1992 Camaro Z28 with a 7004r (with Transgo shift-kit).

Recently I discovered that it doesn't want to shift to (I believe is overdrive) when I floor it; just goes into the redline).

I can shift into each gear without any problems

- Park = no problems
- Reverse = No problems
- DRIVE = No Problems
- Overdrive (D) = No Problems
- 2nd Gear = No Problems
- 1st Gear = No problems

They all appear to work fine. If I put it into DRIVE and then shift into (D), it successfully lowers the RPM's so that seems to work.

HOWEVER if I WOT, the tach just goes into the red and doesn't shift out 1 last time to decrease the RPM's like it used to.

WHAT can this be? A clutch? Pad? Throttle Linkage? or could this mean my Valve Body is GONE and needs replacing? (which I assume means I have to buy another shiftkit?)

The transmission was rebuilt twice already:

- Shift Kit
- Gasket and Seal set
- 9 Friction plates replaced (Kevlar)
- 9 Steal clutch plates were replaced
- Band H/D replaced
- Bushings replaced
- TV Valve replaced
- And a re-manufactured torque converter replaced

This was all done in 2006 (8 years ago)

What type of $$ are we looking at and what do you think is the problem?

Thanks

 

These cars never shifted from 3rd to 4th at WOT. You have to buy a corvette something or other to do it, I believe.

But 700r4's are notrious for the 2-3 shift being the first to fail when they go bad. So is it the 3-4 shift or the 2-3 shift?

 

http://www.joby.se/corvette/mods/2002-0X02_tranny_wot/

 

Somebody will have the correct answer. But on the track here in MN, my car will go ~115mph in 3rd gear, and just sit at like 5500rpm.

There is something preventing the shift, I don't believe anything is wrong with your tranny (besides not being able to use that 140mph speedo)

 

I'm not really sure which gear.

Basically I FLOOR IT.. It jets forward but it goes INTO the red before it shifts one last time. I have a shift kit so I can FEEL that last shift, plus you can see when the tach jumps back.

Before I BELIEVE it was around 4,500-5,000 when it had it's last shift once FLOORED the gas pedal. Now it's all the way into 7,000 for a few seconds before it finally shifts one last time.

The car is at the dealer and the transmission technition took the car out on the freeway with me in the passenger seat. And he says it's shifting normally except for the last and SUSPECTS that it might just be the TACH NEEDLE incorrect and so it looks like it's in the red..

I donno I don't see that being it.. But perhaps because it goes into the 7,000 fairly quickly..

 

Before this "problem" I woud floor it and it was get a shift early on that would just SHOVE you into the seat.. Now it GAINS SPEED but without that SHOVE on that shift (Shift 2 or 3?) not sure how to tell..

 

How fast are you going when this occurs?

 

I'm pretty sure you have your answer. The 700r4 won't go into 4th (OD) at WOT. It stays in 3rd bc that's the "power" gear. Why would you want the car to go into an overdrive gear (<1:1) at WOT. It won't benefit you.

If you're racing and you need to go faster, you need different gears. You will sacrifice grunt down low tho.

Basically you're running out of gear so your car is gear limited.

If you ran out of motor before it hit redline you'd be limited by your horsepower.

In reality, you need to gear your car so your peaking your engine right around redline in 3rd. That will be the best you can get from your car.

I have no idea what gear ratio you'd need. I put 3.70 in mine bc I want more down low grunt. It pegs in 3rd really early but I don't care about taking a 25 year old car much over 80!

 

Oh. And if you're experiencing problems with 1-2 or 2-3 it's something else. I'm just talking about the 700r4 and WOT going into OD.

If your 1-2 shift is now weak (I've never heard of a 1-2 in a 700 being weak) there could be other issues with your trans. My car will break loose on the 1-2 shift with little effort. Esp with the 3.70s.

 

Did any of you click on the link I supplied?

 

I don't think anyone did. Seems like a fairly straight forward way to "fix" it.

I'm not sure I would bother tho. It would make your engine work hard for little benefit being an OD gear.

 

Click on his link and you will have your answer. It is that simple.

IIRC the only 700r4 that would shift into OD with any more than 30% or so on the throttle was the B4C package, and even then it will drop out of OD at any more than 80% throttle.

I had to modify my tv plunger sleeve in order to Allow 100% WOT shifts into OD.

If your trans did it before, and doesnt do it now than you TV plunger sleeve was replaced with a stock one. Simple As that.

Click the link and you will have your answer.

 

It would not make the engine work any harder. The only difference is shifting into OD at WOT. That is it. It doesnt change anything else and it took me 5minutes to fill the rear 2 holes on the plunger sleeve. I just had to wait for the epoxy to set.

