Technical TH475 slip yoke conversion

In my 1959 Chevy apache build, we've gotten our hands on a th475 transmission with 27k miles. It came out of a 1984 Southwind motorhome and has the ebrake on the drive shaft.

What does it take to convert it into a slip yoke transmission?

As of now the ebrake and bolted yoke have been removed. I've confirmed the output shaft length is the short 4 in one. This does have the roller bearing extension housing so it will be swapped for a new standard bushing extension housing.

Should I get any slip yoke with 31 teeth (32 with the one missing), remove the output shaft o-ring, and call it a day?

I've done my best to get a solid answer online but there seem to be varying opinions. I also called Denny's driveshaft but the rep said they had nothing that would work for my application.

Any input would be wonderful HAMB!

 

they made yokes with a weep hole, that require an O ring on the output shaft to seal. This type yoke has an unsplined part at the end, to fit over the O ring. As long as you don't get this type of yoke, you should be ok to do what you planned.

 

You're most likely going to have to replace the out shaft and the slip yoke that'll work with that output shaft. It also does't help that there were several different output shafts and slip yokes. You could always keep the drum parking brake and adapt whatever you'd need to do that. I had an old cast iron 4 speed Hydro that had an attached parking brake, and there was NO way it was going to work trying to adapt a slip yoke; I even half thought about using the drum to make a trans-brake, but I had two other Hydro's to work with at the time. I am Butch/56sedandelivery.

 

So any yokes without a weep hole and are splined the whole way are acceptable?

The problem with keeping the old drum is that it takes alot of room under the cab. To keep the engine where we wanted it, we would need to make a new cab tunnel but we do not have the tools or skills to fabricate. Also, the old brake was worn and rusted.

 

The splines on your outpu t shaft are very shallow. The current setup has a fixed yoke held on by a bolt. the driveshaft used a slip yoke built in to it. Like Butch stated you would need to gut the trans and change the rear shaft and related parts.

 

You can counter bore a slip yoke to fit were a bolt on yoke was.

 

Ah, I really don't wanna tear down the trans just yet to swap out the output :/.

The fixed output shaft I have isn't in bad condition. Only the drum rusted out. Would it be easier to reuse it? The universal is massive but the driveshaft will already be custom. There will also be a 4 inch extension where the brake used to sit.

Money is a big factor on the truck and at this time with COVID shutting jobs down.

 

Why not just remove the offending drum brake parts? with a torch and a grinder its doable?

 

I think he wants a slip yoke at the transmission....

 

I want a slip yoke transmission. I also want to use this beefy transmission. If I can't have both, I'll use the transmission.

So, remove the brake hardware and keep the bolted yoke?

 

I understand what he wants. Just my opinion the only way it would be reliable and not leak or vibrate would be to gut it and install the preferred output and slip yoke. nothing wrong with a drive line slip yoke. All of the OT 3/4 ton trucks I own have slip yokes in the driveshafts. Never caused any trouble. And you can change the U joint without trans fluid leaking out.

 

Yes its just that simple.

 

You might find a flange like the one I pictured and save a lot of work?

 

I've never had any trouble with the yokes being in the driveline either. If I remember correctly the truck originally had a split drive shaft with a carrier bearing.

By flange do mean a shorter yoke? Or are you suggestions a flange for the drive shaft that will accept the larger universal?

 

I think that there is a yoke sold aftermarket to convert bolt on yoke to be slip yoke.
However for millions of miles vehicles, mostly trucks, have had the slip yoke in the driveshaft. Since you need to make custom driveshaft anyway, why not duplicate what GM has done for decades. Ho to junkyard and get a truck driveshaft and it's carrier bearing. shorten as needed.

Sent from dumb operator on a smart phone

 

You and Old Wolf both have strong points. It's ultimately easiest to work with the bolt-on yoke get a driveshaft with the slip.

My last question is will any th400 bolt-on yoke work for this RV HD extension housing? I've seen that the roller bearing is not correct for standard yokes but standard yoke was not defined as either slip or bolt on. I'd prefer to not use the original from the e-brake as it extends out quite a bit. Also, the u-joint is mad massive.

