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1973 C10 "The Purple Truck"

Basic build
Overview Gallery Discussion
ktmoutfront said:
HHHMMM.

I am going to start on my 4L80E this weekend. But I was not going to crack it open as it has 1000 miles since a respectable shop did a rebuild and upgrade.
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That's why I didn't do any of this with the trans in the crew cab, it had recently been rebuilt. I did change the shift shaft.

In hindsight, I would have liked to have done the TransGo HD2 kit in the crew cab because of the dual feed for the 3rd gear clutch. But if the person that builds the 4l80e knows what they're doing, they can do it better internally anyway.
 
I was trying to figure out if maybe I have enough driveshafts laying around to put one together for temporary use after the trans swap. My thought was to measure the TH350 from the bellhousing to the center of the u-joint in the slip yoke., then measure the 4L80E from bellhousing to center of the fixed yoke, and use the difference to figure out about how long the driveshaft would need to be. The big surprise was the 2 measurements are exactly the same.

It doesn't really help because the 4l80 has a fixed yoke, so the shaft needs to have the slip built into it. I thought it was a pretty incredible coincidence. I even went out in the snow to measure the TH350 a second time to be sure.

I've been getting at least 1 thing done each day on the valve body so it will be ready to go for the weekend install. I don't have a ton of free time, but I figure getting a little done each day will help. Yesterday it was the pressure regulator valve. The TransGo kit reuses the valve, but replaces everything else. When I was watching a video they mentioned a new Sonnax valve https://www.sonnax.com/parts/1989-lube-regulated-pressure-regulator-valve. The part description says:
Sonnax lube regulated pressure regulator valve 34200-14K provides a significant increase in cooler flow under low RPM and high pressure conditions that benefits all vehicles, and eliminates the need for reprogramming '99-later vehicles with high EPC pressure at idle. The replacement pressure regulator valve has an encapsulated check valve that allows regulated flow to the converter charge/lube circuit at vehicle idle.

  • Check valve prevents converter or pump drainback
  • Improves converter release pressure
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That all sounded great to me, so I also replaced the valve while I was at it. In the picture below, you can see the holes added to the new valve.

20230228_143100.jpg

The next picture shows all of the stuff that gets changed out from the TransGo HD2 kit.

20230228_144020.jpg
 
One thing I should add to my length measurements. Even thought the transmission cases are within 1" length of each other, the crossmember has to be moved back about 6". The trans mount is a lot close to the end of the 4l80.
 
mrk5 said:
It doesn't really help because the 4l80 has a fixed yoke, so the shaft needs to have the slip built into it. I thought it was a pretty incredible coincidence. I even went out in the snow to measure the TH350 a second time to be sure.
Click to expand...

Some output shafts can accept either slip or fixed yoke, and it depends on the yoke. So you may be able to just get a 32 spline slip yoke and run it, as long as it has the proper slip and it doesn't bottom out.
 
Yeah, the fluid is an ugly color but it isn't burnt - yet. I figure in another 20K miles it might have been that way. I've drained all the fluid I can. Rolled the case over after I pulled the valve body to let the case drain. And I have a new converter. I'm not worried about it for how I'll be using it.
 
mrk5 said:
Yeah, the fluid is an ugly color but it isn't burnt - yet. I figure in another 20K miles it might have been that way. I've drained all the fluid I can. Rolled the case over after I pulled the valve body to let the case drain. And I have a new converter. I'm not worried about it for how I'll be using it.
Click to expand...
10-4, she was definitely ready for a blood transfusion.
 
Finished the valve body mods yesterday. Only item to note is the step on the bottom right, you have to cut the filter down to fit.

Screenshot_20230304_182829_Adobe Acrobat.jpg

That's not clear from the instructions but all the videos I watched talked about. None of them were super clear about how much to cut off. You need to cut the end off. Ends up being just enough to remove the closed off end.

Screenshot_20230304_183509_Gallery.jpg

Took 4 tries to get. 3 cuts and 1 final reassembly after forgetting the spring.

The internal harness I got had a few negative reviews saying it was too short. A little hard to tell from the pictures, but it's actually a little longer than the harness I took out.

20230304_114945.jpg

The plan was to install the 4l80e this weekend but when I started to reassemble the valve body I discovered the accumulator gasket is missing from my kit! :frown1:

Summit is working on sending me one. I also found one on RockAuto for less than $14 shipped that I went ahead and ordered.

Since I was at an impasse, I decided to wire wheel the outside of the trans.

20230304_151646.jpg

20230304_151715.jpg

Hopefully next weekend will work out.
 
It's in but it's all up in the parking brakes business. Any thoughts?

20230311_181629.jpg
 
Parking brake is not applied in that picture. Not sure if it would get better out worse.
 
You are going to have to get creative with shorter or longer tension rods and possibly different pivot points. Also try adjusting it out with a super deep socket/ratchet wrench on the long primary cable.
 
Pretty sure it will pull right into the pan when you set it. Like Ron was saying, going to have to reconfigure a bit. Or completely swap to the later style.
 
I had a similar issue and I just bent the rod on the passenger side down enough to make things clear. If it ends up touching while it's applied, that's not an issue since the truck won't be moving then.
 
Thanks for all the input. I'll mess with it today and see what I can figure out. I had just hooked it all up before calling it a day. Mostly because I didn't want to forget how it goes together. :rotfl: :doah:

I've never had operational parking brake before this truck, so I haven't messed with it. I park on a sloped driveway at home so I like having it.

Some more pictures. The new internal harness was from Rostra and it fit just fine.

20230310_154816.jpg

The only question I had was the connector for the EPC solenoid. The new one could go on either way. Luckily I took a picture of the original setup.

20230310_155807.jpg

Since the new connector has a blue wire instead of green, I did trace it back to the case plug to make sure they hadn't swapped the wires for some reason.

One of the trickiest things was getting the truck high enough to get the trans in and out on the jack. Since I was on my own, there was no chance I could muscle the 4l80 onto the jack under the truck. I needed 24" of clearance.

20230311_103926.jpg

The homemade stands are just safety backups. I also kept the ramps as far under the tires as I could. Just seen too many stories of guys getting crushed under their projects. I still had to tip the trans to get the top of the bellhousing under the exhaust.

A "new" versus old comparison.

20230311_142009.jpg

I did have a moment of frustration as I thought I was going to have to pull the exhaust because the 4l80 output yoke wasn't going to clear the crossover. Then I remembered what @folkenheath mentioned about the yoke being like a slip yoke I realized it should be easy to pull it quick. Sure enough, it is very much like a slip yoke.

20230311_181400.jpg

I like the fixed yoke better, but it is something to consider for someone else doing this swap.
 
Finished up the last bit of wiring. Connecting the Edelbrock trans controller (TCC) just requires a connection to the can bus plug on the PF4 harness. The TCC gets its power, RPM, and throttle position from that can bus. Downside is I have the Banks iDash connected to the can bus on the PF4 to give me engine info in the cab.

I noticed the TCC harness has a 2-pin connector in the same DTM style connector as the 4-pin connector on the PF4. However, the TCC instructions have no information about it. I posted on the PF4 forum and they said it was the same can bus signal. So I was able to connect the Banks iDash to that.

Screenshot_20230308_134028_Gallery.jpg

I still need to figure out how I want to tidy up all of the wiring, but this is everything connected up between the 2 controllers.

20230313_151238.jpg
 
I'm almost definitely going to need to do a gear change. 3.08 axle ratio isn't going to hold overdrive well, especially if it's windy or hilly. It runs just under 1700 RPM at 65mph.
 
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