Hey guys....I've been trying to work a couple kinks out of my recently installed LE2 (daily driver) setup. I'm wondering what kind of low RPM's other LE2 setups are able to tolerate on the road (in overdrive for example) without the car acting like a manual shift that has been shifted into a taller gear too early. You can take a look at my sig, but basically built it from the ground up using all of Lloyd's recommendations. Only thing I still have that is not ideal is the stock 3.23 gears, but do have a Vig 3200 stall and PCMforLess tuning for that gear. I have already gotten Bryan to bump up the torque converter lockup points and couple times and am getting ready to try his latest tune that bumped it up even more, but in the meantime, thought I would at least ask to see what kind of low RPM's other LE2 owners are running well at.

In a nutshell, with my setup, when my car drops into overdrive, I'm running right at 50mph at around 1,700-1,800 RPM and there is a steady, fast vibration and it's like the car is just struggling at such a low RPM. Once I get past 2,100ish, things smooth out. I have, of course, done all kinds of other troubleshooting such as balancing my drive shaft, new flywheel, etc. but it just seems like my setup hates those low RPM's. I don't mind continuing to tweak the tune and even making it where I don't lock up below 2,200 or so, but didn't want to go that route if I find that others with LE2 and 3.23's are doing fine locking up below 2K in overdrive.

Sorry for the wordy email....thanks in advance!

Robert

 

Is this 'vibration' cam surge?

 

No, almost positive it's not cam surge.....it's more of a very steady vibration...like the car's shuttering b/c of not enough torque to push the car along at such a low rpm. Like I said, the best analogy I can think of is if you shift a manual car too soon.

 

I would move your shift points up some. If you were to hold 3rd till 60-65 or so things might be much smoother. I believe one of the top reasons the 4l60's dont last is b/c people abuse overdrive too much. When I was running my LE2 stuff I found it much easier if I made it so overdrive kicked in when I got to my crusing speed and let off the gas, and out when I went to speedup. BTW is it a stock or rebuilt bottom end?

Edit: just read your sig maybe your engine is out of balance and your getting a vibration from that

 

Well, it sounds like your kickdown tables need work. It also sounds like there needs to be some street tuning done to find the right timing for low rpms. My cam is similar in size to an LE2 cam and beside resonance, I don't have any issues with under 2,000 rpm operation. If you want me to look at your timing tables (kickdown tables would be too much of a pain to do over the internet), send me the tune at Sweetred95ta@hotmail.com .

 

Nothing is stock....except the block. Went with with quality/forged parts from top to bottom.

I see your point about the shift points...and maybe that's what I should be bumping up instead of TC lockup points? As a matter of fact, when I first started getting tune updates from Bryan, he asked if it was shift points I was looking for and I told him no, that I thought it was the TC lockup points I was interested in...TC seemed to be locking up too early. But maybe the shift points are something I should revisit. As I said, all the other gears feel fine....doesn't seem to be "locking up" like that at a low rpm in any other gear except overdrive. I just wasn't sure if an LE2 setup should generally be able to lock into overdrive at 1,700ish with 3.23 gears without these kind of issues.

 

get different gears, i would get 3.73s, that should help out a little by raising your RPMs a couple hundred

 

I think what you are feeling is cam surge IMHO. There are many people who have the CC306 cam that have complained about this, of course your cam is very similar. Maybe my definition of cam surge is wrong, someone straighten me out if so.

I have the LE2 heads with the LE1.5 (high lift) cam and I have a tad of cam surge when in 1st - 3rd gears at 1500 RPM. It is a mild bucking that goes away when you add a tad more gas or reach 1800 RPM. All this is on Ion's mail order tune, not a dyno tune which I will be getting soon. When I cruise down my neighborhood street in 4th at 1500 RPM (~25 MPH) I get the bucking which was never there with the stock LT1 cam. What I do now is use 3rd gear at 1800RPM and all is good. This is the only time I ever notice it. It appears that my powerband has shifted up by about 300 - 400 RPM or so from stock.

I have been told that this issue will "dyno" tune out when the day comes, but it is definitely NOT something I hate or something that is hard to live with. Of course i do have a 6 speed so that might make the difference too.

The problem you are having plus the power band shift was the determining factor in me choosing the LE1.5 camshaft over the LE2 camshaft, I have no regrets in that choice. You might be able to remedy this or make it easier to live with by getting a dyno tune and making sure you ignition is working perfectly, no misfires etc. Also as suggested above some 3.73's. My 4.10's over the stock 3.42's with the LE setup is just super wicked fast as well as more friendly at lower RPM's. I have NO problems period cruising in 5th or 6th at 1500, its smooth as silk.

 

My car hates having any kind of load put on it in the taller gears under 2k and my cam is smaller than an LE2 cam. I'm guessing its just from all the overlap the cam has. And it still has cam surge under 2K too, you can tune it out to a point but it will always be there.

 

Dyno tunes consist of WOT pulls on the dyno. Unless you tell him to make changes in the lower rpms (part throttle), the car will drive similar to how it drove before the dyno session. I would suggest street tuning with a wideband.

 

Mine does the same thing if i let the rpms drop that low. get gears (3.73 or 4.10) and it should put you into the usable rpm range at cruzing speeds. 1700-1800 rpms is for baby cams.

Steve

 

One possibility is the TTC (Torque Converter Clutch) may be chattering or stick-slipping. 4L60E will lock the TCC in 3rd or 4th (OD) only. I believe that TTC could be inactivated in 3rd, but not added to 1st or 2nd.

You could try this: get it to lock up and start chattering. Hold accelerator pedal steady and unlock TCC by just lightly pushing the brake with your left foot. If the chatter goes away, slow th c ar a bit with the brake, keeping the accelerator the same until the engine is down to the rpm where it chattered. If there is no chatter, add a little "gas" and try to get the chatter. Use the brake to keep the car speed the same and load the engine.

If you cant't get the chatter, it may not be an engine related problem. Also, check for something on the exhaust vibrating.

 

Some good advise here for you so far. All I would like to add as mentioned already, is to get some 3.73 gears. It makes the whole package fit together a little better. My 3.73 install made the 2800 Vig almost feel stock.

 

LE2 setup here and even with a stock stall, and 3.23's it runs great on the street. I know the stock stall is no where near ideal but I'm dreaming of a T56...

 

"It is a mild bucking that goes away you a tad more gas" <--This has been my experience with cam surge.

"My car hates having any kind of load put on it in the taller gears under 2k" <-- This was a different problem.

FWIW I had a bucking and shuddering problem on my new 383. I had cam surge before with my 350 heads and cam engine but with my new 383 I had another problem. The difference was this would really get bad under load below 2-3K. Crack the throttle blades while cruising for what should be smooth torque and it was a horrible shudder. Above 3K it revved like a sport bike. Long story short I gapped my plugs at .035 instead of the factory .050 and it was night and day, dramatic. Same ignition system as the 350, it just didn't like jumping a .050 gap in the higher compression. 383, -5cc SRP's, 52 cc chambers, 847, M6.