nitricox

Is it ECU, or is it hydraulic? A few days ago, noticed a hard 1-2 shift in my stock 96 vette LT-1 with 4L60e. paying more attention, noticed that shift was delayed, then harsh -- and power real low when give more than about 1/4 throttle. checked fluid level, it was OK. Oh ... check engine light has been going on and off for about 6 months. Used to scan as bank 2 converter inefficient, but now scans as bank 1 converter inefficient!! Next day noticed shift delay getting longer and also noticed that water and tranny temps were abour 15 degrees F higher than normal. Then realized that power was back to normal. checked TPS connector and other connectors that are accessible, and all fuses. Can't access the connctor on the tranny (hey, its a Corvette, gotta sacrifice working room) so don't know if that's the problem. Now, temp is normal, car shifts delayed out of first, directly to third. and if downshift from 3d or upshift using "2" -- there is no drive at all in what should be second gear. Thinking this is all controlled by the ECU a/k/a ECM, i tried replacing with not one, but two used units with same service number. the replacements -- both of them -- allow the engine to start, but it cuts off after about 4-7 seconds..... runs out of gas. and yes, i tried swapping the PROMs (or what i assume are the proms in these ECUs. unplugged and re-plugged several times. same thing. put old ECU (which, incidentally, when opened has a trace -- Very faint -- burned smell -- not a good sign ) in, and engine runs, but tranny problem (with different PROM) remains. Scan for codes -- i get the same inefficient bank 1 converter. NO TRANNY CODES. oh, i put a vacuum guage on it to test for high back pressure in exhaust, just to make sure. its fine.
also, i checked with an almost no good Haynes auto tranny manual ... for the 700r (same tranny, but no electric solenoid except for TCC) and it shows that all of the bands and clutches and etc. that should be engaged in 2d gear are used in one or more other gears ..... all of which work fine. AND just pulled the pan for a look-see, and everything look OK, just some fine gook on the magnet and some fine powder in the bootom of the pan. Nothing out of the ordinary given the 126,000 miles on the car (and yes, i'm a sccmuck for not servicing the tranny .... i'm getting my due now! -- but at least i'm good about changing engine oil -- Castrol full synthetic.)
Am i barking up a wrong tree thinking its the ECU ?? In other words, all the parts eem to work, just seems to not be getting the signal.
Whatcha think? any input will be appreciated.

Smitty

2-4 band is gone,sounds like time to pull the tranny

nitricox

Thanks for a quick reply..... please take a look at my edit that i just posted. the queston is, if 2-4 band is gone, how come the other gears work just fine?

slow01z28

iTrader: (9)

I have the same problem with mine, No 2nd gear. everything look fine and the tranny builder said there maybe a small crack in the case or something didnt really get into.

So he got me a new case and rebuild the trans again. going to put the trans in on monday and see if that fixes the problem.

We did check the to see if it was the pcm and it check out fine.
So i would say to try and find a tranny builder near you and have him take a look at it.
But my guess is that the trans needs to be pulled and rebuild.

hope this helps

Rob

nitricox

Rob:
did all your other gears (except 2d) work ? if so, did yours shift from 1st (delayed) into third?
lemmeee know what happens tomorrow!
david

Automatics

If there is a "black" soot on the bottom of the pan that is away from the magnet, then the 2-4 band is most likely gone. The black soot is glazed band lining.

Smitty

There are other varibles that could cause no 2nd gear,but a excessively worn 2-4 band is the most likely,although usually this shows up in 4th gear also.Does the trans slip under heavy load in 4th gear?
In 2nd gear the 2-4 band is the only component that applys the achieve the shift.In 4th gear the 3-4 clutches apply also,which may help "cover up" a excessively worn band.
However,the transmission needs to be scanned to make sure its eletrical operation is normal,before moving on to possible hydraulic or mechanical failures.

Tony

nitricox

thanks to both of you for your thoughts. obviously, the car is what some people call "high mileage" .... but which i prefer to think of as proven depedability! so would expect some "soot" (friction material) in the pan. what was weird is that it started with a hard shift into second (not third) then within about a day transitioned into having no second. i haven't noticed it slipping in 4th, but will try it in a short while. years agp i had a second band go out in an borg-warner cast iron 3-speed in a 1968 AMX (#00149 for any AMX fans reading this!) and remember the gradual slipping when shifting, then lock into gear, then slip under load, then nada in second. but i would expect (as with the AMX) a good amount of fairly course metal from the drum being galled by the band sans friction material. NO transmission codes pulled in two scans. and the darn ECM smells a bit burned, remember?
PS: I rebuilt that old BW tranny (same as used by Ford (ugh!) in the 60's) and it lasted longer than the original!