Turbo 475
 

Hey guys, I have found a turbo 475 at a wrecking yard, looks to be a unit from a motor home. I haven’t ever heard of the 475 before and thought it would be a more stout option Than a 400. I haven’t found a ton of information on them and wanting to get some insight wether or not it’s a good idea to buy and rebuild or not. Wanting to know what you guys think?

Any help is greatly appreciated.
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Re: Turbo 475
 

My understanding has been that the difference between
a standard TH400 and a TH475 is the TH475 has some
straight cut gears that are noisier and stronger and
that the TH475 has support for a tail-shaft e-brake.

I have seen more straight gears blown up than I have
the helical gears so I wouldn't get too hung up on it.
If you ever looked at the aftermarket gearsets for racing
you will find that they have more pinion gears but ALL of
them on the market are helical rather than straight,
despite the fact that straight gears are easier and cheaper
to make.
My guess is the factory went to straight gears in high load
applications to reduce thrust loading in the gear train,
rather than any inherent strength advantage of a straight gear.
Guys who build performance 400's simply rollerize the output,
making the thrust loading a non-issue.

Re: Turbo 475
 

GM built the TH475 to compete in the HD truck market. Where as the brand F C6 was strong enough from the factory.

Like you I scored one, but 25 years ago. At that time the average trans guy didn't know what could be done with it, and I traded it away for a TH400 core that I had built. I was using mine in a C10 I was building.

It is basically a HD version of a TH400, and lots of things can be done with them. Just besure to get rid of the TH475 converter which has no choices for performance. If that is your angle.

Re: Turbo 475
 

Not a guess brother.....The Straight Cut Carrier gears were solely to eliminate thrust loading, But not just on the Output Thrust, It also eliminated the thrust loads on the Pinion Washers as well.

Of course this means nothing in a HP build as you said.....Helical Cut Gears are naturally stronger because they have more Contact Surface Area.

Re: Turbo 475
 

GM had a true HD unit.....The Allison AT545 & was used in many GM Medium Duty trucks, Ford also used the AT545.

Motorhome 3500/350/30 chassis are considered Light Duty.

Re: Turbo 475
 

Is the AT545 similar to the AT542? I have the AT542 in my motorhome and the TC seems to have an incredible amount of slip in it.

Re: Turbo 475
 

Very similar as they are both members of the AT54x family. A lot of TC slip is normal.

Re: Turbo 475
 

Thanks for the input. I decided not to grab it
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Re: Turbo 475
 

I would have. GM hasn't built that trans in over 25 years. Good cores are getting hard to find

Re: Turbo 475
 

I would have, too. Spur cut gear trains sell for $200 each wholesale. Angle cut gear trains are an exact replacement, meaning the transmission could have been switched to a standard TH400 with a spur cut gear train left over to help cover the cost of the rebuild.

TH475s all had spur cut gears. All came in heavy duty applications. All tend to be noisy, but never have problems with gears cutting into the cages which is a problem in heavy duty applications. All are nothing more than a TH400 or TH375C with spur cut gears.

Re: Turbo 475
 

i have one from a 1982 motor home. 23k miles.

How do you remove the parking brake drum set up.

Re: Turbo 475
 

You need to fully disassemble the trans and change the output shaft and extension housing...

The 475 transmissions used straight cut planetary gear sets, the standard car units used helical gear sets,,,,these may need to be swapped over, just depends on the output shaft available...

Hope this helps...

:chevy::chevy::chevy:

Re: Turbo 475
 

I want to remove the drum and the back plate.

Re: Turbo 475
 

Remove the large nut & the flange.
The drum should slide off like a rear drum.
Than you can remove the bolts holding the backing plate to the rear housing.

Here is a youtube link that shows how...

https://www.youtube.com/watch?v=0q-p0CVL6nA

If you are looking to make this 475 a slip yoke car style trans, you need to change the entire output shaft which requires dismantling the trans.