How stiff is a new front end? - PeachParts Mercedes-Benz Forum

JHZR2 · #1 03-16-2011, 09:08 PM

So per my DIY, I replaced all tie rods, the drag link and idler bushing. Ive noted that there is even less play in the steering (and my 82 has less than my 81, which has next to none). Very nice. But I note more effort is required too. Ive only backed the car out of the driveway so far so Im not going off of much a basis... But the stiffness/effort difference was notable.

I just want to be alert and knowing what to look/feel for in case I did something wrong... Just to be careful. So is it typical for a decent amount of effort to be necessary after doing this or should it just be less sloppy?

I torqued the idler to the right amount, 120 nm, which IIRC is 88 ft-lb. The other ball joints on the tie rod ends I tightened down by holding the allen wrench to keep the shaft in place, then just went on my ratcheting box end wrench to "wrist tight", being sure to not distort the rubber caps.

I also changed the steering shock. Maybe that helped too, but I know it didnt do much on my 83 when I replaced it there.

So suggestions? Just want to be sure I dont cause a big issue...

Thanks!

Yak · #2 03-16-2011, 10:23 PM

I believe there are torque settings for almost every bolt in the front end. After my rebuild I made a list of every bolt and went through the various sections in the FSM.

You may have taken a fair amount of slop out of the system and your alignment is now off.

If you think things are too tight with steering, lift the front end and check it without weight on the wheels. It ought to be smooth without binding.

You're also supposed to torque down various bushings only after there's weight on the wheels. This lets the car settle to it's resting position.

JHZR2 · #3 03-16-2011, 10:59 PM

Im sure my alignment is now off... That will be the job tomorrow... done at the dealer.

Steering is smooth. What bushings do you mean? I dont know that I had any bushings. Do you mean the idler arm? The rie rod ends? I did do the shocks with the front end on the ground.

JHZR2 · #4 03-16-2011, 11:01 PM

btw, youre right, 35nm g\for the tie rod end nuts and 20nm for the clamp nuts for adjustment...

Yak · #5 03-17-2011, 08:25 PM

Quote:

Originally Posted by JHZR2

Im sure my alignment is now off... That will be the job tomorrow... done at the dealer.

Steering is smooth. What bushings do you mean? I dont know that I had any bushings. Do you mean the idler arm? The rie rod ends? I did do the shocks with the front end on the ground.

Wrote bushings, meant bearings.

From the FSM section on the UCA replacement 33-500, in the notes up front that people skip while getting to the wrench turning part:

"The UCA bearing on front end, the UCA support on torsion bar, as well as the torsion bar bearing on front end (they mean the firewall) may be tightened only when vehicle is in condition ready for driving (they mean weight on wheels). During assembly jobs, no preloads should occur on UCA via the torsion bar. If required, lift front axle half slightly at LCA on opposite side of vehicle."

For the LCA, 33-515:

"Tighten eccentric bolt of LCA bearing only when vehicle is resting on its wheels ready for driving. If this bearing is tightened without load on wheels, wrong values for control arm position would result."

LCA:
Eccentric torque: 180 Nm
Lower shock torque: 20 Nm
Support rod/LCA torque: 105 Nm (w/ M12 bolt)

UCA/tower: 80 Nm
UCA ball joint: 40 Nm
UCA/torsion bar: 65 Nm

Idler arm: 120 Nm
Drag link: 35 Nm
Tie rod: 35 Nm
Steering knuckle arm: 80 Nm

And the grandaddy Pitman arm: 160-200 Nm

JHZR2 · #6 03-17-2011, 10:32 PM

if that is the case, how does one do an alignment? Do they drop the car down every time they adjust?

I think I fixed the washers when my wheel was up in the air. I guess Ill untorque and retorque them with the wheel on the ground. Since all the parts were previously done, everything was settled, and I doubt it matters... but Ill do it all the same.

Car is driving great after the alignment.

Yak · #7 03-18-2011, 06:13 PM

Quote:

Originally Posted by JHZR2

if that is the case, how does one do an alignment? Do they drop the car down every time they adjust?

I think I fixed the washers when my wheel was up in the air. I guess Ill untorque and retorque them with the wheel on the ground. Since all the parts were previously done, everything was settled, and I doubt it matters... but Ill do it all the same.

Car is driving great after the alignment.

Alignment's done with weight on wheels, otherwise your camber would be WAAAAAY off.

I think the intent is to not have the rotational shear of a tightened bearing. If you imagine the control arms hanging loose and being torqued down, then when the suspension settles the rubber is trying to return the arms to the "hanging loose" height. It could marginally affect the ride height (hence the FSM note about the LCA position) or the life span of the bearing (since it would then always be under torsion) or slightly affect ride quality (since the arms would move easier one direction than the other).

The overall effect is probably small. I was concerned when I rebuilt my front end and I thought the ride height was too high.

Checking you UCA/torsion bar bushing wouldn't affect anything with your alignment, but I'd probably leave everything else alone since you're satisfied with the way it drives.

Biodiesel300TD · #8 03-18-2011, 06:28 PM

I noticed this a bit after my front end job on my 240. I had previously adjusted the steering gear box to adjust out some of the slop before the front end rebuild. After the rebuild the steering wheel was not likely to turn back to straight after turning like it should. Your gear box may need to be adjusted back a little.

rhodes2010 · #9 03-19-2011, 12:21 AM

My 1980 300D had always been super easy to turn compared to the 300SD.
I liked it.

We did a front end rebuild that included new bearings and rotors and a rebuilt steering box. And of course steering stabalizer/shock and tie rods and
upper and lower control arms/bushings and ball joints.
The car had 300,000 miles at the time and my goal was to get rid of slop.

The slop is gone and mine too is tighter.
I will say pay attentino to the bearings, if the wheeels do not spin freely
after some driving and the rotors feel too hot then back off the bearings.

As for steering box, too tight hard to turn, too loose it gets sloppy.

But overall, I was suprised how tight it all got.

Generally speaking we are pleased.