DR'76

Just wondered why the stock programming for a '95LT1 (and possibly others???) does not contain any Torque Converter Lock-Up points after 50% Throttle in the "Normal", "Manual" or "Cruise" modes, but allows lockup at 39 MPH in 4th gear only in the "HOT" mode?

1) What is considered "hot"?

2) How is lockup in an A4 different than a released cluch in a manual?

Thanks! :smash:

Dr.

Mo_Bandy

Dr.

I'm assuming that your programming should be the same as my 96. In LT 1 edit I'm able to program the TCC engage and disengage in all gears and at all throttle percentages.

If you are speaking of the settings above 50% being set to 255 or "whatever" I can only think that the thought behind this is that when you are under WOT which you would be in most cases you are more concerned about the torque multiplication rather than full lock of the TCC , as well as at those throttle instances you are probably gong to be above the flash and stall of the converter anyways... On mine in the performance mode 3rd gear is set 255 all the way down the line. I never have quite gathered the meaning of "hot" either"... LOL

Lock at the TCC engaged as a higher value... and the release as puching the clutch in if you will i.e TCC engages at 39 mph and it could release at say 28 mph...

Hope this helps,

mo


[Modified by Mo_Bandy, 2:55 AM 5/8/2003]

HighHopes85

GM automatic overdrives generally have 4 forward gears, with 3rd being 1:1 and 4th being overdrive (usually .7:1 or .6x:1). When the torque convertor is locked up, this is as close as you are going to get to direct drive (generally it will be, some slight slippage could occur and start to damage things under massive hp vehicles). So you can be in 3rd, non-locked, 4th, non-locked, 3rd locked, or 4th locked. On the 4L60E that you are probably using, you might be able to lock in 2nd.

When you push in the clutch on a manual, the fork presses against the throwout bearing and that presses against the fingers of the pressure plate and the clutch is physically moved off the flywheel. No engine to transmission continuity is realized. In an automatic, there is always engine to transmission continuity, but the torque converter is what determines how they will be "coupled" together. When the clutch in an automatic is commanded to be locked, as mentioned before, the clutch in the TC locks and the input shaft for the tranny will be spinning the same speed as the crank. Hope it helps, -Matt

DR'76

Thanks for all the insight guys! I guess I really just need to find some open highway and see where cruising at 50% TPS puts me MPH-wise. As stated, at this %, locking the TCC might not be feasible, since it may only indicate WOT (or anticipation of) where I wouldn't want the lockup. My original thought was that at any speed (or % TPS) locking the TCC would help the MPG's and that would be something GM would incorporate into the programming...now it doesn't make as much sense! :crazy:

Thanks again!

Dr.

Mo_Bandy

DR 76,

I think what you were thinking is not out of line... we all want to squeeze as much economy and performance as we can...

I just pulled out a few of my car tests and was looking at my cruise % throttle. At like 66 mph I'm only using 10.5% and at 70 mph only 10.9% throttle. So if you were to look at the TCC enable disable settings on your programming you will find that depending on the performance settings or programmings upwards to 40 percent throttle is programmed into the TCC before they unlock it, at either 187 or 255 depending on the mph setting, which effectively for most of us would mean the VERY same thing.

I would say cruising at 50% could put you in jail :lol:

On the stock throttle settings at 50% at about 3400 RPM's the car is going to consider you running wide open throttle , just as a point of reference. Hyper tech and a few others willl actually lower these settings to allow you to enrich the mixture sooner under fire breathing runs.. anyway thats another story...

Also at least in the stock programming, again depending on whether you have a 2.59 or a 3.07 rear end ( which is what I'm running) 50% throttle the car in normal overdrive is set to shift from 3 to 4th gear at 96 mph... so I would venture to say you would need an extremely long stretch of police free highway to find your cruse speed at 50% throttle.

Hope this helps...

Mo


[Modified by Mo_Bandy, 10:46 AM 5/9/2003]

Da Wiz

I continue to be impressed by the precision given on these forums.

If I could horn in on this thread, I would like to ask a question regarding transmission downshift during WOT. I have a 94 with the electronic automatic, running a 2.59 gear.

WOT at 45-55-65-70 mph will not drop me to second gear. I can manually downshift.

How can this be? OD comes in at @48mph, and I will drop down to 3rd, but NEVER second. Since I no longer have a TV cable on this tranny, I have no idea what to adjust.

Is this normal programming, or is it troubleshooting time? :confused:


[Modified by Da Wiz, 3:15 AM 5/11/2003]

Mo_Bandy

Da Wiz,

I have a copy of a 96 LT with a 259 rear end program for LT1. I was looking at it as a reference..

