[yellow1098]

So I just made the switch 410 gear from 342 because I do a decent bit of track time. But…..the car is 75% street driven with a good bit on the highway about 70-75 mph. I also made the switch because I am able to run more gear because I have a 4L80e overdrive trans.

My questions is the detailed breakin procedure they recommend for the new gears seem like a lot

15-20 miles keeping it under 45 mph 2-3 times (no problem here)
Avoid heavy acceleration
Keep it under 60 mph for the first 100 times (shouldn’t be a problem)
15-20 mins at 65 mph max repeat process 2-3 times (getting annoying)

!drive 500 miles easy normal driving before hard acceleration or racing!
I drive the care barely 2000 miles a year! 500 might be a problem haha

What have you guys done with rear gear break-ins? Did you follow this? Do you have a different procedure? Thanks for your thoughts!

[form74]

Just went through this over the summer.
Was told by the guy who did the work to drive 30 minutes at a time and then let it cool off three or four times.

Just regular driving.

[Formulajones]

Yup what form said. I drive 20-30 minutes with cool down in between and do that 3-4 times. Then let it rip

[yellow1098]

Thank you guys! That’s way closer to what I was thinking! It’s track season here in florida can’t wait that long

Also how long does the cool down time mean? Was my other question

[VCho455]

From Yukon's site.

https://www.yukongear.com/blogs/the-...9VhhCbOFO4uyhI

From Randy's gear.

https://www.randysworldwide.com/blog...FkcWWRmdlCv73O

[Formulas]

After you drive it mild then hammer it, the next down season or stretch of spare time, doesn't hurt to take the cover off put a torque wrench on ring gear and cap bolts not backing anything off just hit them with final torque and replace the fluid,.... not mandatory to do any of this but it sure doesn't hurt

[Formulajones]

Originally Posted by yellow1098

Thank you guys! That’s way closer to what I was thinking! It’s track season here in florida can’t wait that long

Also how long does the cool down time mean? Was my other question

I do it this way

Go out to lunch, that 20 minute drive is perfect, eat lunch is my cool down time, then I might run an errand somewhere and while I'm inside is cool down time. Etc etc....

After 3-4 stops it's good to go

[PunchT37]

We used to run em on a lift or jack stands for 30 minutes or so, idling in high gear, before the 1`st drive.

[HWYSTR455]

That's what Moser says, jackstand, idle in drive 5 or so min, then idle in reverse 5 or so min. Then drive it 'normal' for about 50 miles. Then let it rip.

.

[DaleO]

This isn't a smart-alec question. Did the auto manufactures, or differential manufactures, adhere to a break in process?

[72projectbird]

I've always just beat the bag outta them as soon as they're installed. So far so good.

[Keith Seymore]

Originally Posted by DaleO

This isn't a smart-alec question. Did the auto manufactures, or differential manufactures, adhere to a break in process?

Naw.

They go wide-open throttle on the roll test and then wide-open throttle shuttling it in the parking lot.

The saving grace there is probably that they're short bursts of activity followed by long periods of sitting.

K

[67Fbird]

The difference between the Auto MANUFACTERERs and US???? When assembled they have the ability to measure frequency/harmonics. We can measure 2 things, depth and back lash that SHOULD put them in the HARMONIC relationship that they were lapped to. Well .0005 here and .001 there changes that,that's what the break in kinda for to allow the gear to set itself in a "new" run pattern before you drive it 3 hrs and overheat it. It's all about heat in a hypoid gear.

[Keith Seymore]

Agree - it's all about the heat.

K

[mgarblik]

Hypoid gears do really run hot too! Especially while breaking-in. I would expect a 4.10:1 gear set to make a little whining noise, even with a proper break-in and set up. Not many pinion teeth! Probably a 41-10 tooth count. Just be aware. In my experience, 3.73 and lower numerical can be set up silent. 3.90 and higher may make just a little noise.

[78w72]

I have Yukon 3.23 gears in a beefed up 8.5 behind a 500+hp engine that does lots of low 11 second drag use. I followed exactly what Yukon says for break in procedure, why risk it by cutting corners or making up your own procedure? Wasnt all that big of a deal since the 100 miles in 5 intervals goes by pretty fast, then just take it easy meaning no towing or drag strip/racing use the first 500 miles... then change the fluid & add GM posi additive if its a posi.

After 10 years of street & strip abuse the rear end as a whole is doing great with no noise... knock on wood was worried almost 600lb/ft of torque & good traction would kill the 8.5 real quick.

[yellow1098]

So my update is ….I did the first low speed 2-3 15 mile break ins and also just finished the under 65 mph highway runs for the first 100 miles…..

So next is just the 500 miles before racing and hammering it

Right now it is silent under 50mph but during acceleration between 50-60 it wines pretty good but when I left off the throttle its silent….it also seems to go away about 60mph

My question is …..does the noise go away a bit once it breaks in and the teeth wear in some??? Or is this just the nature of going 410’s like some have mentioned