I installed a Transgo shift kit and no longer have high gear. I also changed the transmission modulator, pretty sure the old one was pulling in trans fluid into the engine. It was used but good when used last. I ordered a new US made replacement. The line is connected and braided thick wall. I even replaced one kinked cooler line. The pan was full of crud dying behind a 403. Any thoughts ate appreciated.

 

I was thinking one or the other item(s): (1) Modulator or (2) Incorrect throttle cable adjustment. I did find what appears to be a pretty decent conversation you might consider - 70'sForever appears pretty knowledgeable w/ some discussion regarding shift kit.
https://www.chevelles.com/threads/th...rd-gear.79100/

 

Thanks, those were my thoughts as well. Since I have SEFI, I have an aftermarket bracket, it criss crosses over. I have an adjustable TV, backed it off but will actually unhook it and go for a drive. I only need this POS to work for a year to save for the 5 speed swap.

 

TV cable did nothing.

 

The TH350 doesn't have a TV cable. All the cable does is make a forced downshift and increase line pressure. You can run the TH350 without the cable however you will have to manually downshift.

 

Did you replace any pistons or spool valves from the Trans-Go kit ? If you did, put the originals back in to see if that works.

 

Yes, kick down cable, used to messing with a 2004R trans.

 

I will look in the box and see. I did the base kit tune. This trans had super soft shifts before the kit. They are only normal now, far from firm. I am not a fan of the TH350 and this one isn't changing my mind.

 

Does it have reverse?

Go back and double check the transfer plate at the front of the transmission. Make absolutely sure the spacer plate, transfer plate, and support are in the correct order.

While the pan is off, make sure the kickdown linkage goes back to its normal resting spot.

Make sure the valves in the valve body are free to move, and snap back to their original resting spot with authority. If they don’t snsp back, more than likely you raised a burr when removing/installing valves, or there is debris jamming things up.

If you don’t see anything obvious, call TransGo tech support. I have talked with Dave and Glenn over the years, both of them are very knowledgeable.

 

As stated, check the transfer plate, I have seen the one from the kit installed on THM-350's without putting the stock plate back over this. Without the stock plate covering the kit plate which has the slots and passages, it cancels out reverse and high because all the fluid pressure gets instantly dumped back into the pan. I may be wrong but I think the purpose of the shift kit plate is to double-feed the reverse/high clutch. This is done by the slots in it, sealed up by the stock plate. In other words, the kit plate is sandwiched between the stock plate and valve body. Hope this helps along with the advice of others.

 

Yes, reverse works fine.

 

that’s exactly the purpose of the transfer plate. If you study the hydraulic charts you will see that the direct drum is split into 2 separate chambers. One chamber is used in high gear, both in reverse. By removing the seal that separates them, and blocking off the reverse feed, you basically double the clamping force on the clutches.

Most people omit the seal and block the feed hole during an overhaul. It’s a much better way to do it. Unfortunately, it requires transmission removal and teardown. The shift kit and transfer plate is an easier way to accomplish the dual feed.

If it had 3rd gear before the shift kit, more than likely it’s something you did during the installation. Did you put the gaskets in the correct spot? Springs installed correctly?

 

Yes, pretty sure on both. I will let you know on the vacuum modulator. I did change that with a used one at the same time. It may have gone bad, was Ok. I didn't remove the spring for thr modulator. I did go back in the replace the check *****, missed that. Thought it was all correct. All other gears work normally, just no third. Will see after I get the new modulator installed, nothing comes quickly up here.

 

Replaced the modulator and even reinstalled the factory steel line, still no third. I think it had 3rd before installing the shift kit, the 403 had low oil pressure, even after installing new rod bearings, so I drove it on the highway maybe once last year. As I said, plenty of crap in the pan but the one two and reverse is normal. I will drop the valve body and go through everything again.

 

I am going to make sure that 2-3 shift valve isn't binding, pretty straight foward to install and not really much to this shift kit. I have done a few of their 2004R which are much more complicated.