Billet TH400 Adapters

djsy934

Member
There seems to be an interest in making some of these, I will start this interest thread and see what we can do. There will need to be a price increase of $50 over the 4L80E ones do to the fact they are 1/2" thicker. This is to cover the extra material and machining cost. I have only ever made one of these for gt67sy. Here it is machined sitting next to a 4L80E one. The TH400 is on the right.

Price will be $445 + $25 for insured shipping in the US, Canada and elsewhere extra + PayPal fees unless sent as personal transfer.


1.fivetodrive Paid and shipped
2.henry283 Paid and shipped
3.CalgarySS Paid and shipped
4.Bryan2710 Paid and shipped
5.Sloweracing Paid and shipped



Bolted to a dummy TH400 case:





[/QUOTE]
 
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djsy934

Member
Re: Billet TH400 Adapters

Interested but why are they thicker?
I worked with gt67sy on the design of this, I can't remember why the extra thickness, I'll have to check with him on that. I'm sure it is because of the length of the output shaft.

Maybe the shaft can be cut down, or a different shaft?? If we can get the thickness down we can get the cost down also.
 

djsy934

Member
Re: Billet TH400 Adapters

I found some pics he sent me through email, yes the shaft is too long, even with the extra thickness he was going to have to cut the shaft down 3/8" and maybe up to 7/16". The material starts at 3 1/2" and there is a 1/8" locating diameter going into the tranny.

Here is a pic with the transfer case slid all the way onto the output shaft.



And here is the distance between the trannny and transfer case.

 

djsy934

Member
Re: Billet TH400 Adapters

Will this allow the use of stock driveshafts ?
I don't think so, we would have to have the overall length of the TH400 with the adapter to be the same as the 700R4 with the adapter.

Adjusting the thickness of the adapter is no big deal, we would need to get an output shaft to accommodate.

If we could do this, we could possibly even use the stock cross member?

If someone is willing to work with me on this, maybe we can make it work?

I found this dimension chart online. So it looks like it is close.

 

henry283

Member
Re: Billet TH400 Adapters

You can add me to the list. I can help with the design updates.

I don't think so, we would have to have the overall length of the TH400 with the adapter to be the same as the 700R4 with the adapter.

Adjusting the thickness of the adapter is no big deal, we would need to get an output shaft to accommodate.

If we could do this, we could possibly even use the stock cross member?

If someone is willing to work with me on this, maybe we can make it work?

I found this dimension chart online. So it looks like it is close.

 

henry283

Member
Re: Billet TH400 Adapters

Quick research shows 1 1/2, 2 1/2 and 5 inch output shafts available. transmission flange to end of shaft.
 

CalgarySS

1000 miles and counting..
Re: Billet TH400 Adapters

Thanks for starting the ball rolling on this. Mine is not far enough along to help with R and D, but I am interested.
Gord.
 

gt67sy

Member
Re: Billet TH400 Adapters

We cut 3/8 off the end of the th400 short shaft and have full engagement on the th400 splines in the 32 spline input shaft on the transfer case.

No you will not be able to use the stock drive shaft or propshaft. Drive shaft will have to be shortened and the propshaft lengthened. Drive shaft length is going to be pretty close to that or a 4l80e drive shaft but we will have final numbers coming soon. Going in the truck within the next two weeks. We are working out some shifter things to ensure the stock shifter works as I don't want and after market one.

My th400 is a reverse manual valve body with a trans brake. Let me know if there is anything I can help you guys with. John has been so helpful during this whole process we have traded some many emails and texts. Right know I just got a hold of a jsm 4l80e cross member that I'm hoping will be pretty close also. Like a said just sorting out some shifter issues and waiting on summit racing to deliver arp flexplate bolts and torque converter bolts
 

Bryan2710

New member
Re: Billet TH400 Adapters

Is there a difference between a the 400 trans for 4wd or 2wd . If so which one is needed ? You can sign me up for one if we get a list of what's all needed . Thanks
 

henry283

Member
Re: Billet TH400 Adapters

Two wheel and 4wd cases are slightly different. But they can be interchanged. The issue is what length output shaft we use. Early 4x4 cases used 4 1/2 inch length later 85 up used 2 1/2 inch length. So if we go with this solution we need to settle on what output shaft length to use. I suspect the 2 1/2 inch version would give us the closest match to the stock length. I'm not worried about it being a bolt in solution what ever length works with the transfer case is fine. I'll fab everything else or have it custom made.

Is there a difference between a the 400 trans for 4wd or 2wd . If so which one is needed ? You can sign me up for one if we get a list of what's all needed . Thanks
 

djsy934

Member
Re: Billet TH400 Adapters

Starting to look at this a little closer, a 32 spline input shaft is still needed. A quick search shows these are the available output shafts for the TH400:

http://offroaddesign.com/TH400Tech.htm

The 4x4 version looks like the shortest one.

