Camper Special

[Mikel]

By the way, did any of you know that the TH400 found only in motor homes had straight cut gears that are stronger than normal TH400 gears? Since they are not helically cut, they make more noise.

If I remember correctly, the weakness is not in the gears, but in the thrust forces caused by the helical gears, which can crack the transmission case. Straight cut gears don't have those thrust forces.

[randyscycle]

I think you mean TH475. The TH425 was the front wheel drive version of the TH400 (Toronado, Eldorado...).

Ooooops! You got it.

[phoenix]

you are correct, it is actually the force pushing the gears apart that will crack the case and makes this trans stronger. I was not aware that GM actually gave it a different transmission number completely. as far as I know the gears are the only thing different in the whole trans.

[randyscycle]

as far as I know the gears are the only thing different in the whole trans.

That is correct. In fact when you rebuild a TH400 and want to strengthen it, that is a common modification, along with the heavier sprags they also used in the 475.

[loosewrenchcowboy]

That would be a TH425 then.

Oh, and loosewrench, check your measurements. I had to move the perches on the front Dana 60 inward toward the housing to make them fit the stock M715 springs.

randys-well, this is kinda strange. first, let me say i don't mean to sound argumentative (in case u thought i was, lol). anyways-maybe its the terminology we're using, lol. UNLESS-you used a ford axle possibly? i checked my measurements 3 times on the 725, and on 3 different axles. stock 91 dodge D60(dually), stock 93 dodge D60(single wheel), and the chevy(1980's) D60(single wheel) axles, all 3 are 32 1/2 inches, center to center-meaning from the center of the 1/2 hole in the middle of the passenger axle perch, to the center of the hole in the drivers side perch.
the 725 was 36 1/2 center to center.
OK, in the picture of your axle, on the passenger side, after you ground down the original spring perch, you welded on a new perch. in that picture i see the original center bolt hole that is cast into the diff housing. and your new perch is welded on closer to the kingpins. so wouldn't that mean you moved the new axle perch's out, toward the wheels from where the donor trucks springs were attached?

[loosewrenchcowboy]

That is correct. In fact when you rebuild a TH400 and want to strengthen it, that is a common modification, along with the heavier sprags they also used in the 475.

randys-don't mean to highjack the thread, but- i've only seen one th475. and i only know what is cause thats what the build sheet on the truck i pulled it from said it was(and there were 3 other identical trucks next to this oneat the junk yard). My th475 has a cast aluminum pan that incorporates the inspection cover too-meaning the trans pan goes all the way up to the engine and actually bolts to the motor as one piece. no seperate inspection cover to access the flex plate or converter bolts. the converter bolts are removed thru an access hole thru the motor-to-trans adapter. BTW-this was a Frito-Lay box truck with a 4bt cummins.
do you know of any other variations of this trans and were to find them? just the aforementioned motorhomes?
thanks

[randyscycle]

loosewrench,

In answer to both your posts:

First, if you go back and look at the pictures, I had to take about 1-1/2" off the center section (where the ring gear and pinion resides) to move the spring mount inward toward the center section. That meant that the front Dana 60 I used (from a full-size 1 ton Chevy truck) had perches that were too wide from the factory. I also moved the drivers side perch inward as well. That is why I used the term "inboard" This was on an unmodified, stock M715 that had its original closed knuckle D60. Nothing had been changed on this truck except the engine.

Second, If you had a 4BT equipped truck, it most likely had an SAE bellhousing, or adapter, regardless of which transmission it had behind it. It very well could have been a TH475, but I wouldn't assume all 475's had that pan configuration. I've seen 475's in motorhomes, Step Vans, P series chassis, School buses, Hi-Cube vans and a couple of GM station wagons, and even in a documented Chevelle, which I can only guess was either a special order, or got put in on the assembly line just 'cause. None of those had a factory alloy pan and some had a seperate alloy flywheel pan with the struts to the engine mounts and some did not.

[CHRIS UNGER]

So how is that radiator/innercooler install coming along and did you use the supports that go to the top of the frame for trans/tcase mount?

[Panther]

It haven't progressed that far yet. It's been frustrating in that work on the house has taken longer than expected and health issues have slowed me up. Nothing has happened since I dropped the engine on the frame and picked up the axles.

I only have another month in the garage so I have to get the axles under it and the engine at least mounted so I can move it out of there, should be interesting.

[Mikel]

Hey Lee,
Thanks for dropping off the transfer case
I think Bob has been trying to call you.