Manual valve body on a 4L80e?

[Gregsch]

I think my TH475 is about to die. Looking at options... Ran across some info on the web about hot rodders using manual valve bodies in street cars. I have always wanted an overdrive so I can keep up with traffic. With a manual valve body in a 4L80e i could have overdrive without going to a computerized engine. Could be kinda cool to have full control of the shifts. Anyone have any experience with such an animal?

[bkahler]

Greg,

I vaguely remember a few years back that someone went down this path. It might be worth a search.

You could also buy a stand-a-lone controller.

All they need for inputs are throttle position and speed.

[Keyair]

If you don’t have the transmission yet, look for a 4L85e. It’s the modern equivalent of the Th475. It has the same straight cut planetaries. It’s is rated at 16,500lb, and up to 22,500 towing. The 4L80e is 8,000lb.
It is my understanding that the manual valve body box is cheap but very harsh in operation.
I think Mel has lots of experience with the 4L transmissions.... not all of it good!

[waynebrv]

I have the TH 475 behind a 4BT Cummins in my 1968 Bronco. Yes, it fits and is a hoot to drive.
I too have been looking at putting the 4L80/4L85 but with a throttle controller in the Bronco. The controller will control the shift, provide lock up when desired just fine.
My only issue is that the 4L80 is 2" longer than the TH475 and this will require me to shorten my rear drive shaft and lengthen my front shaft. Secondly, I have yet to get validation the adapter from TH475 to my Dana 20 will work, although anecdotal evidence is that it will.
I built this rig in 2004, but was so disappointed I did not get 30MPG. I did get 26MPG and found it easy to get 22-23 local hossing this lil Bronco around.
For most pickups and RV chassis, where 2" is not a show stopper, the 4L80 is a great choice.

Wayne

[waynebrv]

Several vendors make controllers that will make the 4L80 shift by throttle pressure and by RPM. Or both. Many of these controllers do not require a computer to do the initial set up, all the adjustments are by the seat of the pants judgment and by on board read out on the controller.
For the most part, the swap is remove and replace, with the exception the drive shaft length. If the unit has a sliding shaft and bearing cradle right behind the tranny, a few feet back, many times 2" is made up in slide and spline.

Wayne

[waynebrv]

Here is a URL, and 13 post down, there is a chart on 4L80 output shaft lengths. You may figure out what length shaft and adapter is on your Th475, and just order the 4L80 with the shaft and adapter to fit, and its a remove and replace.
https://www.pirate4x4.com/forum/chev...e-2wd-4wd.html

[Keyair]

Don’t forget, you will need a tailhousing mounted parking brake too.

[bkahler]

Having just gone through the process of installing a 4L80e in my Argosy motorhome I can say depending on the installation things can get interesting pretty quickly. Keyair is correct about making sure you have the drum brake assembly for your motorhome.

My installation was probably a little different than most of the motorhome installations in that I did not need the tail shaft mounted drum parking brake. My rear brakes are drums so my coach had the typical brake cable that ran from the drum to the lever/foot pedal under the dash. In some respects that made for an easy installation. The difficult part was finding a tail shaft yoke that would work. For non drum brake, non sliding yoke installations you need a fixed yoke setup. I didn't have that and had to scramble to find parts that would work. One of which was to have a custom fabricated spacer bushing (Mel's method) to force the yoke to be in a fixed position instead of sliding. I spent a few nervous weeks worrying that I would have to remove the transmission and send it back to the shop to have the tail shaft reworked. Fortunately after reading Mel's thread I was able to come up with a workable solution.

Once I managed to get a fixed yoke I then had the front drive shaft shortened a couple of inches and everything bolted up nicely. I did have to move the transmission mount rearwards about 2-3/8" or so. Not easy due to how Airstream built on top of P30 chassis but doable!

Brad

[Gregsch]

I have been following up on all the great advice I have gotten . Thanks !
In my search for a 4L80e or 4L85e I stumbled across a used TH400 out of a 1984 p-30.
This may be a short term fix for my problem. Football season is well underway and I don't want to miss a game due to a breakdown.
My question is... the trans I found has the parking brake on the back of the transmission. My 240 has the parking brake on the drum brakes on the rear axle. What is involved making this swap?

[Isuzusweet]

I would also look at taking the TH475 into a good hot rod transmission shop and see how much beefing up the original transmission would cost (I've heard that you can get beefed up clutches, bands and torque converters). Another option would be to put a Gear Vendors behind the transmission for reduced highway rpm.

Below blurb came off the net.

The 475 came into use in '71 and was used in motor homes, buses and 1-2 ton trucks. The main difference is the use of straight cut gears in the planetarys. The gears are stronger but a bit noiser. I haven't heard of lower 1st gears as stock but aftermarket has them. Also clutch packs can be upped to six discs in certain cases but I can't see this being necessary if the tranny can handle a 2-ton truck with a GVW of 10,000 lbs.

Keeping computers out of our beast is not such a bad thing, IMHO.

Cheers
Sidekick Tony

[martin300662]

If you are going the route of having something standard beefed up, what at 700r4. They are an overdrive box without electronic control, and although aren't designed for a 10,000lb vehicle but can be beefed up in the same way that the TH400 is turned into the TH475.