It is fun and all.....

[SargeGTO]

.....but I disagree and solicit your thoughts.
On a major LS1 forum I mod it seems to be common practice to do smoking figure 8's after changing the differential fluid. Now the justification for this is to "introduce the friction modifier (FM) properly" ....Well I disagree and here is why ( in my simpleton thought process

)
You have been running a lube/FM mix for XXXXX miles anyway....draining the fluid isn't going to wipe clean every last bit of the previous "film" off the gears etc. So by draining and refilling all your really doing is replenishing the fluid with fresh fluid and there is no need to "introduce the new FM to gear surfaces/clutch plates etc. by doing smoking figure 8's in some empty parking lot. I doubt GM did smoking figure 8's in the factory parking lot when the car rolled off the assembly line.....what do you guys think? I feel simply driving normally will mix the "soup" properly and allow the FM to mix and do its job. So I ask this forum......
Do smoking figure 8's after replenishment of diff fluid and FM modifier?
Internet rumor?
Old Wives tale?
Waste of good rubber?
A must for proper operation?

 

[LAGA]

In a couple of different places, including this forum. I have read that after a fluid change with FM you are suppose to do SLOW figure eights in a parking lot.

 

[zrxkawboy]

Your reasoning on this makes sense to me, Sarge.

 

[Pablo]

Smoking not required.

 

[heyjayman]

I have never heard of that practise. For something that uses the centrifugal governor counterweight, such as the trucks with the G80 RPO, that can really cause problems.

I was taught - and most shop manuals also recommend this procedure - to drive SLOW figure 8's half a dozen times or so. In a LS with bias spring preload, the plates are always lightly rubbing together anyway, and this ensures the FM is evenly distributed

In the truck G80 RPO, the clutch plates are almost completely unloaded. Only when there is a speed differential - at low speeds only - will the pawl engage to force the clutch plates together

When I put the wrong gear oil in the rear axle of my 2000 GMC Sierra, my G80 stopped working. Driving the slow figure 8's didn't seem to help get the FM onto the clutch plates

I ended up taking off the rear cover, and squirting FM directly onto the clutch plates. That seemed to work.

It's really important to change the gear oil before the FM is used up. In a commercial/industrial application, such as a powershift transmission, if you let the clutches chatter/slip/grab, you end up with glazed clutches and a hefty repair bill

 

[Gary Allan]

The only reason I've ever done figure 8's is to see if there was too much chatter in a clutch type posi. No burn out required (as Pablo said).

I'd put this in the realm of plugging your filter bypass in SBC engines. Some famous guy just did it one day on a notion or theory ..went on to win some races or whatnot ..and it became gospel. No one really thinks to question it for sensibility.

"It's just what you do".

I'm open to alternative points of view here.

 

[1sttruck]

Slow, tight figure 8s seems to help to redistribute grease in higher mileage CV joints.

 

[GMBoy]

I agree with the gentlemen above. NO smoke-outs are required, just a slow figure 8. New vehicles (atleast at GM plants) are driven on a short road course before shipping that actually does include a figure 8. While primarly designed to detect chassis defects, I'm sure it helps with the axles too.