange is the slotted nut. It must be tight.

Get back with us if you get this far for more options.

[MBman]

Thanks guys.  I did check the fluid and it was on the upper level line when the engine was hot (changed the transmission oil and filter 30 miles ago).
I will start working on it tommarow and try to check the rear slotted nut on the transmission flange. how much work it is to R&R the transmission don't have lift but done lots of work on the ground. 

[69280sl]

Complete trans overhaul may not be inevitable. I had exactly the same symptoms on my car, also a 1968. I was quoted about $700 to take care of the problem which was in the backend of the trans so R&R would not have been necessary. I opted for an overhaul instead at about $2600. The book time for R&R is about 8 hours if I recall correctly.

Gus

[ja17]

Hello,

Once you get the driveshaft disconnected your 1/3 of the wqy toward removal.  Always remove the six torque converter/flywheel bolts  before removing the transmission or you will ruin the front pump.   

Some Mercedes Finback and W108 six cylinder gas sedans of the era used the same transmissions.

Keep us up to date.

[MBman]

Thanks for all the help.
I managed to get to the slotted nut on the three legged flange; it had the ring nut nicely done so I don’t think it was loose, could not feel any play and no oil leak from the rear seal. After unlocking the locking ring I was able to turn the nut with couple of slight chisel hits (How tight does this nut need to be in order to cause problem??).  At this point is there any other thing I can try or test that I can do before preceding to transmission removal?
Thinking ahead… any recommendations on where I can have the transmission rebuilt with reasonable price?
Thanks

[MBman]

Thanks for all the help.
I managed to get to the slotted nut on the three legged flange; it had the ring nut nicely done so I don’t think it was loose, could not feel any play and no oil leak from the rear seal. After unlocking the locking ring I was able to turn the nut with couple of slight chisel hits (How tight does this nut need to be in order to cause problem??).  At this point is there any other thing I can try or test that I can do before preceding to transmission removal?
Thinking ahead… any recommendations on where I can have the transmission rebuilt with reasonable price?
Thanks

[merc67osl]

Hello,
I had the same problem with my 250 SL (and others in this forum before me).  Turned out a locking pin in the rear of the transmission was the problem.  Thanks to the BBB, parts from a donor transmission, a helping hand and a nice weekend everything went fine.     

The repair in my case consisted of removal, replacement and installation of the Rear Transmission Housing with centrifugal governor (see BBB 27-8).  You can do the repair with the transmission in the car.  The exact procedure can be found in 27-28 ("Rear Transmission Housing and Centrifugal Governor").  It is important not to deviate from this.  After removing the back cover, look for the locking pin inside.  Check it and if its groove both are in proper condition (not that easy to find, try first BBB figure 27-28/11 and look for item no. 35b). 

My locking pin had done the impossible: turned itself 90 degrees and somehow lodged itself tangentially to the axle/output shaft (with the slot nut) rather than perpendicularly as by design.  The pin itself was slightly damaged (flattended), as was its boring/groove (a bit disfigured). 

How could this happen in the first place?  An indication of something suspicious could actually be seen from the outside of the rear transmission housing. The distance between the three legged flange and the housing seemed wrong. The telltale was that the bolts and the flange area around the bolts showed wear (which I had not noticed before).  Someone must have ignored to apply the correct torque wrench settings which had resulted in components gradually working themselves out of position.  Which made sufficient room for the locking pin inside the rear transmission housing to turn on itself.  Which again made the governor standing still on the axle.  No movement from the governor, no hydraulic pressure to bring the transmission from 2.nd to 3.rd or 4.th gear and no movement of the speedometer as well.

It´s probably worth a try before pulling out your transmission for a total rebuild. 
Keep us posted


   
                           

               

[J. Huber]

Merc67 Oslo's idea is worth a look for sure. If you need to go to a rebuild - I think this outfit is our most recommended choice. No experience (thank Goodness)...but heard good things.

http://www.mercedesdismantlers.com

[drmb]

I have repaired this problem before, the drive gears in the rear housing that drive the secondary pump and governor strip so ther is no drive for these components this also drives the speedo. The primary pump at the front of the transmission will only get the  car moving in 2nd gear then the output shaft of the transmission turns and also drives the rear pump and governor but this is not happening because of the drive gear failure.Good luck.

[MBman]

Thanks drmb
You are correct… Today I opened the backside of the transmission and got the governor assembly out and found that the Drive Sleeve on the secondary pump was striped. This is the ½ inch tube like sleeve that connects the secondary oil pump to the warm gear drive shaft with inside fine slots. The striped side was the driving oil pump side, so the secondary oil pump was not turning and as you said no 3rd or 4th gear The question I have now is do I have to replace the pump gears they look O.K but they must of got stock at some point that the sleeve got striped. I worry about if this will happen again. Can I buy the whole pump section or just the gears also where did you end up buying your parts. does the Mercedes dealers carry them.
Thanks for your help

[MBman]

Thanks James, Looks like I found the sorce of my problem. Now if I can get the parts and put everything back correctly I might not need a rebuilt tramsmision, But if I do I will try your source.

[felipealonso]

Hello MBman,

First determine if the speedometer malfunction is originating from the transmission. Do this by making sure the cable is not broken. If it is not broken and it is not turning then the malfunction is at the tranmission.  Make sure your trans fluid is at the correct level.  

Next remove the tranmission metal cover plate under the car. This is the heavy plate with all the 17mm bolts. some of these bolts will be a challenge since they are above the exhaust.  

Your goal is to check the rear slotted nut on the transmission flange. If this nut came loose it can cause the speedometer not to function and it will eventually cause all kind of serious transmission problems.  

Remove the rear transmission mount and bracket then remove the six tranmission/driveshaft bolts will. The slip joint on the driveshaft must be loosened so it can be moved back out of the way.  Nested in the rear transmission flange is the slotted nut. It must be tight.

Get back with us if you get this far for more options.

This makes sense the speedometer is connected properly to the tranny, regarding the tranny shifting to the higher gears I guess you need to put some labor cost to it and check it to your nearest mechanic.

Motor and Transmission Mount Bracket

[jacovdw]

What does a link pointing to Nissan/Hyundai transmission mounting brackets have to do with pagodas...   

[W113SL]

MB Man:  I have a complete used transmission for 1968 2.8 engine.  If you wish to take a chance on a used trans, let me know.  It came out of a 1968 300SEL 2.8 and was running Ok when it was removed.  I prefer to send the entire trans rather than disassembling it.  Where are you located?  I am in Northeast Ohio.

W113SL