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1st LS swap with new 4L60E that won't shift above 2nd gear
First time post, long time lurker here.
My dad and I just performed our first LS swap. It is a 5.3/4L60E out of a 2003 silverado into a 1957 3100 truck. We followed the wire harness instructions from www.lt1swap.com ti the letter. Had a broken injector wire and crossed b the O2 sensors but we fixed those and it runs great. Our issue was the tranny.
The tranny the motor came with looked god when we serviced it be for install. Fresh filter and fluid. Test drive it would shift 1-2 but then to neutral after 2nd. That was the case in drive and manually going through the gears. I called a trusted shop and was advised if it shifting then it's not electronic it most likely the 3-4 band which is a common thing.
We bit the bullet an purchased a freshly remanufacturered tranny and put it in yesterday only to have it do the same thing except it stays in second and does not go to neutral on
its own. So know we have a 57 that will do 80mph but it's in second gear. It also feels like it is starting from a stop in second like it won't down shift to 1st at a stop.
I think we have an electrical problem but being new at this its hard to figure out. We probed all the wires from the computer to the tranny and they have continuity. The only thing removed was the gear indicator switch. Fluid levels are good and new filter.
Anyone have any viable ideas on this issue?
Last edited by Fishnchipy; 11-12-2014 at 11:29 AM.
If it feels like it's starting out in 2nd gear and only shifting once, then it probably is. It will do this when there is no power to the transmission. Have you verified that you do have ignition power on the pink wire at the transmission plug?
We are using no tuners, all stock. We checked every wire to and from the computer and all are good. Grounds have continuity and hot leads are hot. I called the tranny shop and they said they get a bad solenoid every once in a while so its going back today and they will put it on the rack and check it for us. Crossing our fingers!
OK, went to the tranny shop. They hooked it up to the scanner and got a low VSS signal. The guy was able to shift the transmission with his scanner tool as we drove down the road so we know the transmission is good.
We had tapped into the VSS line to solder in a wire to run to the speedometer converter box which transfers the pulse into a mechanical rotation so we could keep the original speedometer. We were told to use the ABS output on the computer (port 49) to run the box so it would not draw off the VSS line. We did that and the speedo still works but the transmission still wont shift due to low VSS input from the computer to the transmission. We know the VSS is sending a signal to the computer since the ABS out is now running the speedo.
Any ideas on how to boost the VSS signal from the computer to the transmission?
If you disconnect the speedo box completely does the transmission shift correctly? I know a lot of gauge companies say to tap directly into the VSS wire coming off the speed sensor, but it generally causes interference problems. Usually you can hook up your speedometer (or in your case, the converter box) to the 'speedo out' wire from the PCM without any problems. If you are still having issues, I would double check the VSS wiring between the transmission and the PCM for continuity, maybe you have a broken/shorted wire or something.
That's what we did. The VSS goes straight into the computer now and the speedo box gets its signal from the ABS out from the ECM. I think we will check resistance in the wires to the trans tomorrow to see if we can track it down. Now we did have to add a resistor to the tach in order to make it work and boost the signal to that. Is there a way to do the same to the trans?
So you've checked the continuity between the trans and the PCM, and it's good? Did you check for continuity on those wires and ground to make sure they are not shorted to ground? I had a 3-2 shift solenoid wire short to ground and it put the car in limp mode and would start out in 2nd and go to 3rd and that was all. Wiggling the harness made the continuity to ground go away. I eventually replaced the whole wire and it fixed the problem.
Yes, wires are good to computer with no continuity to ground. The computer is getting the VSS signal since the computer is putting the signal back out to the speedometer box via port #50. The transmission tech was able to shift the gears on a road test with his handheld scanner via the OBD II port so we know the wire to the transmission are good. We are leaning towards a bad tune on the computer. We sent it to the guy who runs lt1swap.com. We sent him an email, now just waiting to see what he says I guess. We looked into a local guy here in Bakersfield and he wants $300 to put it on the dyno and set it up. If there is something internally wrong can it even be fixed or do we need to go get a ECM and start over?