Are you using any logging software? If you are If you can send me a .cvs or a text type file I can read I could probably help you out...

In the programming it shows that you would need to be almost at 80 % throttle to downshift from 3 to 2nd with anything significant as the patterns are very flat untill you get that high in the TPS settings... mainly because it is such a tall gear

There are two possibilities....

1 could be the line pressure settings at the particular speed... ( I would venture to say this is the guy!

2 could be the shift vs TPS settings.... Which can allow or not allow you to downshift into the next lower gear...

I was looking at an Excell chart i made to see what rpms you would be hitting and it doesn't seem that you would be over rev'ing

The programming shows the Normal shift at 5344 from 2-3 and 5248 from 3-4 which of course would be wide open throttle...

and the WOT downshift at up too 87 mph


As an example:

If you are running at 50 mph you are at about 1200 RPM's in 4th
3rd gear would put you at almost 1800 at 50 mph
2nd gear will put you at almost 2900 at that same 50 mph

I'm sure you probably have already worked this out...

So I would say really in answer to your question it is probably just a matter of programming.... Which I beleive in your case is a matter of flashing an eprom? I know 95 and of course 96's are flash memory and no chips...

If you like you can email me and I can try to help you sort through this if you like... I can send you a text file of some of the settings of the 96 programming , i'm sure they are probably very close if not exact... and like said if you have a logging program make a coulple logged rns and I'll see what I cna do to help you out , or shed light on what may be needed to change your settings...

Best regards,

Mo

Da Wiz

Mo, that is very gracious of you. I am currently trying to get my laptop set up for logging some of this data. I am really at the very beginning of this process, such as trying to determine if I actually have a problem.

I recently had the transmission fluid and filter changed by GM, no reported problems or bad indications. Car has 80k on the odometer.

Thanks a ton for the assistance. I better get hot on that laptop....

Mo_Bandy

Da Wiz,

I would agree it is nothing serious... generally "passing gear" will generally drop to third gear... So if naything I wouldn't fret...

When I was running the supercharger, I found that I was running without second gear for about 3 weeks LOL... The piston had somehow wedged itself in the "pack" amazing what torque can do if you have plenty of it. I noticed my test times had slipped a bit...

You can virtually program the trans to do anything...

Keep me posted...

Mo

Da Wiz

I have one of the Hypertech programmers, but their adjustments are canned aren't they? Workin that laptop so i can get some actual valid data. Thanks for the response.

Mo_Bandy

yes they are canned aside from you can adjust your shift points up or down , so there is "some" flexbility.

Although it is a little pricey, the program LT1 edit will allow you total flexibility. in not only the tranny but the whole PCM. Sounds a little dangerous doesn't it... That is the software I use , then I log with Autotap however it is strictly an OBD II software.

I do believe like tunercat or one of the others will allow you to do your data runs with the OBD1 system.

Mo

Da Wiz

Hey Mo,

Can you believe it?? I found the problem. I was discussing the problem with a friend of mine the auto x's his ZR1. He has been an excellent resource for me, first time Vette owner. When i told him that even under WOT, the tranny still shifts at 4500 rpm. ( I didn't mention that in our earlier discussions, thought the comp was shifting on the downside of the torque curve :rolleyes: )

He thought about it for a second, and said it sounded like the comp wasn't sensing WOT. Maybe a bad TPS,,,,,OR,,,,,misadjusted?

I opended the hood in the parking lot at work, couldn't wait to get home. Had a friend depress the accellerator pedal to the floor, and what do you think I saw? The throttle body cam was no where near the upper mechanical stop.

I have a manual for a 93, loaner from my previously mentioned friend. the cable adjustment procedure for the throttle and cruise control cables wasn't quite right for my 94, but I got through it with a little horse sense.

What a difference!!!! So this is what 300+ ponies feel like when you let em run!!! I was thoroughly impressed before!, now I am completely stoked :D
Now I can actually use all of that 52mm throttle body I installed earlier this week. When I go WOT, she drops to second just as it should. Now the biggest problem I have is making sure I have enough open highway ahead of me to keep from being rude.....

Thanks for your earlier suggestions regarding LT1 Edit. I will lean heavily on that as soon as I get all of the mechanical issues resolved. Wouldn't want to try to compensate for mechanical flaws through the software. Can you imagine how far out of whack I could have gotten things?
:eek: :eek:

Thanks again, and I look forward to reading your posts. :cheers:

Mo_Bandy

Hey, thats great news!

Ah.. you didnt tell me about the TB exchange.. important info there.. LOL

Great..enjoy your new wheels :)

Mo