MotorHead

I has some noise in my rear end seemed it started just after the new motor was installed. I changed the diff fluid and added 2 bottles of GM posi additive and it realy made a difference but there is still some chatter/vibration/noise left. The oil change got rid of about 75% of it.

I was reading another thread and it mentioned that you can change it again to fix the problem, anyone have any experiences with this because the posi additive I have to get at GM and the price up here is a joke l

Eddie 70

Several years ago, the 79 I had at the time had the chatter in the rear end. I wound up going down and buying several bottles of rear end dope and changing it twice. I put just the dope in the rear end and drove it around in a big parking lot in circles in one direction then changed directions. Came home and changed the fluid. Did this once more. For the final fill I put in Mobil One and the additives. Never heard from that rear diff again.

MotorHead

Good enough for me I am going to rebuild the rearend this winter just want to make it till then

75 Hot One

Motorhead, from your profile you've got an impressive engine. Do you know how much HP & torque it makes? How did you get the intake manifold to fit under the hood? Any reliability issues with the roller lifters? Are you running pump gas at 11:1 compression ratio?

comp

don't see what it can hurt except a few extra $$

MotorHead

I am going to put in some Royal Purple synthetic 75W-90 and the 2 bottles of the GM additive has anyone tried this ?

THe motor is a lot of fun, it will spin the tires ( 295's ) at 50mph, probably the reason why the rear end is acting up

I use a K&N drop base air cleaner and run 93-94 octane pump gas with no problems actually had the timing advanced to 45deg by mistake when I first got it running and it ran fine. The solid roller really makes power above 3000RPM but the motor has so much torque you can drive around in 4th gear at 1500RPM all day long.

Basically the best of both both world here. I have had to adjust the lifters three times in 2500 miles but I think it is normal untill everything in worked in then I won't have to do it so often. I have not checked to see what they look like yet will do that at the end of the season.

DD has the motor at 575HP and 550Ft/lbs and 400ft/lbs at 2000RPM.
I'll see what I get on the chassis dyno in a couple of weeks and I'll take it from there

Frank75

Try the driving in circles trick. Mine made noise after a fluid change until I did this and now it's better.

75 Hot One

That sounds like an amazing engine. I'm looking for ideas for a new engine but yours sounds about the best for a 406 that I've seen. World Products/ Bill Mitchell makes a 406, 9.5 CR I believe, but it's only 450 hp.

MotorHead

Anyway I changed the oil again and it is perfect no noise at all

We will see if the noise comes back after I get on it few time

I put in the Royal Purple 75W-140 synthetic and 2 bottles of GM additive