dr76

Have a '95 LT1/4L60e (in a '76 Vette) that's not shifting properly. When shifting manually from 1st thru 4th, it will only go down to 2nd, then will only shift up to 3rd (no 1st or 4th). When put in OD/(4th) and allowing the tranny to shift, it goes into 1st briefly, then there's a harsh shift to 3rd, where it remains (no 2nd and no 4th).

My SES light does NOT come on, but when logging w/ DataMaster, I get a DTC 24 (DM's definition: "Low tranny speed"). I've replaced the VSS w/ a Delco unit and wiring seems fine (I had recently spliced into the VSS circuit [ckt 400] to send the signal to an AutoMeter Speedo, but have since bypassed the speedo and soldered the wire back (just to rule out the speedo))

Shouldn't such a problem illuminate the SES? What else can I do to ensure a good VSS signal to the PCM? The SM has some procedures (for DTC 24), but all involve having the half-shafts supported...I have nothing like this in my garage!

If anyone wants to see my DataMaster file...please reply / e-mail me.

* I'm using an F-body PCM / Painless wiring harness.

Thanks...I'm out of ideas!

Pro Built Automatics

You most likely broke the 2-4 band.

dr76

Well that's not I wanted to hear!

Is there a "sure-fire" test (w/o taking out the tranny!) to further ensure this is the problem, or from what I have described is it a "more-likely-than-not" situation???

Thanks for the reply (although depressing!)

Z28cross-fire

A good way to test if a band is broken or something is bringing it to a dealer. I brought mine in and they hooked a scantool to it and watched to see when the car was asking for 1st, 2nd, 3rd, and OD. It would be in first, ask for second but wouldn't shift, then ask for 3rd and shift, then ask for OD and wouldn't shift. It ended up being a broken 2-4 band. that is most likely what happened to you. sorry to say it but i also didn't want to hear it.

dr76

Z28,

Do I dare ask what the damage was ($$$)? I guess I need to swallow some pride and have it looked at...it's just that my car is such a "hybrid" ('76 Vette, '95 Vette LT1/4L60e, '95 F-body PCM, aftermarket wiring harness, fans, etc...), I really don't have confidence in many people.

Your situation does seem similar (if not exactly the same) as my situation is when I have it in 4th/OD. Did you try to shift it manually when this occured? Did it have 2nd or 4th then?

As stated in original post, I *DO* have 2nd gear (and not 1st) when manually shift, no 2nd when in "Auto-mode", and no 4th in either mode! I just wonder why it engages 2nd when I manually shift...???

Anyway, was just looking over my DataMaster file record-by-record, and noticed at the EXACT moment it shifts from 1st to 3rd (in 4th/OD) the following events occur:

Speed MPH goes from 2 MPH to 10 MPH
Force Motor (FM) Ref Amps goes from 0.92 to 0.16
Force Motor (FM) Act Amps goes from 0.94 to 0.18
TCC Duty Cycle (DC) goes from 0.00 to 90.19

I thought it was strange that ALL these occur w/in a 10th of a second. And why would the tranny shift to 3rd if it "thought" I was only going 2 MPH?

Aaarrrghhh...SO many questions

Z28cross-fire

Well i'll tell you something here going by my experience. I will never trust another dealer to work on my car. Infact i was reluctant to let them put in a new transmission. Especially when i heard the mechanic who was going to do it say, "yeah we just use chilton manuals." He didn't even take one out of a camaro before as far as i'm concerned. Then when i got it back they put a hole in my oil filter leaking oil all over the bottom, plus the back seal where the driveshaft goes into the tranny wasn't sealed right and had to be brought back. Needless to say i won't go to another dealer to have them fix my car, now i do everything myself. (actually the only thing the dealer has done was put the tranny in)

But now for the stuff that's important, your questions.

Money wise...i don't think you wanna know...but...here it is. The total with a new tranny and installation was $2300. that was $700 short of what i paid for the car.

As for the problems. Mine wouldn't shift into second manually (that's all i can shift to manually). Manual second was more like a neutral then a gear. Then about a month after that the 2-4 band gave out and i didn't have 2nd or OD. when floored it would bounce off the rev limiter in first and wouldn't shift out of it until i let off the gas. Then it would go straight to 3rd and stay there.

