GRAYPNY

I talked to a reputable shop today about installing the 4:10 gears. Good news is that they can do it for $585 out the door. The bad news is that they are approximately 100 miles away and I'll have to wait while they do it. They said that they would put 2 guys on it and it would probably take from 2 to 3 hours.

They said that these gears have such tight tolerances that I should break them in. They want me to drive about 30 miles and then let the car sit for an hour. Drive another 45 miles and let it sit again for 45 minutes to an hour and then I should be home and can let it rest again. :bang: It looks like getting these gears installed is going to be an all day deal. After the initial breakin period I should drive it around town for another couple hundred miles before I put any real distance on them

On a side note, am I going to have crazy wheel hop after having these installed or am I going to have to add these?

emperorjordan

hmmmm.... this is intresting... I have never heard of this before... and I will be installing next week with a mechanic friend....

Trampus

I've never heard of that before. I didn't do any type of break in after getting my gears and I don't have any issues with noise. As for wheel hop, it seems like some people have it and some don't. I get it when I launch just hard enough to spin the tires but I don't get it when I launch it really hard.

wild stray

I was told to drive the car normally for about 500 miles before putting my foot in it! As far as wheel hop, I agree with Trampus. I havn't experienced it, but I know a lot of people on here seem to have the problem all the time.

Paul

don_w

I have to echo Leon and Paul. I was told to drive normally for about 300 miles (no drag racing or burnouts). And I haven't had any wheel hop probelms either. But, sometimes I have minor neck pain from the head-snapping.

GRAYPNY

I just watched your video Don, AWESOME! :worship:

don_w

Thanks... glad you liked it... we had a blast doing it!!

emperorjordan

haha, I second that. I love it!

stkdidy

the BMR race lower control arms completely eliminate wheel hop of every kind...tho there is a tad bit of "whirring" noise from hardened steel bushings (aka direct link)


i was not given any guidelines on my 4.10s when they were originally put in. when the rear end was rebuilt, i was told to take it easy for a couple hundred miles tho

CDGun

That does sound awsome makes me think more and more about Cutouts for my Exhaust

Cleveland

Actually, that break-in procedure is the same as what my shop (Rear End Specialties) recommended. From what I have seen around the net, its common practice really.

I put a bit over 200 miles on my break-in before launching on the drag strip later that same day.

Im yet to change my fluid because its been nice and wet around here lately and I'd rather not lay in water streaming down the street.

-Dan

Clem

My car went straight from the lift to the dyno after my first set of 4.10's (Precisons) were installed. My installer says no break-in is necessary and he does this all the time. Those gears howled.

We replaced them with FRPP 4.10's and skipped the dyno this time. We did, however, drive it like a stolen rental shortly after the install. These gears, same backlash and set-up pattern, are nearly silent.

Did making 5 pulls on the dyno with fresh gears cause my first set of gears to whine? , but I wouldn't do it again.

stang9325

Question: I get my car in 2 weeks and have the money for gears now. Do I buy the gears now and have them installed (mind you that my car will be going from the dealership straight to the garage for the rest of winter) before I pick up the car or do I save a little more, get the CAI/tuner and wait on the gears?

EDIT: Sorry to hijack, but to answer your question. I don't know the mechanical answer to it but I would think it couldn't hurt to take a little extra caution immediately after the install. I think stopping that often is a little extreme though.

MTAS

My gear installer told me that FRPP gears don't need a heat cycling break in since they're heat treated at the factory. He said gears that are not heat treated during manufacturing will require a break in procedure I drove mine like I stole it within 5min of picking the car up and have 0 problems

GRAYPNY

Well I think that I am going to drive it 50 miles and stop for lunch and then go the distance to my home. I'll "try" not to do any serious hard acceleration runs for the first 300 miles.

After that :drive:

eighty6gt

During operation, gears do not get anywhere near the temperatures necessary to do any "heat treatment."

When gears "break in" they simply burnish the contact surfaces. The high spots (what you see as scratches or maching marks) are uh, gently flattened if you keep out of the gas as much. If you get on it right away, they may be torn away, causing excessive wear. It's the same thing with many machined parts... It is not economical to finish gear teeth to a super fine RA, so some of this is done during use.

I don't know if there are any engineers around, but I can't think of a good reason to heat cycle a gearset a few times when new. I suppose some work hardening may take place...

Upon some further research, I can theorize that allowing the gears to cool, and not cycling them for long times is a bit of a good idea. Friction and heat will be much higher, as there is less flat surface for the hydrodynamic bearing to form between teeth b/c of the sharp crests on the machined grooves on the gear teeth. Too much heat too soon could lead to brittleness/tearing (as formentioned.) All of this happens on a microscopic level.

If anyone can confirm or deny feel free to jump in.

S197 GT

Hey Rich, are you getting your's done at Altered Speed?

GRAYPNY

I am having West Coast Differentials do the job. I got the name off the FRPP website and they are in Rancho Cardova just east of Sacramento. They have the FRPP 4:10 gears in stock and said that they have done two 05 Mustang GT's. Sent my tuner to Brent today for recalibration for the gears etc.

Mongoose

Prices go up every day and your dollar may not be worth as much in the spring so I would do it now!

If you were sorry to hijack you would not have done it in the first place.

Mongoose

All rear end gears are heat treated unless they come from China. Who knows what they do!!