SL/R230: Transmission slip and limp mode
02-04-2017, 09:28 AM
#1
Junior Member
Thread Starter
Transmission slip and limp mode
Two weeks ago my 7-speed transmission slipped out of gear at a stop light. After I waved everybody by, I put the car in Park and back in Drive and all seemed well. When I got home, I searched the Internet for information.
Several days ago this happened again, but this time it only helped for a few blocks before it slipped out of gear again. Then there was a serious clunk and I landed in limp mode (2nd gear). I drove 11 miles on US1 at rush hour at 25 miles an hour. I parked in my garage. One forum suggested that low tranny fluid might be the problem. I ordered a tranny dipstick and fluid which arrived today.
Now I find that my 722.9 transmission has no way to check or add fluid. Without having my SL taken to the dealer, what can I do?
Several days ago this happened again, but this time it only helped for a few blocks before it slipped out of gear again. Then there was a serious clunk and I landed in limp mode (2nd gear). I drove 11 miles on US1 at rush hour at 25 miles an hour. I parked in my garage. One forum suggested that low tranny fluid might be the problem. I ordered a tranny dipstick and fluid which arrived today.
Now I find that my 722.9 transmission has no way to check or add fluid. Without having my SL taken to the dealer, what can I do?
02-04-2017, 01:06 PM
#2
There seems some great info here
https://mbworld.org/forums/c-class-w...ce-thread.html
I would suggest first action would be get fault codes read, especially if you hit limp mode it will have recognised a fault.
https://mbworld.org/forums/c-class-w...ce-thread.html
I would suggest first action would be get fault codes read, especially if you hit limp mode it will have recognised a fault.
Last edited by Essell55mb; 02-04-2017 at 01:41 PM. Reason: URL link fixed
02-04-2017, 01:20 PM
#3
MBworld Guru
I also answered of on benzworld:
As you discovered, the 722.9 has no dipstick or even a dip tube. It is checked from underneath by removing the drain plug and observing the flow rate at a specific fluid temperature. Your problem could be low fluid, but it could be other problems. I'd get a proper diagnosis with a scan tool that can read MBZ-proprietary DTCs from the TCU.
If you want to check the fluid level, you can. First of all, you will need to be able to SAFELY lift the entire vehicle enough to keep the transmission pan level and give yourself enough room to work underneath. If you can do this, then here's how:
This WIS doc that describes the procedure:
http://benzbits.com/722_9/FillFluid.pdf
It calls for using SDS to get the fluid temperature, but you can also use an IR thermometer aimed at the transmission pan - I have verified that this is as accurate as the sensor reading from SDS.
If it is low, you'll need to add fluid through the drain plug. This is done by screwing a threaded tube into the drain plug hole and pumping fluid in. You can find the tube online for ~$25, for example:
Save on Assenmacher Specialty Tools ATF129 at USA Tool Warehouse Automotive Tools
You can use a simple hand pump, such as a cheap one you can buy at Harbor Freight like this:
Gear Oil and Fluid Pump
You'll also need some ATF that meets MB spec 236.14. Shell ATF-134 meets that and is usually much less expensive than genuine MBZ oil (like $7/qt vs. $25).
Having said all that, a few more thoughts: First, you have an early model 722.9 transmission and these are know to be more prone to failures. One problem is that the torque converter degrades and dirties the fluid. Regular fluid and filter changes every 39K miles are required. If yours has never been serviced, this could be contributing to your problems so that needs to be done.
Also, the speed sensors on the conductor plate are known to fail. The conductor plate in this transmission also contains the TCU, which must be SCN coded as it's part of the drive authorization security system. That can only be done by an authorized dealer with a "live" copy of SDS with access to MBZ corporate. Most dealers charge around $1,500 for the job, and that includes a fluid and filter change, which usually runs over $400 in itself.
BTW, when doing a fluid and filter change the torque converter needs to be drained. This requires manually rotating the engine crankshaft so that the drain plug is accessible from the access port on the bell housing. Some dealers get lazy and just claim "yours doesn't have a drain plug". That may be true on the most very early version of the 722.9, I believe only those of MY2003 and very early MY2004. I am pretty sure that by MY2005, the drain plug was added. If there is no drain plug, then the fluid needs to be flushed via the cooling lines to get all the old replaced with the new.
One more thing - there was also a change int he pan and filter design:
http://benzbits.com/722_9/RedesignedPan.pdf
If anyone needs a new pan, i have one. I bought it thinking on of my cars needed it but it did not.
As you discovered, the 722.9 has no dipstick or even a dip tube. It is checked from underneath by removing the drain plug and observing the flow rate at a specific fluid temperature. Your problem could be low fluid, but it could be other problems. I'd get a proper diagnosis with a scan tool that can read MBZ-proprietary DTCs from the TCU.
If you want to check the fluid level, you can. First of all, you will need to be able to SAFELY lift the entire vehicle enough to keep the transmission pan level and give yourself enough room to work underneath. If you can do this, then here's how:
This WIS doc that describes the procedure:
http://benzbits.com/722_9/FillFluid.pdf
It calls for using SDS to get the fluid temperature, but you can also use an IR thermometer aimed at the transmission pan - I have verified that this is as accurate as the sensor reading from SDS.
If it is low, you'll need to add fluid through the drain plug. This is done by screwing a threaded tube into the drain plug hole and pumping fluid in. You can find the tube online for ~$25, for example:
Save on Assenmacher Specialty Tools ATF129 at USA Tool Warehouse Automotive Tools
You can use a simple hand pump, such as a cheap one you can buy at Harbor Freight like this:
Gear Oil and Fluid Pump
You'll also need some ATF that meets MB spec 236.14. Shell ATF-134 meets that and is usually much less expensive than genuine MBZ oil (like $7/qt vs. $25).
Having said all that, a few more thoughts: First, you have an early model 722.9 transmission and these are know to be more prone to failures. One problem is that the torque converter degrades and dirties the fluid. Regular fluid and filter changes every 39K miles are required. If yours has never been serviced, this could be contributing to your problems so that needs to be done.
Also, the speed sensors on the conductor plate are known to fail. The conductor plate in this transmission also contains the TCU, which must be SCN coded as it's part of the drive authorization security system. That can only be done by an authorized dealer with a "live" copy of SDS with access to MBZ corporate. Most dealers charge around $1,500 for the job, and that includes a fluid and filter change, which usually runs over $400 in itself.
BTW, when doing a fluid and filter change the torque converter needs to be drained. This requires manually rotating the engine crankshaft so that the drain plug is accessible from the access port on the bell housing. Some dealers get lazy and just claim "yours doesn't have a drain plug". That may be true on the most very early version of the 722.9, I believe only those of MY2003 and very early MY2004. I am pretty sure that by MY2005, the drain plug was added. If there is no drain plug, then the fluid needs to be flushed via the cooling lines to get all the old replaced with the new.
One more thing - there was also a change int he pan and filter design:
http://benzbits.com/722_9/RedesignedPan.pdf
If anyone needs a new pan, i have one. I bought it thinking on of my cars needed it but it did not.
