It just started today ,when i go into reverse it acts like its slipped out of rreverse ,same with forward with a loud bang ,then I take it out of gear ,to then rengage but have to use a light touch when giving it gas.Lite pedal I have no issues.

read through all of this and make your own diagnostic plan based on what you hear on your car, and what you find after each inspection. factor in what parts may have been replaced before.

if the mounts are soft,or broken, or disconnected, and the driveshaft couplers are torn, it could
make your description feasible.

in this case,harder throttle apply means engine twist/ lift-up is happenning.

if the coupler(s) are torn or cracked and missing pieces it seems the angle, of the parts, changes and could still be getting some torque transfer under light throttle.

change in drive rotation direction and harder application could make the bang because the parts then collide.
a loose output shaft nut can make the drive coupler center member ( trans output flange) come off the spline somewhat. i have seen where reinstalling it with a new nut saved it. but you do need a funny socket, or use a drift and drive the nut around till tight.

get the front of the car up, block it up, reraise, block up etc. safely block rear wheels from turning on the floor of the garage. slide under with a flaslight. look for pieces of torn coupler on front one, thats where i found my 190E started breaking the coupler first. its at 150K and has sat alot. (i did front first because i was doing a clutch)
it has a 4sp.manual. yours prob. has a 5sp. its length will be a little shorter.
they relocated the exhaust on this eurobenz so the catalyst is below the rear of the trans then travels back to the P side.

i think a 17mm wrench fit the nuts and a 19/32" socket fit the bolts on my front coupler. spray paint a line and mark every part. your bolts may need a 14mm. the other bolts (i think) are 8mm allen socket head but they attach the coupler.
if you can, reconstruct its last position before breaking free. if it looks ok, hold the two members and try twisting opposite ways, (it can tear and not show obvious signs.)
on mine, a weight obscures the coupler. it's sorta (miniature brake drum) shaped, the driveshaft balancer weight, i mean.

drive shaft nut can be turned with a pipe wrench. clockwise looking toward it from the trans, looking at the center support's area.
you may be able to squish the shaft shorter and get it out of the back of the coupler. for a better sighting.
if not enough, you may have to drop the center support. all those heat shields have 8mm screws and watch out for falling debris.
everything on the exhaust was 1/2 or 13mm wrench, socket and swivel drive 3/8"

if the couplers are good, reassemble and continue diag. i drained and filled my trans and rear diff looking for metal or debris. turning the diff should produce noise, looseness, or a clunk. feel for roughness or hurky jerky. if the diff feels smooth, has no metal shavings or a magnet doesnt pull out a piece or two of debris, then you get to pull the trans.
first put it through its functions in chassis to prove your theory. look at the shift linkage bushings and be sure the line up at the shifter levers beneath can accept a drill bit passed through laterally.

theres also rear cv shaft troubles with water entry on some of these 85 vintage beasties, look for cv boot and cv axle threads to read to get your rig tip top again.
your mileage may vary.

farfegbenzin!

Well it does look like its the driveshaft coupler ,thanks for the great info .Any difference than a bland o 190e in this part # that you know of ?

i went on ebay to stare and compare. there was a search so i told it just the year and body type and the word shaft. there was a whole array of different sellers with pics. you can get a look at a new one and pick the kit as needed. you learn just by comparing theirs to yours. since the burden seems to get put on the buyer anyway, you can get numbers to search and verify in the merc catalog. i find the cheapo stuff is just that. but then, the cost of the real one can come as a surprise. alot of the 190E stuff can be unavailable. but then they have it at the wholesalers.

its like when everyone i asked about my trans said it cant be fixed, i waited an extra week after finding the numbers myself and spent $60. the wholesaler went out of his way and made it happen. i had to have all my research at the ready to get his consideration to ask the hard questions. there was a guy on here "stretch" that encouraged me with his threads and pics, and on another website the guys knew how to i.d. the car by vin and told me why i was meowing up the wrong dress.

Upon further inspection this is the problem , 1 bolt is missing in action another loose while the 3rd was tight but was the only one giving the frt driveshaft flange a bolt grab.It looks like NEW flex discs were installed forward and aft but this person didnt get the frt flex disc bolts tight enough.One good bolt needed .It looks like the front bolts need an 15 mm open end wrench with a 40 degree bend to get at the thing ,the book says support the 5spd then remove the support ,its accessable just need a tool made for the job,this is why the bolts werent torqed down.With this knowledge what was the bang coming from in your opinion ,the rearend or the 5spd?

