Transmission really slams into gear.

[Ryeguy]

Hey gang, quick question about the 700r4 in my '86. When I'm in park and I pull the lever into the "OD" position it really hits into gear pretty hard, in my opinion. If I'm on the right surface It even chirps the tires a little bit. It normally softens up a bit as the car warms up, but it's still firm. The idle is normal 6-700rpm or so. Is this a danger to anything? I asked a mechanic about it and he said with the corvette servo in the trans it might hit harder than you used to but if its not making noises don't worry about it.

Any opinions? Thanks!
Ryan

 

[boomdriver]

yes, the c-4 servo is bigger than the HD servo offered by GM as an upgrade. This trans is adjustable as well. The throttling cable can be moved in or out to soften/quicken the shift points and reduce the grab, or tightened up to stretch out the shift and make the trans feel harder, tighter.
At Idle it should have a slight clunk at it selects the gear, but not excessive. Its definately much harsher than any other domestic car. If its tight enough to chirp the tires even at idle, I'd guess that the previous owner may even have had a "shift kit" installed. I drove an old 79 T/A that would chirp the tires in every shift, like it or not, because of the kit that the owner installed. REALLY REALLY inconvenient when a cop was sitting nearby at stop lites...

You might want to look into it if its that tight. That will lead to increased tire wear as well as drive train. hard on the 6 U-joints.

 

[Ryeguy]

yes, the c-4 servo is bigger than the HD servo offered by GM as an upgrade. This trans is adjustable as well. The throttling cable can be moved in or out to soften/quicken the shift points and reduce the grab, or tightened up to stretch out the shift and make the trans feel harder, tighter.
At Idle it should have a slight clunk at it selects the gear, but not excessive. Its definately much harsher than any other domestic car. If its tight enough to chirp the tires even at idle, I'd guess that the previous owner may even have had a "shift kit" installed. I drove an old 79 T/A that would chirp the tires in every shift, like it or not, because of the kit that the owner installed. REALLY REALLY inconvenient when a cop was sitting nearby at stop lites...

You might want to look into it if its that tight. That will lead to increased tire wear as well as drive train. hard on the 6 U-joints.

Thanks for the input. I have it shifting great while I'm moving, but I am a little concerned about it going from park to drive hard... I'm not sure how to attack this problem though without loosening the converter or getting a new one.. I'll see what the trans specialist in town says. Thanks again.

 

[keremarsan]

Hi !

The throttle valve cable ( TV cable ) control line pressure in the transmission . If it hit hard, it must to be adjusted. Sometimes, it is not easy to find the right place to stop the adjustment system ( the TV cable passes from this adjuster ) . Imp : It is not natural that it hits so much , check aslo your shifting points , also partial and full detent downshifts , everything is normal ? because this high pressure will maybe cause also high shifting point.

For exemple : When light load ( just touch the throttle pedal ) , shifting from 1 to 2 gear on OD must be realized at 1200-1300 RPM when trans fluid cold, down to 1100-1200 RPM when trans fluid become hot. If your shift point is higher ( more then 1300 ) at light load, it is because the high line pressure in the tranasmission which must be corrected. Also the dowshifts must be affected , for exemple no dowshif from 3rd to 2nd even full throttle even the speed requires the downshift.

The cause can be a misadjusted TV cable or a worn TV cable. ... or also there is a spring - plunger inside the throttle valve body( inside the transmission , on hydraulic body , where the TV cable is connected ) , if the length of the spring is not normal ( longer then normal ) this can happens, or if the plunger stucks inside the throttle valve system ( inside the hydraulic body ) for different reason , it can happens also.

Begin with adjusting the TV cable as FSM ,

http://www.tvmadeez.com/article/index.php

http://www.patentstorm.us/patents/5727425/description.html

 

[Ryeguy]

Hi !

The throttle valve cable ( TV cable ) control line pressure in the transmission . If it hit hard, it must to be adjusted. Sometimes, it is not easy to find the right place to stop the adjustment system ( the TV cable passes from this adjuster ) . Imp : It is not natural that it hits so much , check aslo your shifting points , also partial and full detent downshifts , everything is normal ? because this high pressure will maybe cause also high shifting point.

For exemple : When light load ( just touch the throttle pedal ) , shifting from 1 to 2 gear on OD must be realized at 1200-1300 RPM when trans fluid cold, down to 1100-1200 RPM when trans fluid become hot. If your shift point is higher ( more then 1300 ) at light load, it is because the high line pressure in the tranasmission which must be corrected. Also the dowshifts must be affected , for exemple no dowshif from 3rd to 2nd even full throttle even the speed requires the downshift.

