jsut alittle problem

[sergiocharged]

ello mates
jsut for curiosity if anybody had this problem like i do

3A liear engine + unknow gearbox (plate says K50 but my car has hydraulic reservoir)when i bought it + drive shaft + 6.8"diferential

note: i dont understand the 6.8" where to where can anyone explain me from to where the measure is to do 6.8" very simple but i dont know

+ axe +tires

well the probelm that i have is when i shift to reverse u know

clutch then i shift to reverse then press the acelerator when i m steping off the clutch pedal to make the car moves (oviusly) just in reverse the car starts to rumble,jump in a few words feels horrible all the back seats or the rear part(cuase im driving =interior) starts to rumble i mean like an earthquake is horrible I M OBLIGATED to re step on the clucth pedal
to avoid the rumble .

well this problem do not produces in 1fs gear 2nd 3rd 4th or 5th
uhmmm few times but very few ones in 1st gear when im stop at the stoplight and want to move feels the same rumble but very soft but i feel it
and i say whaaaat wasnt in reverse only well i stop the car again and just acelerate alittle bit more and problem soft but the reverse not havent been solutioanted i though was the exhaust line that was very but very close to the drive shaft.i jacked upthe car and saw the driveshaft was hitting the exhasust line even the drive shaft has linear marks on it so i took the car to the welder a few fire here and there and the exhaust line is separated now so i said yeeees no more reverse probelm but
the problem still until now
so my friends told me to drain alittle bit of diferential oil to see if theres abit of metalpieces to discharge the posibility of a wearing or anything else
but for me maybe can be other problem what u think
its strange just IN REVERSE?
i verified the gearbox mounts seems good but imgonna rechek
maybe attak pinion
any sugestion that can i make in my little garage