Hello Bonne club,
Once again I have a question for all you gear heads, my car never goes into fourth gear. Ive verified this by, going a steady 65 miles per hour in D and then shifting down to third the RPMs only change by about 100. After that I accelerated to 80mph in third and then shifted up to 4th, the rpms instantly drop to about 1,300 at that point I coasted about 6-7 sec as soon as I touch the throttle the rpms are right back to 3rd gear proportions.

My symptoms are described in this post as well.(kinda makin me think 4th gear clutch hub shaft.) http://www.bonnevilleclub.com/forum/...75&highlight=A

I was wondering if anyone knows anything I can do to simply rule out or verify actual mechanical problem in the tranny, Or have I allready confirmed it?

I also would like to hear some opinions on the gm rebuild trannys. I was quoted $1,700 for a gm certified rebuild with a 3yr/100,000mi warranty.

Thank you

Are you sure thats not just the lockup that disengage at light 60mph acceleration and then reengage at 80mph , and make it look like you dont have a fourth gear?


just asking :?

edit: may be a lockup problem?

ok at any highway speed when I'm in drive if I manually shift to 3rd my rpms are allways identical.

As far as the lockup I have thougt that may also be the case. What besides the TPS needs to be checked for proper function?

My car does almost the same thing. When I accelerate the car stays in 3rd to long and shifts right into 5th at about 55mph, with a hard pull (not good). But hears the differance. Once in 5th, and crusing, to raise my speed by 15mph, I give the car a normal amount of gas, and it drops to 3rd instead of 4th. But if I slowly (slowly) ease into the gas, I can get it to drop into 4th.
So I know the 4th works, and all the gears shift smooth. I was encline to think it was a computer issue. Or a slight tranny adjustment. What do you guys think?

there is no fifth gear....our cars have a 4 speed

it has some kind of overdrive gear besides 4th. I can count them. I can manualy shift 1 through 3, put it in D (it shifts again) Then I almost let all the way off the gas, and it shifts/ drops down another 1000rpm. Same backwards. I can be coasting "in 5th", give it some gas, it will downshift, (into what I call 4th) then manually put it in 3rd, and it shifts yet again. Which means I went through two gears to get to 3rd. 3+2=5.
Maybe its not an actuall gear, maybe its some kind of spliter or something, but I can count 5 differant ratios. When I cruse at 70mph my rpm'* are at like 2000. If I manualy shift to 3rd, it goes up to like 4500- 5000. That is a huge jump. And it didn't use to do that. their was another shift point in their.

The lockup torque converter can almost seem like a shift when it locks up in third and then in 4th.

Ok With that solved, Why would the lock up in 4th all the sudden stop working? At least effectively. (remember I said I could get it to work sometimes. Is this going to eventually = a new tran? Is it strictly the converter that controls that "shift"? Can I replace it before it wreck my tran?

Just thinking, doesn't the lockup not happen until the motor is hot enough. It keeps the engine turning faster for quicker warmup. Is your motor heating up completely?

Does the heater put out air really hot after 8-10 minutes?

Engine temp sensor for computer may not be getting correct reading of temp and keeping lockup from happening.

There may be a code that keeps the lockup from happening as well. Who knows the algorithm for lockup occurring?

In order for you to be at 5000 RPMs at 70 mph you are going into second gear.

So, anyone have anything that might help me out? I have a bad problem, I am getting according to the DIC 14mpg and at $2.70 a gallon it'* ticking me off. Maybee someone can name off a few things I can check out. I would rather replace a sensor than a nearly 2grand tranny.