ed's85irocz28

I have a 4 speed automatic overdrive transmission that will not go into 4th gear if I've got the gas pedal down, I have to leave off the gas for it to get into 4th. And when its in 4th, i can not give it more than about 1/3 gas pedal or it downshifts again.

I know some of these transmissions were made like that, but what do i have to get done for it to work like a regular automatic? I need it to go into 4th while the pedal is floored.

I've heard that 4th gear is weak in these transmissions, so what all has to be done?


Thanks
Ed

BBCAM

Sounds like you might have a 4th gear going out... or possibly your throttle valve cable is misadjusted, depending on milage I would bet the trans is on its way out as the early 700r4s were not really durable.. why do you want it to stay in 4th with it floored? that would be pretty hard on it unless you are moving at a good clip as 4th is overdrive it is not ment to stay in OD while floored the engine (in stock form) wont make enough torque so the trans is programed to downshift for more power in passing or high speed .. best bet is to have the trans checked by a competent shop good luck!

TraceZ

First - There is nothing wrong with your car. It is not supposed to stay in 4th gear whith the pedal past 1/2.

Second: This is for a good reason. The 4th gear in your transmission is not designed to handle the stress and power of full throttle.

Third: you can have a transmission shop install a shift kit and bypass the kick-down in 4th gear. I would suggest having them replace the 4th gear components as well with heavier duty parts so it doesnt fail under load.

I'd estimate the cost to be anywhere between $200 for a shift kit to $1800 for a complete rebuild with new clutches and parts. The "cheap solution" will most likely result in more expensive failures later, So I would recommend either doing nothing or getting a complete rebuild.

Why do you need to go so fast that you need 4th gear at full throttle? You're not looking for a darwin award, are you? Be carefull man.

teke184

try this

from the sounds of it you are describing the normal opperation of the trans.

ed's85irocz28

Thanks for the info.

I need to be able to go into 4th floored because of those damn ricers.....they'll want to race and most of them shut off around 120 or before, and i dont have enough to pass them with only 3 gears. And the other reason is because my friend told me about a drag strip not too far from here that has 1/2 mile races sometimes.

TraceZ

That will solve your problem for awhile, but it will also destroy your stock 4th gear in short order.

teke184

ok...something isn't right then

cause the factory rated top speed of the Z28 was upwards of 150mph...depending on the specific vehicle due to factory speed limiters.

are you saying you floor it from a low speed....hold it to the floor and you red line 3rd gear before you're going rediculously fast??

i was thinking that the auto Zs were capable of 140-150 without overdrive

BBCAM

Uhh ... no a factory mid 80s Z top speed is only around 100-120 tops, the computer will limit fuel before the car reaches much higher, plus if its a TPI car they run out of rpm around 4500 and dont make any power after that.. I have owned quite a few and work in a dealership and I haven't seen one go much faster than 125 .. even in the best conditions.

TraceZ

Correct. Back in the day, my 88 5.7 Iroc toped out at about 120-125 and it was in perfect running condition.

teke184

the late 80/early 90 third gens COULD do 150ish from the factory. MOST were limited with teh computer so that GM didn't have to put Z rated tires on them.

tell all these guys that they can't hit 140-150

i know i've read a comparison from the early 90s of the mustang and the 350TPI camaro...and they raced them on a oval track for top speed. and both were stock and very capable of obtaining 150mph speeds.

with the simple addition of a chip you can ditch the computer's speedlimiter...and hit 150.

it just takes a while with the poor breathing TPI

crash4cyl

yeah the thirdgen's suck when it comes to top speeds in a stock car. Now that 700-r4 kickdown should not hurt your trans at all. You were explaining a perfectly normal function of the trans as it was designed. I would install that kickdown kit, and tighten up your tv cable adjustment. This will allow you to go into 4th gear closer to full throttle, and up the shift firmness in all gear changes. Upping the firmness will also increase the life of your transmission. Then I would do a Shift kit on top of it and you should be able to bark 3 gears with the tv cable adjusted properly. From there the rebuild is in order. I would install a 'race kit'. I know a company out here that sells them for about $300 and a Sun shell for another $45. Plus the shift kit for $75. With all of this your trans should hold up to just about anything you want to throw at it short of a 1000hp motor. And you'll have neck snapping shifts and be able to run out any gear you'd like. If you do the strip version of the shift kit which will basically turn it into a manual valve body, then you can put it into whatever gear you want at whatever time. That's what I'd do if top speed racing is your goal.

Chris

BBCAM

I"ll bet the number of STOCK TPI 5.7 cars that could even hit 130 were so small you could never see one, I had a 88 5.7 TPI with bigger injectors 52mm throttle body and all the goodies and on an open deserted highway we only saw approx 127mph and throw in spedo inaccuracy and i'll bet it wasen't even that fast .. and that was with the stock 2.73 gears ..I have worked on ALOT of these cars and the top speeds were never as high as some Magazine storys would have you believe.. they are capable of those speeds but it takes much more than Z rated tires and a chip to get there.. the bonneville record for a stock class F body car (3rd gen ) I believe is only 172mph someone can correct me if im wrong ,but even my friends pro streeted 1000+ HP firebird only runs 8.89@ 148mph, of course its not optimized for top speed but just an example of what kind of HP it takes to go fast.. BTW I havent seen any HONDAS that are as fast as they think they are either...my big block 2nd gen has put quite a few in there place!!

ed's85irocz28

teke- if i hold it floored from a low speed 3rd gear hits 6000rpm at about 120. then i let off the gas so it can go into 4th, and hold the throttle at about 1/4 so it dosnt downshift again, and with 1/4 throttle i can get up to around 145 or so. (i'm not sure what it can get up to because my speedometer stops at 125, but it goes way past that because there's a big blank gap between 125 and some pin thats at the bottom of the speedometer...and it goes until the pin stops the speedometer needle.)

it also dosnt have a rev limiter or a speed limiter


crash- the tv cable sounds like a good idea to get tightened, and also the race kit and shift kit. I'll be getting about $350 soon so i'll look for those kits on ebay and try to find a deal to stretch my money. With those things you mentioned, would i still need to buy the kickdown kit in the link teke gave?



Maybe Christmas will help me out a little here, haha ....i'm only 17 and dont have my job anymore because of highschool wrestling....but i'm gonna try to get this all done.

BirchMan98z

lol you could always downgrade your gears to a 2.23 or something...