i have a 87 iroc-z 350 rebuilt 700r4 with shift kit i dont think my overdrive is working(it did work before). im driving down the road at 55-60mph and my tach is at 2850-3000rpm shouldnt it be lower? i had a troubleshooting code come on it was 24 (VSS) vehicle speed sensor could this be my problem? and is it a easy fix?

 

Please help

 

Any help please?? I can't afford the gas with it like this lol.

 

Have you even gotten under the car to look at the VSS?
I've had more than one of these things lose overdrive, but check the easy stuff first. Get a 10 mm wrench, loosen the thing, and pull it out and have a look. If no damage, reinstall.
On a related note, I had a '91 RS 305, all stock, 23 mpg highway. It lost overdrive. so, running around in third, still 23 mpg. Replaced the 700R-4 and installed a 3.42:1 rear, with correct speedometer setup. Still 23 mpg. And this isn't the only GM TBI vehicle I've had that wasn't sensitive to gearing.
But it sounds like you have 3.73:1 gears. Either way, try keeping it down to 60 mph or less until you get it solved.
If your speedometer is working, and you're getting the code, then the trouble may be in the dash, behind the speedo, or it may be in the computer.

 

it shifts through all 4 gears but the eletronic overdrive is not kicking in?? any suggestions? could it be a silonoid??

 

i have a 91 firebird with a 700r4 but it waits for the 4200 rpm to shift could my tranny be shot also when i hit the gas and lay off then hit it again it waits to pick speed up until it hits the point at where i left off before any suggestions thank you

 

My speedo don't work I think I need new instrument gauges would this cause my vss to throw a code? Is there any way to bypass it so I can have a switch for my overdrive lockup?

 

If you are feeling 4 shifts??? then everything is working. When the car goes into overdrive it will feellike a shift, when the convertor locks upit will feel like a shift. it sounds like a bad vss, buffer box(underdash by ecm yellow) or the tv is not adjusted properly or sticking which is a common problem with 700r4 trannies. Check that it is properly adjusted then check to see if its stuck, only way i know to fix the tv if is stuck is to drop the pan. Don't know if it coyuld be something else though.

overdrive working is not related to the gauges. it is a gear if the gear shift is put into OD it should go into overdrive above about 35mph. also the convertor uses a pressure switch to lock up this may not work if the vss is messed up but i doubt it. if the convertor is not locking up there is a way to wire in a switch to manually lock it do a search for that as its prety popular. summit also sell a kit for it.