How do I tell a TH475 from a TH400?

[OldSub]

I want a TH475 but don't know how to tell the difference from across the country.

I want to use the internals in a BOP case behind  Caddy 500 in my '54 GMC tow rig.

These are the photos I've been sent:





If there some question I should ask?  Or some detail in the pictures that should make it clear?

The price is right for a TH400 but shipping it across the country could make it expensive.

How do I know if its the right transmission?

Its a two-wheel-drive type and does not have the transmission brake I expected.   Two-wheel-drive is fine, but I wanted the tranny brakes.

[wayne petty]

this post answers your questions...

http://www.hotrodders.com/forum/gm-turbo400-475-trans-93088.html


but in the short read  i took...  you might want to think about using an adaptor plate.. and going with the full transmission...

[OldSub]

That was fun.  One of the reasons I posted this question here is knowing that Crosley would be one of those answering and knowing his answer would be the most complete and accurate.

Clearly not everyone agrees with my opinion of Crosley.

I've had misgivings about using the adapter.  Apparently I should reconsider.  It would sure be less work...

[wayne petty]

by the way...  there are a bunch of very expensive  heavy duty overdrives available.. all with chevy bolt patterns...

all shifted with the computer... which is probably what you want to stay away from...  but i could be wrong..

it will take me a while to find more ...

but they make 6L90E transmissions now.. i think in the HD configuration.

i have one question for the transmission master...

do the lower 4 mounting bolts between chevy and BOP transmissions line up..

i know they should as the multicase 350s were that way.. but it has been so long since i have seen one...

[OldSub]

I plan to use this truck to pull my trailer and will use it for little else.  That means most years it will travel less than 3,000 miles.  While the computer is part of that calculation, the gears and such are part of it too.

I've done the math two ways, Diesel versus gasoline and overdrive versus direct.  Unless the truck is so much fun to drive that it starts getting 15,000 to 20,000 miles a year neither the Diesel nor the OD really make any sense for me.

Besides I don't like the knocking and smell of the the Diesel and I do like the roar of a big V-8.  And I have to have a classic body,

If I can score a Gear Venders for $300 or something outrageously cheap like that I will sure reconsider, but based on new prices I don't see it making sense in my application.  And since most the time this truck is out of the yard I'll not be running OD anyway it makes little sense to pay for it.

That money can be parked in the retirement account buying me more time to play later on.

[Crosley.In.AZ]

lets  see,where to begin.

On hotrodders.com site  link.. the mouthy fellow is useless in my opinion. I do not care what GM calls HD in a t-400 type trans, 3L80HD. A 27 spline shaft is weaker than a 32 spline shaft.  I could have suspended him for his attacks- name calling  on me , but I did not.

Look at the photo i attached. The trans in question here  seems to have this pan on it.  As I recall these pans were special made for a Cummins engine trans plant into GM chassis motor homes to replace the weak 454.

t-475 with straight cut gear planets?  Take the trans apart is the only way to know for sure.  I would accept no other proof.  The trans is 30-40 yrs old and rebuilt once or 3 times and parts changed.

Another way  I take on high HP units with regular gear train, cut the front planet for a t-350 pump torrington bearing  between the 2 planets. ALso run a torrrington bearing at the rear of the case with a C6 bushing replacing the OE case t-400 bushing

[OldSub]

So it might be a TH475 but without taking it apart it can not be determined.  The seller says it came out of a 4Bt powered bread truck which argues it is the bigger trans, but still proves nothing.

If it were only hundreds and miles instead of thousands I might risk it, but its going to cost more to get it into my hands that the $100 he wants for the trans, plus he has quit responding to me so I suspect he knows its a 400 and doesn't want to admit it.

Thanks for the help guys!

I guess I'm still looking for a TH475 closer to home....

[58Apache]

Where is this located? I bought a TH400 to rebuild but after cleaning I am not sure I am happy with the case structure. I may stick with a manual tranny anyway. Now sure yet.

                         Steve

[OldSub]

He appears to be in Tennessee.

http://www.4btswaps.com/forum/showthread.php?13322-th475-and-adapter

I've backed away since I've had so much trouble getting questions answered, including those sent PM and email.  Since he is answering some other guy's questions I expect he didn't like some of my questions.

I still want a TH475 but if I don't find one soon I'll drop back to a TH400 since I have several on hand.

[58 Yeoman]

Here's a 400 in East Peoria, IL. for $250, with a trans brake.

On Craigslist.

I have a 400 turbo transmission with a locking brake on the back. It came out of a chevy box truck and has only 40,000 miles on it after the rebuild. Great condition. Call me at 309-635-0296

[Crosley.In.AZ]

Here's a 400 in East Peoria, IL. for $250, with a trans brake.

On Craigslist.

I have a 400 turbo transmission with a locking brake on the back. It came out of a chevy box truck and has only 40,000 miles on it after the rebuild. Great condition.

the possibility of that trans being a t-475 is higher with the parking brake on the back of the trans.  that design brake was used in large motor homes, heavy chassis like the  box vans - etc

During a rebuild I have replaced burned up straight cut gear planets with angled cut planets.  I still advise a look see to verify straight cut gears.  these style planets are getting hard to locate

[wayne petty]

what about the needle bearing th350/ th400  conversions that i have heard about over the years...  

i have never seen one in person..  do they really exist...

[Crosley.In.AZ]

what about the needle bearing th350/ th400  conversions that i have heard about over the years...  

i have never seen one in person..  do they really exist...

I am not sure I understand the question.

A t-350 pump torrington bearing is a common size used for several applications where a thrust washer is replaced.  Between the two planets as the photos indicate

Also at the rear of the t-400 case a bushing from C6 pump and a t-350 torrington bearing work to smooth out wear and HP loss.

Very common HP mod to add bearings in place of thrust washers.

There are also roller bearings adapted to rotating shafts  in various trans

[Beck]

The original transmission in question does have the Cummins conversion oil pan. These were used on Chevy P-30 step van conversions. Frito-Lay was one of the major purchasers. Cummins designed this conversion to use the 4bt motor with the 475 transmission. I have the 4bt and 475 in my '62 Chevy truck. The 475 used with the diesel engine does not have a vacuum setup for kick down. The diesel has a turbo so there was never any vacuum in the Cummins application. There is a mechanical screw adapter in the modulator location. The shift is controlled by this screw location therefore is not dependent on motor load. You would have to change this for a gas motor. I do not notice any extra gear noise with the straight cut gears, but the diesel niose may be covering that up. If there is a torque converter included it will not work with the gas motor either.

If you are looking for a 475 like this the 4btswap site would be a good location. I was a regular there when building my truck. Those guys are wanting to put OD setups behind the motors since rpm is limited. Most of the GM/Cummins conversions used the 475. These transmissions have been pulling step vans around for many a mile and rebuild. Mileage could be very high.