The cause can be a misadjusted TV cable or a worn TV cable. ... or also there is a spring - plunger inside the throttle valve body( inside the transmission , on hydraulic body , where the TV cable is connected ) , if the length of the spring is not normal ( longer then normal ) this can happens, or if the plunger stucks inside the throttle valve system ( inside the hydraulic body ) for different reason , it can happens also.

Begin with adjusting the TV cable as FSM ,

Bowtie Overdrives | TV Made EZ

Method for adjusting a throttle valve cable in an automatic transmission - US Patent 5727425 Description

Hello, thanks for the input. This weekend I will adjust the TV cable properly. About the shift points though.. When my car is cold and I'm on a level surface, if I just put it in OD and let the brake off the car will slowly pick up speed and shift into second gear on its own at a low RPM and cruise at about 12-14 mph.. without me even touching the throttle is this normal? My idle is usually about 700 rpm.

I've also noticed that at WOT my car wont upshift until I get off the gas a little bit. This might be due to the fact that my car only can reach 4,900 rpm as well.. which also has me stumped. Isn't the redline 5.5k? My car runs great, but what would keep it from revving higher than 4900 rpm?

Thanks

 

[minifridge1138]

Hello, thanks for the input. This weekend I will adjust the TV cable properly. About the shift points though.. When my car is cold and I'm on a level surface, if I just put it in OD and let the brake off the car will slowly pick up speed and shift into second gear on its own at a low RPM and cruise at about 12-14 mph.. without me even touching the throttle is this normal? My idle is usually about 700 rpm.

I've also noticed that at WOT my car wont upshift until I get off the gas a little bit. This might be due to the fact that my car only can reach 4,900 rpm as well.. which also has me stumped. Isn't the redline 5.5k? My car runs great, but what would keep it from revving higher than 4900 rpm?

Thanks

harsh shifts into gear are common in the 700R4.
My car actually drops 2 inches at rear bumper when I put it in drive.
Later years added a large pad to absorb the impact. The called it a dampener of some sort.
Lowering the idle can reduce the effect, but you don't have a carberutor so I don't know if that is easy or would bother the computer.
The TV cable controls shift points. You could have all in or all out and it would probably make little difference.
The car is supposed to downshift at wot, so having to let off to upshift is normal.
If you want to reset the tv cable, just squeeze the tab, slide the shaft with the notches all the way in, then floor the gas pedal. Engine off of course. it should pull the shaft out a bit. That is the factory setting. You are not supposed to adjust it after that.

Check your transmission mount. If it is broken, then the kick into gear will be worse.

As for your 4.9k max rpm. Is that under load or with the car in neutral?

Remember your engine is 22 years old. If it has worn, stock parts and you push it too hard you could break something.

 

[vetteboy86]

You may want to check play in the rear differential and U joints as well.

 

[keremarsan]

4900 RPM is NORMAL ! after 4750 , it is orange in some condition you can maybe see 5100 RPM but not so much, L98 is not designed to rev high RPM's , low RPM high torq is its speciality ),

Regarding your description, your car shifts correctly , more you accelerate, late it will upshift. NORMAL.

My car never upshifts on its own , I always must to touch it a little until 1000-1100 RPM when hot ...??! but I don't know if it indicates a problem

I had also some problem in 2007 after the overhaul of the trans so I read a lot about these trans but not sure about that ...

Good luck !

 

[Ryeguy]

harsh shifts into gear are common in the 700R4.
My car actually drops 2 inches at rear bumper when I put it in drive.
Later years added a large pad to absorb the impact. The called it a dampener of some sort.
Lowering the idle can reduce the effect, but you don't have a carberutor so I don't know if that is easy or would bother the computer.
The TV cable controls shift points. You could have all in or all out and it would probably make little difference.
The car is supposed to downshift at wot, so having to let off to upshift is normal.
If you want to reset the tv cable, just squeeze the tab, slide the shaft with the notches all the way in, then floor the gas pedal. Engine off of course. it should pull the shaft out a bit. That is the factory setting. You are not supposed to adjust it after that.

Check your transmission mount. If it is broken, then the kick into gear will be worse.

As for your 4.9k max rpm. Is that under load or with the car in neutral?

Remember your engine is 22 years old. If it has worn, stock parts and you push it too hard you could break something.

I'll check my trans mount this weekend.

That 4900 rpm max is under load. I don't mind that it peaks out there.. however I would like it to shift into the next gear so I don't have to let off the gas.

Thanks for the input all!