4L80E to TR400 Trans swap 1995 Chevy P30 chassis motorhome

[Supercharged111]

You've successfully beaten me almost all the way to the 4L80E. If you would though, lets perform a thought experiment. Forget about all the custom that has to happen for this swap for a moment, because my brother is handling all of that and could probably be a pro mechanic if he wasn't already a network engineer. But lets set all the custom aside and look at just the transmissions. Mechanically why would a TR400 be less reliable than a 4L80 with triple the miles? Nobody has explained that. Everyone is fixated on the fact that there's some custom fab, and wiring that has to take place, and the trans brace has to move and shortened driveshaft and so on. I'm really not trying to be a pain, I want to understand why. "it's newer" doesn't really explain anything

Because mileage isn't everything, you don't know if that 4L80 has had a refresh somewhere along the way, and they're not guaranteed dead or even almost dead at 250,000 miles. If it works it works. It's a stout box.

 

[Wulfdan]

Here's my final bit of advice - FIRST install the 4L80E, assuming it has the manual lever position sensor which is necessary to start the vehicle if you are still using the factory ECM to control the engine and transmission in that motorhome. If it works, great - run it for as long as you can while you start putting money aside for a refresh if/when the time comes. Like you said, you won't be putting a lot of miles but will be installing a much better transmission..There is literally no risk involved for you...If it doesn't work, you have the TH400 laying around which you can swap if you want to do so. Erik summarized the differences well, which is fine without getting into the weeds...We have all suggested this at least twice.

In my humble opinion, the 4L80E is the best transmission GM has ever produced and I say that with the caveat that I have not gotten my hands on any of the 10-speed units as of yet.

The 4L80E is the current transmission in the driveline. The motor went south, and I got a deal for a 454/TH400 with 70k miles. Me not knowing transmissions thought that more miles is bad, which sent me down this rabbit hole. Current plan after what I've learned in this thread is to drop the pan on the 4L80E and if there's nothing too bad I'll run it. Thank you for being patient with me. I don't know transmissions, they're a bit of a black box to me. That is why I reached out to people that know more about the subject than I do. I do like to understand why I should make x decision instead of y decision, which is why I ask so many questions.

 

[Schurkey]

In my humble opinion, the 4L80E is the best transmission GM has ever produced and I say that with the caveat that I have not gotten my hands on any of the 10-speed units as of yet.

I don't think your impression is going to change after you've played with a 10-speed. I'm reminded of Scotty.

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The only thing that compares to the 4L80E might be an Allison, but--correct me if I'm wrong--GM doesn't own Allison any more, so it's not a "GM" transmission.

 

[Medic0893]

Sorry I have to agree with the majority: if possible stick with the 4L80e. You said yourself it’s won’t be driven much. Even the high mileage isn’t reason enough to go backwards. Unless you purchased it from your grandmother a TH400 with 70k sounds like a magic bean (Jack). I’d put whatever $$ you planned for the conversion into having the 4L80 serviced and freshened up.

 

[udidwht]

The 94-95 454 TBI had fuel pressure of 26-32psi preferably 30psi. They also had different injectors. You sure it has the correct injectors in it?

 

[Wulfdan]

Yep I replaced the injectors with 454 sized injectors. Engine has a mechanical issue. Finally got it out and pulled the intake. Photos attached.

 

[skylark]

Yep I replaced the injectors with 454 sized injectors. Engine has a mechanical issue. Finally got it out and pulled the intake. Photos attached.

Who would've thought that someone would over rev a big a$s, under powered meth lab on wheels?

 

[Supercharged111]

Who would've thought that someone would over rev a big a$s, under powered meth lab on wheels?

Whoever it was must have been patient.

 

[Wulfdan]

Who would've thought that someone would over rev a big a$s, under powered meth lab on wheels?

I’m not sure what happened to it. I’ve never actually driven this thing on road. There was a rocket just hanging around under one of the valve covers, but I don’t know if that’s a cause or a result.

 

[NickTransmissions]

I’m not sure what happened to it. I’ve never actually driven this thing on road. There was a rocket just hanging around under one of the valve covers, but I don’t know if that’s a cause or a result.

My guess is somebody tried to launch the rocket, causing the damage. Question is why put a rocket or missile under the valve cover. I could think of many better locations on the vehicle to install such a system.

Damn meth heads...