HP60 Issues

[wildman4x4nut]

Blaine I am hoping you might shead some light into this whole issue.
http://www.jeepsunlimited.com/forums...d.php?t=824879

Now one idea I have had is to send the new R&P off to Longfield for some Cryo treatment. From your experiance will it/can it help?

[mrblaine]

Originally posted by wildman4x4nut
Blaine I am hoping you might shead some light into this whole issue.
http://www.jeepsunlimited.com/forums...d.php?t=824879

Now one idea I have had is to send the new R&P off to Longfield for some Cryo treatment. From your experiance will it/can it help?

I'm not convinced that your set-up was good enough. High Pinion rear ends need to be set up differently because the pinion is trying to walk out of the ring gear under load.

That's why the tips of the gear teeth are pushed over and the stress fractures start high and work down towards the root of the tooth.

I'll call John and ask him to take a peek tomorrow if he doesn't see this before I get to him.

He'll have a better insight into how to set them up as well as which gears will better take the abuse.

Personally I still think there is a pinion bearing issue with your housing or will think that until I know differently.

[wildman4x4nut]

Blaine,
Thanks for the insight. I am less than happy with Tera (like that is any surprise). I can use/will take any advise you have to offer. And if my R&P guy here doesn't feel comfortable about setting up the next set I'll take it to someone who does.

[mrblaine]

Originally posted by wildman4x4nut
Blaine,
Thanks for the insight. I am less than happy with Tera (like that is any surprise). I can use/will take any advise you have to offer. And if my R&P guy here doesn't feel comfortable about setting up the next set I'll take it to someone who does.

Let's see what John has to say first. I'll trust his advice over any I can get from anyone.

[SavageSun4x4]

I showed the pics to a friend of mine and his thoughts were in line with Blaine's. I might add that he also HAD a Tera 60 CRD...

My exp would also bear this out...from my racing days.

As for Cryo treatment it can be beneficial for lots of components. But I would see no need and very little gain for the $ in your situation. Nor do I feel that added strength in the R&P is the solution here.

My exp with breakage in the diff has always pointed to one or both of two things. Improper clearances leading to some degree of movement and or extreme torque loading.

There is a small degree of slack in the drive-line from crankshaft to the R&P. Albeit not much, when you add it up it can become significant to hi-hp/torque input at 7,000+ RPM standing start.

In my drag racing days I would always stage at the lights by smoking up tires to heat them, get a good straight line on the track etc.

Many racers would stage past the line and let the spotter push your car backward into position. What this does is reverse the spaces in the drive-line. Now come off that clutch at 7k and the drive-line has to take up a few .001's in a highly explosive manner. That slight movement can be enough to literally rip teeth off gears and on occasions actually explode a diff...ask me how I know

So I and many others would put on the brakes or line-lock and gently ease out the clutch just enough to engage slightly to take up any drive-line slack...thus reducing breakage.

[mrblaine]

I spoke with John and he feels the set-up was not correct and the gear brand might not have been the best choice.

The pattern needs to be as deep as it can get on the coast side and so much so that you may even get some gear noise when it's at highway speed.

He suggested you try a set of Precision Gear brand gears.

[wildman4x4nut]

Blaine thanks for taking the time to ask. I'll pass this info onto my gear installer and will go from there. The first set of gears to break were Precision and by chance I have a gift certificate for a set of Precision Gears.

Rick

[wildman4x4nut]

Okay some people wanted to see the gear patterns.
Old gear set, Precision Gears




New gear set, Yukon Gears

[JLemieux]

Let me preface this post with some terminology. The drive side of the ring gear is side that has less of an angle to it as shown in your first picture. Coast side has more of an angle to it as shown in the second picture. A high pinion differential mounted in the rear of a vehicle drives foreward on the coast side of the ring gear and backwards on the drive side. The toe of the gear tooth is on the inside diameter of the ring gear and the heel is on the outside diameter.

In looking at the coast side of the Precision gear set (2nd picture) it is evident by the high coast pattern this gear was going to fail. Only half the gear surface was ever contacting the pinion gear so all of the load was in a very small section of the ring gear. To bring the contact pattern down towards the toe of the ring gear tooth, try setting up the gears with the minimum amount of backlash (.004 is the lowest I would go). If the contact pattern is high on the r.g. tooth (heel contact) it will only go higher when the gear is under load. Now running minimum backlash is going to bring the drive side pattern down towards the toe aslo possibly causing noise on coast / deacceleration. If your gear guy can't get that coast side down towards the toe he will have to try a different brand of gear set.

Now as far as gear sets go, these days there is no guaranty that a Precision gear is in a Precision gear box. Gear suppliers, in order to keep their inventories complete will buy gears from other manufacturers and put them in their own boxes until their own shippments come in. Most of the suppliers that do this usually swap gears only with manufacturers they feel have a similar quality gear. Look at the ID markings on the gear set. If they are the same from one manufacturer to the other, it is made by the same gear maker and likely will have the same pattern.
Some gear suppliers will have a "Made for mail order" gear set and a "Made for the gear professional" gear set. When it comes to gear set you usually get what you pay for. The second gear set you tried was from Randy's Ring and Pinion (Yukon Gear). I have had some great gear sets from them (easy set up and great gear pattern). I have had some noisey ones too. Buy and install only premium gear sets.

I have a set of Midwest 4.56's in my Rock Jock D60. They set up fine with a good pattern. They make noise. I live with it. So far they have survived 30k mikes behind a 5.7 Hemi and in front of a trailer.

Is there is a problem with the Tera 60 housing? I don't know, I don't have a lot of experience with using them. If a housing is not machined exactly correct, no gear set is going set up right.