 

Something like this 32 spline unit?

 

The problem you run into is how much the driveshaft will slide in and out, the 475 output has a flange very near the end of the splines and the slip yoke will hit that raised flange ( but it will work ) you can take and grind the flange down or find another output shaft. That trans with the parking brake probably does not have park in it so you will have to get the parts ( pall , rod , etc ) to get park operating. I am building one right now I will try and get a pic of the output shafts to show you the difference.

 

The shaft with the groves is for a bolt on yoke, a slip on yoke stops just past the splines, the other one is the standard output. The yoke slides on until where the shaft steps up so you gain about an inch of travel. Like I said you can just grind the other shaft down if you do not have another output shaft to use.

 

I have a 475 in my coupe from an 80's RV.
Mine had the brake, and park.
Took the brake off, replaced the tailshaft housing, aftermarket from summit.
Also new slip yoke from summit. It's over 900 hp so I have 1350 u-joints.
Took a little research to find the parts, but I have had no issues with it and summit had them in-stock.

 

Yes! If its easier to run I wouldn't mind using it.

Awesome pictures for reference! I do have park in this transmission.

Badvolvo do you recall which parts you used? Granted my engine is only 350 hp on a glorious day so I can search for my application.

 

https://fortwayneclutch.com/product...on-slip-yoke-w-counterbore-sku-t3-3-2431cbhp/
Something like this?

 

I will look into it. I just need to do a little searching on my summit account. However, I buy a lot so it may take a bit. I'll try to get back to you today.

 

Well that was easy. These may not be exactly what you are looking for, but works for me. My car is primary a drag car, limited street use. I would call ATI, they have been real helpful and make great American made products.

ATI housing - ATI401935 -note: this is a roller bearing unit. I expect you can get the bushing unit. They make a bushing unit as well. https://www.summitracing.com/parts/ati-401935
Strange yoke - STR-1650 - note: this is for the 1350 u-joint, I expect you can get one for a 1310. https://www.summitracing.com/parts/str-u1650

Hope that helps you out.

 

You're the man! I'll continue looking into these options and see what pops wants to do. This is our money truck after all

In the meantime, I'll get the engine and transmission cross members installed with what I have and swap out the extension housing at a later date. It's only a little hot in Vegas right now.

 

They make a slip yoke for an O-ring shaft but the problem is that you don't have much spline engagement with the end of the yoke being spline less and it being shorter than a regular slip yoke.
The aftermarket yoke on right vs stock yoke on left.

 

Oh wow thats a big difference. I see what ya'll mean that theres alot less throw on the yoke.

For the time being, Does anyone know if the e brake extension housing has the same mounting distance as a standard short extension housing?
It seems that which ever way I go the extension housing only changes from e brake to non ebrake. This is so I can get my transmssion crossmember drilled in and engine mounts welded in. I tried to get one from pick a part but not one th 400 transmssion

 

Something else to take note of is that the rear extension housing can be found to to either a small yoke or a large yoke. The large one is what you want. It is the same size as your bolt in yoke. The small one is the size of a 350. It would surprise me if you find any of this stuff in a junkyard any more. I know around me here in NC it is non existent.

 

I'm in the camp that says use a driveshaft slip joint. I assume you're going to need to build or have a drive shaft made, so why not just use a driveshaft slip joint when the new shaft is built? Lots of old Mopars have had their ball and trunion joint replaced with a driveshaft made with a slip joint. You can get them rated for pretty much any torque. Look under any rock crawler, heavier truck, or semi tractor and you'll see them in use.

 

If I keep the existing bolt in extension housing I'll be sure to use the larger yoke.

Ebbsspeed, we will have a driveshaft made to fit the truck. We originally wanted to use a slip joint to keep the driveshaft one piece to go without using a carrier bearing.
I have always assumed that split driveshafts have carrier bearings; please correct me if I'm wrong!

Also, I wanted to get a more in-depth forum with opinions on how to convert the TH475 into a regular TH400.

I'd like to still go with a slip yoke but its increasingly looking like I would have a better time buying a large OD yoke that's shorter than my current one and bolt that in with a split drive shaft.