Hello All,


Car: 1978 280CE
Transmission: 722.112


I need to replace the ring gear on the flywheel next week, and will obviously need to drop the transmission. Unfortunately, the ring has some chipped teeth. I am hoping to use the torque wrench during reassembly. Does anyone have, or know the torque specs, for this model transmission? Torque specs for the starter bolts would also be handy to have. Even a 'lead' to an on-line link would prove beneficial.


Appreciate any help you guys may provide!


Mark

mm:

The flywheel & flexplate bolts are tightened in two steps:
1) 30 lbft.
2) 90-100 degrees of rotation
If the diameter of the necked portion of the bolts is 7.3mm or greater they may be reused. If less than 7.3mm, replace.

If the starter bolts have not been previously removed, they are likely to be, um, "surprisingly" tight. The matter of using a torque wrench to re-tighten may be academic.

Hi Frank,


And 'thanks' for the reply. So if I understand steps 1 & 2, tighten bolts to 30 ft. lbs., then, tighten about 1/4 turn additional?


Obviously I won't know about the bolt neck diameter tell I get them out. That being said, I did order a new set of bolts based on the vehicle's VIN and whatever footnotes existed. TBD.


As to the starter bolts, thanks (maybe) for the word of caution. I've got the correct Allen head on a 1/2" drive socket, 24" & 36" extensions, a flex adapter, and an impact gun. I sure hope that will suffice. I sure hope ...


Mark

Frank,


I probably should have mentioned it earlier, but may also replace the pump seal. I suspect there will be bolts holding the primary pump housing in place. Torque value?


Thanks,
MM

If the front seal is not leaking, it may be well to leave it. While not difficult to R&R, it would best be done without removing the front cover of the trans, as the bolts that retain the pump in the front cover come from the inside. A double hook puller is indicated in the literature.

Should you choose to remove the front cover, the torque for the cover-to-main case bolts is: ~9-10 lbft.
The pump-to-cover bolt torque is: ~15 lbft.
A fresh gasket for the front cover will help.

Hi Frank,


Just so I understand your explanation, the Pump can be removed without removing the Bell Housing.

1) First order of business is to pull the Torque Converter. There is mention about removing a small Plastic Plug, and I see some cautionary notes about the 'Tabs' being prone to breaking. What would cause them to break during the process?

2) From what I can see, there are several Bushings and a Seal located on the Input Shaft just forward of the Pump. Those get removed. Then the Pump needs to be removed. You indicated a double hook puller is used to pull the Pump off the shaft. You also mention "it would best be done without removing the front cover of the trans, as the bolts that retain the pump in the front cover come from the inside". This is where I get confused. If the bolts that secure the Pump come from the inside and through the Bell Housing, how can they be removed without removing the front cover? I see no nuts holding the pump to the four bolts, so I am assuming the Pump is threaded for the bolts.

Sorry for the details, but the time to educate myself is now, not in the middle of the job.

Thanks Again,
mark

The bell housing and the front cover are one piece.



Since the bell and the front cover are one, the bell/front cover indeed is removed to gain access to the pump bolts.
The only seal at the front of the trans is pressed into the pump, and seals on the neck of the convertor. The puller mentioned is to extract the seal from the pump.


What manual are you reading? There is no plastic plug or tabs that I have seen. The neck of the convertor is notched for the drive lugs of the pump; the remaining part of the neck could be referred to as "tabs".

Frank,

Here is a link to the complete thread I was reading:

722.118 Automatic transmission rebuild (Monster DIY)

Citing Post #5:

Remove the torque converter from the front of the transmission – there should be a little plastic plug that needs to be pulled out of the casing and then you can just pull the torque converter off – cover it up and store it somewhere safe.

Granted, the thread is about a 722.118 and my trans is a 722.112. Perhaps that answers the mystery.

All that being said, I am taking the MB to my local shop, and am NOT tackling the job myself. ("Man's got to know his limitations.") I just want to know how 'deep' I want the repairs to be made, and to insure I already have all the parts I need. I have seen the tech, who I am scheduled with, rebuild Ferrari, Aston, Mercedes, and Porsche engines, and even a 4.0 on one of my Jeeps. I have no doubt he knows what he is doing. The owner of the shop lets me get hands-on, if I am so inclined.


My desire to install new pump seals is solely based on the PM point of view. Lots of labor is involved to get the trans out to replace the chipped Ring Gear, so I thought replacing the seals would be wise while we are in there. But if removing the bell housing is going to incur considerable additional time, and run the risk of 'booging' something else up, I may have to reconsider my initial course of action. Conversely, even though the seals may not be leaking today, there's no guarantee they won't start seeping tomorrow. Thus, the quandary?

Some of the original seals elsewhere have been replaced, due to failure: trans output shaft, differential pinion, steering gear output shaft, etc. Age, no doubt.

What would you do if the MB was yours, replace seals?

Appreciate your advice,
Mark

mm:

The plastic plug mentioned by Stretch appears to be an "anti-fallout" gadget that may or may not be present at this date.

A shop working on a customer car will very likely want to replace the front seal; it's a CYA matter, as come-backs are as welcome as black widow spiders.
They will have devised or purchased appropriate seal pullers.
Ergo, the seal will be replaced.

F,
Makes sense to me. The front seal seems easy enuf. As to the rear O-ring seal, I'll ask the mechanic how much more time it's going to take. If we see signs of ATF leaking from around the outer edge of the pump (as opposed to the shaft seal), my decision will be made for me. Will anything spring out or fall out in pieces when the bell housing is separated from the main case?
M

No surprises on removing the front cover. There is a thrust washer on the front planet carrier, and a seal ring that looks like a small piston ring on the input shaft.
When re-installing the cover, assure that the gap of the ring on the input shaft is in the groove as the cover is slid over the shaft. New gasket required.

Hi Frank,


Do you happen to know the torque values (722.112) for:


1) Torque Converter Drain Plug
2) Trans Cooler Lines Banjo Bolts
3) Filter Screws

Thanks Much,
Mark

see above

Hi Frank,


Just a quick follow up on 'the project', and a 'thanks' for your help. The job went pretty well. The new ring gear went on without a fight. We put the flywheel in the freezer for a couple of hours, to shrink it (maybe) a millimeter or so in diameter. The Factory manual recommends putting the ring gear in a over to expand. We didn't have access to an over. The FSM specifically states avoiding using a torch, so as to not soften the tempering of the teeth. My idea was to use two heavy duty heat guns. After about 10 minutes of heat, the ring gear dropping onto the flywheel without much effort. That was cause for celebration. All the techs watching over our shoulders were impressed!



The only problem occurred when we tried to install the two new MB bushings into the primary pump and onto the planetary carrier shaft. The dimension of each bushing was too small (probably by only hundredths of an inch) to accommodate the OD of the shaft. They were factory MB and the correct part number. We ended up driving the old bushings back in.



All dry. The primary pump seals did the job. (Actually, the old inner seal was leaking more than the outer, so we pulled the bell housing, as I thought we probably should.)


Appreciate all your info and help!


Regards,
Mark