In your case i think it's the opposite of mine. You can shift manually into 2nd but won't have auto 2nd, as apposed to my no manual 2nd but auto 2nd. So that leads me to think you have a bad solenoid. It works like this...

1st gear...........solenoid 1 turns on
2nd gear..........solenoid 1 turns off and solenoid 2 turns on
3rd gear...........solenoid 1 and 2 are on
4th gear/OD.....Solenoid 1 and 2 are off (fail safe mode)

I believe that is right if not someone please correct me, i hate giving false info.

But, what i think is happening is when you manually shift, it gets enough power to unstick the 2 solenoid so it'll shift, but in auto mode it doesn't have enough pressure or power to shift the solenoid over. I'm thinking it's 50/50 that's the problem. I would bring it to a reputible transmission shop and have them look at the solenoids and check them out, if they're good then it's a band and you'll need a rebuild/new transmission.

Hope this really long post helps and i hope i'm not leading you in the wrong direction.

dr76

If anything, it's "Hopeful" information!

Yeah, I understand your perspective on dealing w/ dealerships. Although I don't have any Horror stories myself, friends/co-workers have told me things that have happened to them and it just makes me cringe!

I was paging thru the Service Manual in the Transmission sections and was trying to figure out all the solenoid functions, but wasn't confident I had a grasp on it...your summary above explained it so much better!

Thanks so much for the lession...I'm definitely looking further into the solenoid situation.

Z28cross-fire

Here's a picture that's similar to what the solenoid will look like. It'll be in the side of the valve body, which looks like the second picture. It's the first thing you see when you take the pan off the bottom, big and kind of looks like a brain. The solenoids will be around there and you should be able to replace them yourself. Also here is a link to a place that sells both shift solenoids for $39 http://www.transmissioncenter.net/4L60E.htm Just scroll down about 8/10th's of the way and you'll see pictures similar to what i posted.

Z28cross-fire

Valve body, i took this picture off that site i just posted for reference. It's the thing in the corner obviously, not the rods. Also changed the filter while you're at it, never hurts to spend another 10 dollars on that. But like i said, it is 50/50 that it is the solenoids. If it turns out it isn't then like the first guy said, it's a 2-4 band and it'll eventually give out completely. But i just like doing everything i can that's small and within my grasp before i do the whole thing, like a new transmission. Small things to do on your own that won't cost a ton are 1) get a new filter 2) get new solenoids. If it isn't them two then it's definitely something that needs to be rebuild.

Just had a thought: One reason it might shift into 3rd when it thinks it's going 2MPH is the solenoids. It might try to get into 1st, but ends up switching both of them, sending it to 3rd. Same for no auto mode 2nd, it's suppose to shift to 2nd, but doesn't because it'll end up switching both off. Then also it might not go into OD because it can't switch both off to "fail safe mode". If any of that makes any sense at all...

dr76

I agree 100%...I'd rather spend the $60 or so and try this myself then handing it over and saying, "it's broke, please fix it"! I'm sure there an honest shop somewhere here in S. FL, it's just that I haven't dealt w/ many shops, but will do research before bringing it somewhere (If I need to of course). I'm REALLY hoping it's the solenoids!

Thanks SO MUCH for the info, link, and pics!

I'll post again after replacing...

Dr76

dr76

Whew! Just replaced both solenoids and filter/gasket and all "seems" OK (knock on wood!)

Was definitely worth the 1/2 qt. of tranny fliud in my hair (and that's WITH a tranny drain plug!).

Dr76

Z28cross-fire

dr76,

Did the solenoids fix the tranny forsure then?

dr76

Yeah, so-far, so-good! Haven't had any problems since the solenoid swap.

This was SUCH a relief, especially since the car really has been babied. If the 2-4 band broke under the conditions it's been driven in, that would be quite sad, to say the least!

Thanks so much for the info you provided

Now if I run it at the track again someday (or purchase a G-Tech) THEN I'll understand if the 2-4 band takes a crap!

Z28cross-fire

Awesome! I'm glad that fixed it. It is always a relief to know $60 dollars fixed the problem instead of $2500. I also found out my solenoid actions were wrong

1st..... both are on
2nd.... 1 is off / 2 is on
3rd..... both are off
4th..... 1 is on / 2 is off

But glad to hear it!