WOW the first post was scary! glad you found the issue...

Back to sq one ,it really sounds internal to the rearend ,their is some play at the rear yolk ,1/6th of a turn,but Im getting a wurring sound from mid area of the car for some reason under mild load ,if heavy load applied its a bang which seems to come from the rear then lose of movement of the car ,clutch in and then out it remedies itself.When driving this car it did have a sound coming from the rearend when at speed while on turns ,a hummming noise ,when turn completed it went away ,I lived with it but that decision always comes at a price further down the road.Ill go back in it today and see if Im missing something obvious ,the bolt at the trans output flange Ill check ,forgot about that one since the lose or missing flex disc bolts were suspects to the condition .Can the rearend make these kind of issues on its own or is this an issue further up the line.

Man u have a 190 2.3-16 ASD diff right??

it sure as hell a rear diff ur hearing, its got play, and its got whining noises at light loads.
go on a wet road and drive at 80 kph, 50 miles, and slightly and gently go on and off the thrott. u will hear a whining noise come and go or atleast change pitch.

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Browsing on the PP site about the output flange bolt I came across one of Stretches posts that details a 5spd tear down ,the photos entail a flange bolt that has a factory pinning ,giving the bolt no way of moving off unless drilled out .This still may need to be looked at ,espicially if someone has removed the 5spd for service before and replaced this bolt with no pinnings.

It is the rearend you mention JR but A Closer look at the rear flex disc has me tearing out the driveshaft for rebuild ,Ill replace the u-joints ,carrier shaft bearing and 2 flex disc. I feel the problem is the driveshaft through out because with further testing the noise I have little doubt now that this is it ,their is way to much movement going on .Ill mark the 2 shafts before removing them apart for balancing reasons ,should I let a driveshaft company do this work or is it DIY friendly on replacing the u joints .Im limited on any special tools in my tool closet.This car being a road heavy cornerer has scene plenty of twisty turnies in its 29 yr plus life .

The Update results are that the new parts were not the fix needed.I didnt replace the u joints ,the new parts are a new rear flex disc ,center support bearing and trans mount.The frt flex disc looked new and once I had the new trans mount on everything up frt was solid again.Im going out on a limb and thinking it might even be forward of the trans ,maybe a bad engine mount causing such a movement to allow the driveshaft to remove itself out of its sleeve.Im checking the engine mount under new inspection ,then tearing down the driveshaft complete to look upon the rear shaft of the 5spd and the frt flex disc .After this process it will be right or its dropping the 5spd to inspect the clutch assembly or something worse.

Hydraulic issue ,it does pay to inspect or suspect everything before making a conclusion ,this was my first impression so I went with it as the only issue, not fully looking at the whole system. The driveshaft had plenty of issues along the way so those have been addressed but the next parts will be onward to fully bring up the hydraulics .A slave and master cylinder for the clutch along with a new brake booster for the brake system and it should be fixed.I was getting a slipping of the brakes shortly before which indicates a brake booster leaking .Ive owned a 5pd 190d with this repair needed but it wasnt so on and off as this one ,it also leaked brake fluid like a sive were this one is very slow to show evidence of a leak.

Sounds like any other manual trans that's either miss adjusted and popping out of gear, or it's simply worn out. SLK320's and Crossfires had the same issue. The cause being a first gear assembly incorrectly manufactured. We've changed a number of them and it's cured the issue. I'd recommend checking the linkage first, the the fluid for metal chunks
Good luck

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Thanks for your input ,I was under it this morning and looked at the linkage ,the bushings are all their but they could use replacing ,the 5spd shifter is really worn ,Ill start here ,then drain and inspect hydo fluid.Ive noticed the brake booster looks heavy duty ,bigger than a stock 190e ,is this an upgrade from the factory?Ive seen a 400e booster install on a 190e before ,it looked like bolt on upgrade with no issues, Ill be replacing this with the slave and master clutch cylinders.It will take a day of tinkering once I have all the parts in.This was a poor old car before I started wrenching on it ,it still needs a ton of service from neglected items but has come a long way in a yrs time.I have another one in the wings which is an 87 auto cossie ,these take a little more time and care than my diesels but the miles vs smiles are kind of worth a few more dollars .

BMW, VW, Porsche Clutch Bleeding - YouTube
Heres a good way to bleed your clutch .