2QUIK6

Per my other posts on my front engine noise, does anyone have any close pics of the LT4 Extreme Duty timing set waterpump gear?

I heard they look a little different than the stocker so I want to verify whats on my car as I did not do the install originally.
Here's apic of whats on there.

TobyZ28

I have one kicking around, will need to dig it up for you

Jim D

If I remember correctly, the extreme duty set had a tiny hole drilled in every 4 or 5 teeth on the cam gear that drives the water pump gear. That was supposed to prevent too much oil pressure between the teeth from building up or something to that affect...

2QUIK6

Well..I found this pic on Thunder Racings site...not good

and a completed ebay listing showing a similar wp gear

Can someone confirm that the LT4 ED gear has 3 holes in it instead of the 6 like the one in my pic?

TobyZ28

Hey, i dont have a camera to use at the moment (i can get a pic maybe later today though) but i do have the gear here. it looks different then yours. The WP gear in your picture looks like it has 6 holes in it where mine has only 3 holes.

wrd1972

It appears you have the wrong water pump drive gear, the ED gears has beveled edges and lees overall tooth. Maybe thats the problem.
The ED gear is on the left.

As you can see you cearly have the stock LT1 water pump drive gear.

TobyZ28

although its really hard to tell it looks like the teeth are a tad longer on the stock pump gear i think.. probably the source of your grinding...

wrd1972

Upon real close inspection it appears the the two gears have slightly different involute profiles. If this is the case it might cause mesh issues. The tooth lengths appear to be the same.

2QUIK6

Thanks a million for the replies, I'm trying to get the gear out now.

wrd1972

Some more really useful info:
http://forums.corvetteforum.com/show....php?t=1163505

SS RRR

You do not have to change out the gears. I've been running the ED setup for a few years on the stock pump drive gear with no problems.

2QUIK6

But do you have a grinding noise coming from the front? And the weird wear marks on the cam gear teeth, and there have been instances where the water pump gears were eventually chewed off since the metal is a softer grade on the stock pump gear.
Its appart now so its coming out.

Not to mention, if it can cause a problem..it will for me, that's my luck and it never changes it seems.

wrd1972

Why would you not install the included water pump drive gear that came with the LT4 ED timing set?

I cant believe for a second that GM throws it in the kit just for looks. There is absolutely no question the two are different from the pic I posted. Obviously it is engineered and matched to work with the LT4 ED cam sprocket/gear.

The statement "you do not have to change out the gears" will require real irrefutable proof to be valid when looking at the big picture here.

I am saying this in the interest of healthy discussion and not trying to bash you. I say you got lucky if you truly don't have any issues like being stated in this post. I believe the differences in the two gears are subtle to the point that some will get lucky if they omit it altogether but again I will trust the engineers at GM to provide the right parts.

I am very anxious to hear the solution to this problem because I will be installing the complete LT4 ED timing set soon.

Projectz28

The LT4 ED set never used to include the waterpump gear. That addition to the set is a recent thing in the last few years. When I bought mine it didnt even come with a waterpump gear. I ran the stock waterpump gear for about 10k miles.... never had a problem. The wp gear is not going to make a grinding noise, and no you dont have to replace the waterpump gear when you buy the LT4 ED set...

Javier97Z28

I ran my LT4 ED w/ stock waterpump gear for 20k miles. No grinding, no noises, no issues. When I pulled it out in favor of a double roller and ewp, the gearset had no abnormal wear.. the WP gear looked brand new, as did the drive portion of the cam sprocket.

Why did I not swap it out? Honestly I forgot to swap it when I did the install, and found it not to be a problem.