Now I get WOT 3-4 shifts. However, 4th gear is an overdrive gear so you wont really pick up an extra gear. Even at WOT in 4th at 110mph all it does is maintain speed with the pedal to the floor. You would need to change the gear ratio in 4th.

 

Well if it's not accelerating it won't. Holding speed won't make it work any harder but if you're not gaining anything, why bother? To drop a few hundred RPM? How long are you staying at WOT?

Like I said, I see no point to do this mod but whatever.

 

or more power....

 

Well yea if you WOT in 4th it will work as hard as WOT in 3rd. But once you realize you dont get that much pickup in 4th youll stop going WOT. Its a 1:1 gear, which means it doesnt have pull like 1st, 2nd, or 3rd. Thats why its called overdrive. Opening 4th up to WOT does NOT add any power to the engine. The transmission is a torque multiplier.

You will be able to go faster with a different gear ratio in 4th, but its not going to add power. Speed yes, power no.

 

I'm sorry... 4th is 0.70:1. No reason to use that gear for anything other than highway cruising.

If your car has more motor left when you redline in 3rd, you're rear end gear is too high.

For best performance your 1:1 gear (in this case 3rd) should be where your motor peaks out right at redline.

Top speed is generally achieved in your 1:1 gear. You can argue if you want but that's how it should be. OD gears are just that. Overdrive.

 

I did it before I learned that 4th wasnt anything other than OD. It was before I learned what I have on the 700r4. Now I am looking at changing the gear ratio to actually make it another gear to use with the turbo I am installing this weekend.

Pointless if you dont have a different gear ratio, Yes. But I did it cause I could and couldnt find ANY information to tell me I couldnt go faster in 4th. Now I have the experience to say, no it wont go any faster than it would without the mod.

 

My mistake, i thought 4th was 1:1. Thanks for the correction

 

To be at 6500 RPM in 3rd you need to be going 150mph assuming a 3.23 gear ratio. Even with a 3.73 ratio 130mph is 6300 RPM. I highly doubt you're going that fast.

The question is whether or not your tach is wrong. How fast is the indicated speed when you're doing this?

It sounds to me like it's downshifting into 2nd and slipping badly and finally shifting up into 3rd. Sounds like trans internal clutch problems to me and it has nothing to do with shifting into 4th at WOT because these cars never did that from teh factory and all that would do is slow your car down. Your car I think is going to a lower gear and slipping like crazy before upshifting.

60mph in 2nd gear is 4500 RPM. So if you're cruising at 40-60mph and you jump on the gas, it's going to downshift to 2nd. The 2nd-3rd shift is the one that usually fails, and it sounds like it downshifts to second and then cant quite find 3rd gear.

 

Sounds about right. I get 129 in 3rd with 3.73s. Takes a bit to get there but i got there, lol. Before I installed an aftermarket tach mine read 7000 at that speed.

Guess I need to get some 3.23s with the turbo

 

OK so I've come to the conclusion according to the description of what OVERDRIVE IS, I was WRONG in what I was describing.. So let me start over knowing this.

I believe it's gears 3 into 4 is the problem.

So basically if I am at a stand still [driving in OVERDRIVE "(D)" ] and I casually drive away, gears 1 -2 seems fine, 2 - 3 seems fine, and 3-4 seems fine. However if I am driving and I FLOOR IT, it shifts normally, but it REDLINES into 7,000 for approx 3-5 seconds BEFORE the tach jumps down (assuming that is gear 3 INTO 4). NEVER used to do that! I was NEVER in the RED when I floored it.. The tach just dials right into red with no stopping.

So I took it into my local Chevrolet Dealership and the transmission specialist of over 20 years takes the car out and gets into the freeway with me in the passenger seat.. We're doing like 80km/h and he FLOORS into and the tach needle continues into yellow and then into red.. if it removed his foot from the pedal it will shift. If he waits the 3-5 seconds (in red) it will then shift one last time. Course it's hard to get that much time on the freeway with cars around.

HERE IS THE CONCLUSION HE SAYS:

- There is NOTHING wrong with the transmission. The engine is working perfectly as well.
- He says the INSTRUMENT PANEL is the problem (tach to be more precise) and have removed it and already sent out for repairs. ($500)

NOW... I am UNABLE to understand what the tach needle has ANYTHING to do with shifting. Now I can understand if the needle is either NOT moving, or as he states it's moving too quickly into red when it's not actually anywhere near red... But HOW can the tach only do then when you FLOOR IT and it's going from 3 into 4th gear. How can the problem ONLY occur at that specific instance? I would THINK that if the tach is having issues rotating the needle the correct amount for acurate readings, that it would show for EVERY GEAR would it not?

And with a instrument panel sent out for repairs WITHOUT a car.. HOW can they possible fix it when they can't see what's happening during that SPECIFIC INSTANCE? It's not like the needle is NOT moving at all in which case that's easy to see and fix..

