Fiat Marea reverse gear is growling, thicker oil?

[Popsy]

Actually today thing are worse, I noticed that if I take the car (cold), then run at low rpm (to enjoy the massive torque of this powerful diesel at low rpm, lol), some highway still at relatively low rpm for a long time, there is noise from diff/gearbow when reversing, or even when changing down from third to second gear (that is new).

But if I take the car (cold), then push it (when motor is warm) at higher rpm, do frequent change down or up (like driving in traffic, this thing is slow as [censored] so to maintain in traffic you have to push it a bit), then the noise is gone, even when reversing.

Could it be the higher rpm cause more "oil splashing" in the gearbow, which helps reducing the noise? On some Fiat forum, they advise to raise the car so you can put more oil in the gearbox, good advice?

Anyway, I'm going to live with the noise and call it a day, replacing gearbox isn't that difficult on this model.

 

[Jetronic]

I'm also an advocate of slightly more oil in some boxes, but that's usually because the 5th or 6th gear gets less lubrication sometimes when used on the highway for a long time.

Could it be the bearings on the primary shaft (wheel side, not engine side) being starved from oil?

Did you check the oil level?

 

[Popsy]

The car is parked in a sloppy street, and I wondered if it could be related (not always pointing the same direction). Maybe the bearings are starving oil, but I guess the box is at least designed with some proper oil circulation?

The oil level is good, but the technical manual is not very precise, the gearbox calls for 1,7L, but when parked flat, you have to put ~1,9L to reach the level.
Some other Fiat with same gearbox call for 2,0L of oil, and I guess that's why Fiat forum advise to rise the driver's wheel and put as much oil as you can (that would be like 2,2L-2,4L), but that doesn't sound too good to put that much more oil, and nobody told me about the why in putting so much oil...

Anyway the car always had around 1,9/2L, if I remember correctly because that's what was in the box the first time I did an OC. Do you think I should overfill it more?

 

[Jetronic]

there's no real oil circulation in manual gearboxes. it's a splash lubrication system.

you could try it if you have some oil left (did the box take GL5 in the end?) but the damage is done I think.

 

[Popsy]

I don't know about GL5 oil, except what chrisri said about it.
I'll try to overfill it more...it may make it survive a bit longer, until the head broke or something like that!

 

[chrisri]

C510 gearboxes are specified for use of GL5 MANUAL TRANSMISSION FLUID, not gear oils or GL4+. Today, C510 gearboxes (modified to those in Marea) are speced for GL4+ for improved smoothness (Tutela Technix). Use either GL4+ or GL5 MTL 75w90.

Edit; those boxes are very strong, but they are getting old now, and yes diff bearings are usually the first one to fail.