I promise you its not a tensioner misadjusted issue. Its the fact that the tensioner side of belt is the part of the belt that gets loose and vibrates. the tensioner is supposed to put the proper slack in the belt automatically. during a high rev the slack side goes overly slack. the rod comes out quick and easy. but takes a long time to back up if it come out too far. in the case of blue belt the tensioner it over adjusts. I dont know why it does it compared to stock mistu belt. I just know there was no other explanation in my case.

 

The driven gear supports the stubby. The driven gear has huge thrust surfaces supported with high oil pressure. The gear stays perfectly centered in the housing. There is positively no way this gear has anything to do with the pump failures. There is no load on this gear accept to drive the oil itself. And it never galls or goes bad. It is definitely the drive gear that is being pulled to the side by higher than normal belt tension.

 

Ah the internet. Lots of info. Some good. Some bad.

Belts and chains that are tensioned too tight, can cause failures to anything they are attached to. On 4g63 timing belts this can be the oil pump, crank shaft, cams, and the cam journals of the head. I have seen, or heard all of these as a result of timing belts being too tight. I definitely have heard of more of these with kevlar belts.

I am sure some of these kevlar belt pump, crank etc failures were tensioned incorrectly, but I am positive one of them was tensioned correctly, and believe there are more. There is a spec to measure from the tensioner body to the arm on all 4g63 tensioners. I believe they are all .150-.180 no matter the tensioner thru out the years. Don't quote me on that part though. The grenade pin should slide in easily if you are with in the spec. Anyway, I haven't decided against the gates kevlar yet, but I am definitely setting the belt tension on the loose side of that spec when using kevlar from here out.


Stubby shaft. The gear that the tbelt wraps around is not even the gear that the balance shaft is on. We learn new things everyday, but there are just too many stubby shafts out there, installed by too many reputable, and record setting shops, that have had great reliability.

AMS sells a product. They obviously are going to have to come up with a reason why you should spend money on that part. Obviously they believe in it, but let's not forget that we ditch the bshafts because they cause problems to begin with. Spun bshaft bearings, broken bshaft belts taking out tbelts etc. I am not against the turned down shaft, an have considered doing it myself since it is all of 20 minutes worth of work. I just don't believe it has anything to do with this subject, or a necessity.

 

Well put, my thoughts exactly.

 

yes very well put jimib - I have my belt on the loose side as you said.. not loose enough not to be able to slide the pin in and out easy but loose enough as i could get it and still slide the pin and i experience no whine at all.

 

My buddy just installed a gates belt on a evo 8 and had 0 issues after install.

But his car also has the ams balance shaft eliminator kit

 

Cool story.

 

Thanks for the info. I have used an unknown amount of gates belts on evo's and subarus, and only had a problem once with my own car. The belt wasn't straight, it was making the tensioner pulley wobble making a ton of noise. Thankfully the distributor I bought it from overnighted me another belt immediatly. That was over a year ago, and never had a problem with blue Gates belts again.
Thanks for the warning tho, definatly going to examin the install with these belts even closer now.

 

I replaced my stock t-belt/balance shaft belt with the gates set 2 years ago, and when I first put them on they did have a whine to them, sort of like a supercharger. After a while of driving though the whining subsided and it sounds just as quiet as the stock belts. I think it's just due to the belts being so stiff from the kevlar.

 

I have heard all kinds of weird belt noises from the blue kevlar style belts.

I have seen many oil pump failures with the stub shaft and FEW (none that I can actually remember) with a balance shaft with the counter weights machined off.

As AWD94Coupe said, the stub shaft supports the driven gear, not the drive gear. Its not the side loading from the timing belt on the drive gear that causes the problem, its the side loading on the driven gear from the oil being pumped between the gears. This force will put all the support on the stub shaft thru the small bushing race in the oil pump rear cover. Keeping the long shaft reduces the angle that the driven gear can pivot, reducing the chances of the driven gear teeth from digging into the inside of the oil pump housing.

This is all just theory until someone with some serious engineering knowledge nuts up and puts the time and money into testing this with the proper method and equipment.

 

First of all, I have absolutlely no problems with AMS. You guys put out some great cars, and most definitely are on top of your marketing.

As far as the stubby shaft/turned down shaft debates go... The instances we are talking about in this thread with the oil pump failures are failures where the drive gear has egg shaped the bore the shaft rides in. Totally different deal, and imo not possible that the driven gear could cause problems with the drive. The other way around sure.

If it wasn't for the fact that balance shaft bearings spin, and balance shaft belts break and take timing belts out with them, I definitely wouldn see anything wrong with running the shaft with the weights turned down. I just do not think its necessary, and keeps the potential problems. Isn't the oil pressure going to be equal all around both gears? If you have 100psi of force on one side of the gear from oil pressure, isn't there going to be 100psi on the opposite side stabilizing it? Also there have been confirmed cases of pump failure with a turned down shaft.

As far as someone needing to nut up... I would hope that you guys already had if you were selling this product.

 

One thing... I guess the bshaft belt wouldnt be an issue here..

 

FYI - I only use the stock OEM timing belts on my race Evo - period - never had a problem of failure

 

I rarely see the bearing on the rear balance shaft spin, it is supplied oil thru the shaft directly from the pump. If they do, its usually from oil starvation from a low oil condition. I do often however see front balance shaft bearings spin, the shaft that is driven by the balance shaft belt. This shafts bearings are fed oil from the main oil galley, where the pressure has already been distributed to other oiling areas and most likely much lower.

 

I have the gates blue belt that has 20 minutes use on it. Will sell for 75 shipped.