Am I being taken?

Thanks.

PS. I might be under the wrong assumption to WHICH gear as I am rather confused with the whole transmission gearing system ;-)

 

If OVERDRIVE means 4th gear and the car is not supposed to go into 4th at WOT (which that is what I've been reading), then perhaps I should mean 2 into 3? WHATEVER the last year would be that shifts at WOT. :-)

 

I think he's trying to take you for $500.

Just bc they have 20 years service doesn't mean they know or are honest.

I don't know what mine does at WOT if I'm going 80. 80 is fast enough for me in that car! If I want to go fast, I'll take this out...

 

92 tachs are notorious for reading high, so if you get on it and it buries the needle in the 7000 range something is off. You said it feels different, so Im assuming theres more to it than just the tach, but the tach is going to blur your symptoms.

The tach can be fixed with a soldering iron and $3. Do a search here. theres a guy here that will do it for $50-$70. Just requires cutting two legs off of a resistor block and bypassing it.

 

A lot of misleading info and some good info here.

In terms of gearing, I'm guessing you have the 3.23 gears. If you can drive at 70 mph (with stock tire size), and leave your car in DRIVE (not overdrive), your RPM's should read 3230 RPM......If you have the 2.73, the RPM's will read 2730 RPM.

The WOT 3-4 shift is a common question on this board. This occurs around 115-120 mph (aprox 200 kmh) with 3.23 gears. The way it works stock is that if you're at 66% or less throttle, you will get a shift into O/D. Imagine merging onto a highway. You're at less than 66% throttle. As soon as you ease off the gas pedal, the overdrive shift occurs.

The trouble of course is once you get to about 120 mph in overdrive, you're at 67% or higher throttle and it downshifts into 3rd gear. Conversely if you're in 3rd gear and have your foot to the floor, it won't make the shift to 4th. The result is the same either way. Your car will be in 3rd gear at 120 mph. This was done by GM because it's better for towing purposes (don't want to be in O/D with the gas pedal down while going up a hill for example) and because the transmissions are stronger in 3rd gear with their 1:1 ratio than they are in 4th gear with their 0.70 ratio.

B&M makes a TV plunger and sleeve that raises the 66% point to about 85% throttle before it locks out the WOT 3-4. This is somewhat good because it means you have less chance of the car shifting 4-3-4-3-4-3 when you're doing 90 mph on a winding road. On the throttle, off the throttle, on the throttle etc. But it means that instead of having the car downshift from 4th to 3rd at 120 mph, it now becomes about 135 mph. And that will send you waaaaay into the red zone. So I don't recommend the B&M TV plunger and sleeve.

The modified plunger that Twin_Turbo posted is the same design that Pro Built Automatics recommends. What this does is progressively raise the amount of throttle needed to make a downshift into 3rd as you raise in speed. This means at 50 mph, you need a bit more gas pedal to get the 4-3 downshift. At 70 mph, you need even more gas pedal to get the downshift. And once you pass 85 mph, the car WILL NOT downshift into 3rd unless you manually pull the lever down or else slow down enough that the car downshifts by itself (think 30 mph)......The other benefit is if you're in 3rd gear and WOT, the car will shift into 4th when you get to 5000 RPM.

The curious part of all this is that the early cars would make the WOT 3-4 shift stock (1987 and earlier). The 1988 cars got stronger transmissions, but they also put the TV sleeve with holes in it that prevents the WOT 3-4 and the downshift at 120 mph issue. Now at some point in the 1991/92 cars, GM started making them do the WOT 3-4 again. But I wouldn't put too much faith in the 91/92 cars doing it. Because after all, the 91/92 cars were also supposed to have baffled tanks like the 1LE cars. And some 91's and 92's have baffled tanks. And some don't.

The Twin_Turbo link above is the best of all worlds. It will let you shift into 4th at full throttle. It won't downshift you into the red zone. And it will allow high speed cruising (anything above 85 mph) without any chance of the car doing a 4-3-4-3 shift.

The B4C cop cars had sleeves like these. Because what good is a Camaro police car if it would top out in 3rd gear? Corvettes had the same tire size and similar axle ratios. But they would do 150-160 mph with the automatic. They achieve top speed in overdrive. Just like the 6 speed manual cars. They reach top speed in overdrive.

Now I see no way of "easily reaching" 7000 RPM in 3rd gear. You'd need one heck of a long stretch of road to do this. And I wouldn't trust the valvetrain to hold up to this unless you had heads/cam/Pro-Magnum/heavy duty springs etc. I suppose it could be a tach. But it sounds to me like a combination of you probably got a generic replacement TV valve/sleeve (with holes in it) and/or your transmission is slipping at the end of 3rd gear at WOT.