Yeah, it does kind of seem like it's in the tune now, almost like it's not set up for a 4l60e. I would say the odds of the PCM being totally fried is going to be very low. See what Brenden says, he's usually pretty quick to get back to people, and if it's something he missed, he will make it right.
GOOD NEWS! I think we fixed it. We had all the power running from the battery and alternator through the stock 1957 amp meter in the original dash. The headlights started flashing and the amp meter was bouncing so we removed the headlights from the amp meter and only ran the accessories through it. Fired it up and behold it shifted while up in the air, all 4 gears and we think a TC lock up. Dad blew the PS hose again since he made it out of braided line which was only rated at 300 psi,,,LOL I told him to go down to the local hydraulic shop tomorrow and have a custom hose made since its a GM pump and Ford rack and pinion. He will get that made along with the AC lines crimped and all should be good. Thanks to all who have voiced their opinions and help diagnose this problem. Keep in mind, sometimes old stuff cant handle the new stuff! I will post again once we know for sure.
GOOD NEWS! I think we fixed it. We had all the power running from the battery and alternator through the stock 1957 amp meter in the original dash. The headlights started flashing and the amp meter was bouncing so we removed the headlights from the amp meter and only ran the accessories through it. Fired it up and behold it shifted while up in the air, all 4 gears and we think a TC lock up. Dad blew the PS hose again since he made it out of braided line which was only rated at 300 psi,,,LOL I told him to go down to the local hydraulic shop tomorrow and have a custom hose made since its a GM pump and Ford rack and pinion. He will get that made along with the AC lines crimped and all should be good. Thanks to all who have voiced their opinions and help diagnose this problem. Keep in mind, sometimes old stuff cant handle the new stuff! I will post again once we know for sure.
I wouldn't run anything through a 57 year old ammeter! Those things were a fire ready to happen when they were new, yet alone with the load of a lot of modern accessories. Sounds like you are getting it figured out though.
Finished it up today and went for a drive. All is good to go. Went through all the gears and even the TC locked up. I think we are all set. Dad said he will probably replace the instrument cluster with a new model that has AutoMeter gauges in it and this way avoid any further hassles with the old gauges. The old one has a bad fuel gauge and the crazy amp gauge. Thanks again for all those how threw in their two cents and tried to help.
Was a stock 1957 with a 283ci and three on the tree.
GOOD NEWS! I think we fixed it. We had all the power running from the battery and alternator through the stock 1957 amp meter in the original dash. The headlights started flashing and the amp meter was bouncing so we removed the headlights from the amp meter and only ran the accessories through it. Fired it up and behold it shifted while up in the air, all 4 gears and we think a TC lock up. Dad blew the PS hose again since he made it out of braided line which was only rated at 300 psi,,,LOL I told him to go down to the local hydraulic shop tomorrow and have a custom hose made since its a GM pump and Ford rack and pinion. He will get that made along with the AC lines crimped and all should be good. Thanks to all who have voiced their opinions and help diagnose this problem. Keep in mind, sometimes old stuff cant handle the new stuff! I will post again once we know for sure.
Here's my issue I did an ls swap and my trans is not shifting. I took it to the transmission shop and had it rebuilt only for them to tell me it's an wiring problem after the rebuild. Do you have any ideas what could be causing the problem
You cant diagnose a wiring problem over the internet. The wires going to the transmission all go to the PCM connectors, well, with the exception of the power to it which goes to the fuse box, so I would unhook the plug at the trans and the PCM connectors and start doing some continuity testing on all the wires. Check for continuity from end to end and also to ground to make sure nothing is shorted out. Good luck, wiring can be pretty intimidating, but those wires just go from plug to plug so it's as basic as it gets really.
11-12-2014, 08:07 AM
1st LS swap with new 4L60E that won't shift above 2nd gear 
