91 corvette LS swapped running a 4l60E and a 99 PCM.

I was doing some spirited driving this weekend. I got a CK eng light code P1810 and my car will surge above 73MPH. It feels like its trying to downshift.. I think its going in and out of lockup. I cleared the code and it did not come back but it is still surging.

 

I figured out the trans is in fact shifting in and out of lock up. I need to figure out why?

 

Check this link:

https://www.corvetteforum.com/tags.php?tag=p1810

 

Ch@Os, I have recently had a problem with my car that when I go over 65 mph and down hill my TC drops in and out about every 10-15 seconds... Your's seems to be doing the same thing but alot faster or more frequently then mine... I'll share with you what Pete K told me could be the problem with mine and maybe it can help solve your problem. .Pete builds racing transmissions so he knows what he's doing....He said when the switch on the brake pedel goes bad that sometimes it can cause the TC to kick in and out... I have purchased a new AC Delco brake switch #D852A on ebay for $15.00 and will put it in when I get a chance..Our switches are over 20 years old and can malfuntion internally causing a fluctuation of current which causes the in and out TC problem...He said if thats not the problem then to replace the (Lock up Solenoid) and the (4th gear Pressure Switch) in the transmission.. According to Pete either one of these can cause the same condition that we're having...The 2 parts for the trans are fairly cheap at around $10.00-$15.00 each and can be put in by any transmission shop pretty easy ..As a last cause Pete said to check the wiring , a bad place or short in the wiring can cause this problem ,this may be one of the first things for you to check since you just replaced the motor and may have damaged a wire. Im not much when it comes to electical so I may do this last if none of the other things work........Hope this helps you get it fixed buddy........WW

 

Thanks guys, the code keeps coming back so it may be a bad Pressure switch.Yesterday when I drove it home I pressed the brake a little and it went out of lock up and stopped surging. I was thinking maybe I will get a new valve body all the switches you mentioned WW.

It may have to wait until after Xmas I don't think my wife will be too happy with me spending money on it right now plus I want to do it right.

The trans was rebuild by my buddy but the valve body, switches and solenoids etc were reused. I want to buy a new valve body (maybe), pressure switch, all new solenoids, harness and put a shift kit in it. I want to do it right. That means its going to sit for a bit.

 

Check your brake light switch 1st.

 

WW was probably right, I really should, It is the simplest fix after all.

 

From what your saying about hitting the brake pedel and it stopping the unlocking and locking of the TC, it sounds like the brake switch may be the problem...Wouldn't it be nice if it was that easy to fix.........Here is the part you need . Damn , I paid way more then this for mine... Take your pick...If your wife says anything about $7.95 for the switch, let me know, I'll buy it and give it to you as a Christmas Present.........WW

http://www.ebay.com/itm/D852A-AC-DELCO-BRAKE-LIGHT-SWITCH-FITS-CHEVY-GMC-OLDS-BUICK-PONTIAC-CADILLAC-/360791312945?pt=Motors_Car_Truck_Parts_Accessories&hash=item5400d68a31&vxp=mtr#ht_1738wt_872.
.http://www.ebay.com/itm/ACDelco-D852A-Brake-Light-Switch/300750766770?rt=nc&_trksid=p2047675.m1851&_trkparms=aid%3D222002%26algo%3DSIC.FIT%26ao%3D1%26asc%3D163%26meid%3D2699917439364753089%26pid%3D100005%26prg%3D1088%26rk%3D2%26rkt%3D2%26sd%3D360791312945%26#ht_470wt_872.

 

I had that TCC problem once. A new brake light switch fixed it.

 

Not to hijack the thread, but im having some transmission problems myself
i have an 87 Z52 with a 700R4, at times when going downhill with my foot off the accelerator i can feel the transmission engage in a gear and disengage when it should just be coasting
also sometimes during WOT it shifts late, but other times it will be perfectly fine

What could be the cause of these issues?

 

Going downhill and having the trans go in and out of TC lockup is the exact same problem Im having, so the possible fixes in my post #4 above are the same ones for your problem.. If you can troubleshoot the problem thats the best way to go, but in this circumstance I have to start throwing parts at the problem because of my lack of electical knowledge...I would start by getting a new brake light switch like the ones I have posted above, these are cheap and could solve the problem... As far as your car shifting at a higher speed/rpm at WOT, that's what it's suppose to do... At WOT the car shouldn't even go into converter lockup....WW
.
.
.
.
.

 

I put a new switch in it and it did no good.
My next step is to order the TFP switch. The code keeps coming back.