The 32 spline input shafts that are available on this forum are 3/4" longer than they need to be at the spline end. This is because the first 4L80E's that were put in required a "spacer adapter" which are 3/4" thick, so they increased the spline length to compensate for this.

Now that we make the billet adapter, that extra 3/4" is no longer necessary.

We may need to cut this extra length down if we are going to try and use the stock crossmember and prop shafts. The TH400 is already 1" longer than the 700R4 to begin with.

The more I think about it, I don't think it is going to be possible to use the stock crossmember and prop shafts. The TH400 being 1" longer means we need to make the Original SyTy tail housing 1" shorter to keep the distance the same as stock and this won't work.
 
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henry283

Member
Re: Billet TH400 Adapters

I got my transfer case input shafts from the group buy. Im ok with the adapter being designed to fit that input shaft.


Starting to look at this a little closer, a 32 spline input shaft is still needed. A quick search shows these are the available output shafts for the TH400:

http://offroaddesign.com/TH400Tech.htm

The 4x4 version looks like the shortest one.

The 32 spline input shafts that are available on this forum are 3/4" longer than they need to be at the spline end. This is because the first 4L80E's that were put in required a "spacer adapter" which are 3/4" thick, so they increased the spline length to compensate for this.

Now that we make the billet adapter, that extra 3/4" is no longer necessary.

We may need to cut this extra length down if we are going to try and use the stock crossmember and prop shafts. The TH400 is already 1" longer than the 700R4 to begin with.

The more I think about it, I don't think it is going to be possible to use the stock crossmember and prop shafts. The TH400 being 1" longer means we need to make the Original SyTy tail housing 1" shorter to keep the distance the same as stock and this won't work.
 

Sloweracing

New member
Re: Billet TH400 Adapters

I also got in on the group buy for the 32 spline input shaft so what ever works is good for me. I am cool with shortening the drive shaft and getting a new prop shaft made.
 

djsy934

Member
Re: Billet TH400 Adapters

I got what we think is a medium length 4x4 output shaft, dimensional it matches up pretty close but it looks like it has a spot for a speedo gear. :dunno: Maybe someone can verify this. see pic:



Slid it into an empty TH400 case and it sticks out 2 1/4". The chart says it should stick out 2 1/2".



I took my transfer case with a Mark Williams shaft installed and assembled them together the best I can and the distance between the 2 fully bottomed out is 1 3/8". So I figure the distance between the 2 mating surfaces should be 1 3/4". This allows for the 1/4" discrepancy from what they say it should stick out to what I got plus an 1/8" so it doesn't bottom out if it does stick out the 2 1/2" they say.



With this I think I am ready to make an adapter.
 

djsy934

Member
Re: Billet TH400 Adapters

We are dangerously close to being able to use the stock cross member and prop shafts. The original tail shaft adapter for our SyTy's are 2 3/8" from transmission mounting surface to transfer case mounting surface. We are now at 1 3/4" with our new adapter design, and we are giving the extra 1/4" for the discrepancy of what they say it should stick out to what I got plus an extra 1/8". If it is in fact that the TH400 is 1" longer than the 700R4, then we are only about 5/8" off.

It will require shortening the medium length 4x4 output shaft by about 1/2"- 5/8 ".

Is this a goal we want to achieve?
 

henry283

Member
Re: Billet TH400 Adapters

I ordered the short 4x4 output shaft from advanced adapters. When i get it ill take pics and dimensions. I can send it go you if that helps.

Keeping it close to stock will make it simpler for non fabricators to do the swap. If it is that close maybe a simple plate adapter can be machined to fit. I can proto that.

We are dangerously close to being able to use the stock cross member and prop shafts. The original tail shaft adapter for our SyTy's are 2 3/8" from transmission mounting surface to transfer case mounting surface. We are now at 1 3/4" with our new adapter design, and we are giving the extra 1/4" for the discrepancy of what they say it should stick out to what I got plus an extra 1/8". If it is in fact that the TH400 is 1" longer than the 700R4, then we are only about 5/8" off.

It will require shortening the medium length 4x4 output shaft by about 1/2"- 5/8 ".

Is this a goal we want to achieve?
 

djsy934

Member
Re: Billet TH400 Adapters

I'm a little concerned that the short output shaft will be too short. With the mid length shaft we have a 1 3/8" space between the transmission and t-case with full spline engagement. The short shaft is 1 1/4" shorter than the mid length shaft. It looks like with the short shaft there will be only a 1/4" gap between the transmission and t-case with full spline engagement. The original SyTy tail housing is 2 3/8" thick, so if the TH400 is 1" longer than the 700R4, then our new adapter should be 1 3/8" thick. I will get a 700R4 transmission case on Monday and check the dimensions.


I ordered the short 4x4 output shaft from advanced adapters. When i get it ill take pics and dimensions. I can send it go you if that helps.

Keeping it close to stock will make it simpler for non fabricators to do the swap. If it is that close maybe a simple plate adapter can be machined to fit. I can proto that.
 
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