dakleenupman

Hey all. I have a 700R4 that will upshift 4 times but will not engage lockup. I recently put in a 3:73 gear and my rpms at cruising speed (70mph) are about 3000. That can not be right. Myquestions are:

1) How will I know if my trans has a lockup converter
2) If it does, what controls the lockup

I would assume GM would have used a lockup as the trans was replaced 2 years ago by GM.

Any help would be great!

Chris

dakleenupman

Lets send this up again and see if anyone has the smarts to figure this one out,

Chris

rjt76

sounds like 3000 is way to high for 70 mph with 3.73. i am at 2100 at about 60 with my 3.73..... somthing
is wrong for sure.

Floor guy

Use a scanner to see if the ecm is commanding the lock up. If yes, it could be a solenoid, torque converter, wiring issue to or in the trans. Defective pressure switch in the valvebody. Solenoid is the #1 reason for no lock up. I do not recommend swapping parts though. Troubleshoot it using the helms manual.

87zjeff

iTrader: (4)

i have a 3.27 rear end and i tiurn 2000rpms at 60 mph. with a 3.73, i would think the rpms would be significantly higher. at 70 mph i am turning 2500rpms. so 3000rpms for a 3.73 should be about right i would think. disconnect the electrical connector at the transmission and see if it still shifts 4 times. with a 700r4 you will only have 3 shifts if you don't count the lock-up.

honken

You have a switch at the breakpedal that control the tcc
Can be the same as the breakligth switch with (4 kables instead off 2).or a separate swith.Its give the signal to the ecm.
If it dosenth work then the tcc dont engage.
If you drive and have hit the speed its engage tcc try to press the
breakpedal up and see if it engage (maybe need to be adjusted).
The vss signal tells when to engage (mph).

(Toth it hade 4 gears and lock-up??)


Mybe it helps.

rjt76

there is a calculator on the main page that will figure this stuff out for you guys. I just did it for my setup and came back with a 700r4 tranny with 3.73 gearing while cruising in overdrive 2100rpm =61mph. I have 245 50 16 inch tires also.

3000 rpm with 3.73 gears= 87mph while driving in overdrive.

something is definately wrong with your calculations....

your converter maybe is slipping?? or your not in overdrive or you dont have a 700r4 tranny?????

87zjeff

iTrader: (4)

dan, this might be a pain in the ***, but you might want to remove your rear end cover and count some teeth. the calculations say you have a 3.23 rear end. where did you get the rear end? also, did you change your speedo gears in the tranny when you put in this new rear end? if not, then that could explain a big part of the problem. speedo gears would definitely be different. i'm running all stock ratios and and tire sizes. the rpm calculator and mph calculator on the main page are consistent with what i have.

dakleenupman

Ok, let me rephrase this. I get upshifts to 4th gear, not 4 times. Sorry for the confusion. I agree with rjt76 regarding the calculations so that must mean something is wrong. As far as the scanner, for whatever reason, my ECM will not communicate aith the 9045 Actron scanner. I do not have access to any other at the moment so that's out. I will try the pedal up thing. I can tell you my VSS on the back of my speedo was bad which caused all sorts of runability issues but I have since replaced that and now mostly all is fixed but still no O/D.

87zjeff

iTrader: (4)

4th gear is overdrive on the 700r4. did you change the speedo gears in the transmission itself? if not, that is most likely your problem. even if you have an electronic speed sensor in the transmission instead of the speedometer, the ecm has to be changed to realize the new rear end ratio. it cannot sense what gear you have back there.

dakleenupman

Yes but lock up comes from speed. At 40mph stock, it should lock up. My gear ratio cahnge in the rear has me getting to 40mph faster (even though it is really about 35mph) so it should lock up sooner.

87zjeff

iTrader: (4)

and it probably does and you aren't feeling it. especially if the trans is stock. the only way to know for sure is to unplug the connector at the trans and see if it makes a difference. but that is not your big concern. lock-up only makes a 100-200rpm difference. not enough to explain 70 mph at 3000rpms. i think your speedometer is off because of the rear end change. when you are doing 70mph, are you just barely passing traffic or are you blowing it away?

dakleenupman

OMG!!!!

I can't believe it!!

This WAS the problem all along!! I tried it as you said, driving along tin top gear and lifted the brake pedal up toward me and BAM!! there was lock-up.

Now all I need to do is figure out how to adjust it. Any ideas there?

honken-----------------------you are the GREATEST!! Thank you........

Chris

dakleenupman

Well, considering my speedo is off due to the gear swap, my real 70 mph is like 85 on the speedo and I am just barely passing them. I had someone pace me to get exact readings and sure enough, I was at 50 when my speedo said 62 and no lock- up.

When i did as above, I noticed a 500-700 drop in RPM. Enough to make me feel better and get better mileage..

Thank you though for you efforts in this problem. It always is helpful when a fresh set of eyes gets involved........

Chris

honken

Glade its not a big broblem.
The switch sits behinde the preakpedal(with the breakligth switch
or the same switch).
turne it in to the pedalarm(you have it to far from the pedalarm).
The lock-up gives up to 30% les rpm.

dakleenupman

You ROCK!! Thanks again..............

Chris

BigWhiteGTP

Could this be linked to why my car hits the rev limiter at 110 instead of the stock setting of 125mph? Or not? Maybe the ecm thinks it's at 125, but the car is only at 110?

My car won't go past 110, I tried to gently hit 110 and still I get those 3-rapid angry revs.

honken

Does the gauges showe 110 mph or 125 mph if the gauge showes 125 yes if its 110 now.
You have a rev limit to?

If you haved 3.23 gear and but in a 3.73 gear you will get wrong readings off speddo(goinge slower than its showes with higher rpm).


You can calculate your mph vs gear here.

https://www.thirdgen.org/newdesign/t...ulations.shtml

Hope it help??

dakleenupman

I'm thinking if your speedo shows 125, the factory speed limiter will shut it down EVEN THOUGH you may only be going 110. That is because the ECM gets its signal from the VSS (vehicle speed sensor). Get the gear for the speedo changed to the correct one if you changed your rear end gears to a higher gear (ex: 3:08 to 3:73), like I need to do, and all should be good.
BTW: what tpye of model is it? If it came factory with H rated tires or higher, it should be governed at 125 as H rated are good to 126 I think.

Chris

honker---------- have I told you that your are the best!! I adjusted the switch (I have 2) and it works just like it should now!!

BigWhiteGTP

I have 2.73 gears. As far as I can tell, the speedo is correct. Now the car did come from the factory with 215/60r16 pizza cutters.

dakleenupman

My guess then is 110 is where the limiter is set to.