727 Tail Swap

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jgchemie

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Trying to figure out if it's possible to swap the tail on between two 727 transmissions (sorry for the similar thread but it got jumbled up with my engine questions!)

Goal: Put a 400 BB into a 1969 A108.
Required: Transmission that mates to the 400 but has the tail with the top hanging mount and shorter length to fit the drive shaft.

Part that I have:
400 BB and matching 727 transmission from a 1976 B-series van
727 transmission from 1969 A108 van (and stock 318 LA engine)

I read that around 1976 the tails could not be interchanged with earlier 727 transmissions. However, this site doesn't mention any incompatibilities between the '69 and '76.

Anyone done this swap? How much work is it and can/should I rebuild the transmission and install a transgo shift kit at the same time?

PXL_20201125_203052315.jpg


PXL_20201125_203030482.jpg
 
I always keep the front planetary gearset with the output shaft it originated on. There are two different sets of splines; and they are very close; sometimes easy to mix up...they'll shear. The 76 is a much better trans; with part throttle kickdown, and wide direct drum bushing.
 
It will work fine, just keep your 69 gears and output shaft together. Many improvements in 1976 over the 1969 trans. I wonder why they changed that angle, I’ve never seen one fail there.
 
Sorry, I'm a bit confused- so take the front part of the 76, gears and all and attach only the tail housing? Will the output shaft from the 76 fit into the tail of the 69?

What about adding a level 2 transgo shift kit?
 
NO. Use the gears from the short one. To simplify, when you take the trans apart,and get back to the clip on the front of the output shaft, use everything from there back from the short one into the 76. Re-use the pump and front drums from the 76; everything in front of the clip. Plus of course, use the 76 valve body and kickdown arm. Forget about a shift kit for now.
 
NO. Use the gears from the short one. To simplify, when you take the trans apart,and get back to the clip on the front of the output shaft, use everything from there back from the short one into the 76. Re-use the pump and front drums from the 76; everything in front of the clip. Plus of course, use the 76 valve body and kickdown arm. Forget about a shift kit for now.
I think I got it! I'm assuming I'll need a rebuild kit for the '76.
Are there any gaskets/kits for the tail that I need to find for the '69? In other worlds, do you think I'll end up needing to buy two rebuild kits? One for the '76 transmission and a second for the '69 output shaft and tail housing?

Also, I'll hold off on the shift kit.
 
Just buy a seal up kit off ebay for $25.45 free shipping, but you'll need a special rear seal and a better pan gasket like $6.05 for red fiber; no cork, neoprene or rubber; either black or red fiber only. You'll have good internal seals and probably a good filter in there too.
 
Just buy a seal up kit off ebay for $25.45 free shipping, but you'll need a special rear seal and a better pan gasket like $6.05 for red fiber; no cork, neoprene or rubber; either black or red fiber only. You'll have good internal seals and probably a good filter in there too.
That sounds a lot better than the $1250 a transmission shop quoted me for doing the work. For someone that's never worked on a transmission but has done other suspension and engine work, how complicated is this job?
 
It's extremely complicated. But there are over a hundred old fools on here with more time than money and any one of them can advise you properly every step of the way.
 
It's extremely complicated. But there are over a hundred old fools on here with more time than money and any one of them can advise you properly every step of the way.

Thanks.... I think! I'll read through the FSM and decide if I'm up for the challenge. It's going to be a long winter.....
 
Don't put all your faith in a book or video. One little problem overlooked cuz it ain't in the book...and it has to come back out. Just be prepared to post tons of pics and tear into it. (Oh, and speak of the devil)...
 
Don't put all your faith in a book or video. One little problem overlooked cuz it ain't in the book...and it has to come back out. Just be prepared to post tons of pics and tear into it. (Oh, and speak of the devil)...

All of this still depends on whether I try to squeeze the 400 B into my A108 van or stick with the 318 (or buy a crate 360/408 magnum stroker....) But knowing the complexity of swapping out the transmission tail is key!
 
I think the 318 puts out more power than the 400. 400 needs some old 361 heads on it for a compression boost.
 
I think the 318 puts out more power than the 400. 400 needs some old 361 heads on it for a compression boost.
I was planning to add a stroker setup, new heads, manifold, etc. to either the 318 or the 400. The main challenges with the 400 are a) fitting it into the doghousing of the A108 and b) getting it to mate with the correct transmission. I've priced out the stroker/upgrades for both and they are about the same. Buying a 360/408 crate is a bit more expensive (and probably not as fun since I don't get to build it!)
 
Put a set of Edelbrock heads on that 400 to jack the compression and breathe like a ****. Who had a 383 Magnum Roadrunner back in the day? No 408 strokher gonna touch it.
 
Put a set of Edelbrock heads on that 400 to jack the compression and breathe like a ****. Who had a 383 Magnum Roadrunner back in the day? No 408 strokher gonna touch it.
Exactly why I'm still considering the 400 stroker (maybe to a 499) with Stealth or Edelbrock RPM heads! I might pop wheelies! But the fit....
The 318 can be stroked to 390 and basically drop right in. A crate 360/408 similarly can fit easily, just need to change the torque converter for externally balanced and slightly modify engine mounts but it cost the most.
 
All my cars are gonna outlive me..so i always go bb anymore for the extra resale value.
Interesting perspective :)
I rarely keep a car more than 3 years but it might take me three years to get this van running again!

I'm definitely more excited about the BB in the van but honestly worried that after I build it I'll have some major technical difficulties getting it installed.
 
It's easier to install that 400 than it is to rebuild an automatic.
This is why I might just take the two 727 transmissions to a local shop and pay $1,000. More fun to work on the engine IMO. But at least I know it's possible to do the tail swap now
 
As long as you never intend to go thru one, then I guess paying a shop would be okay...cuz if you ever do one, you'll be bangin ur head against a wall for ever paying somebody to do it for you:BangHead:...especially at that price! (Harder if it has issues after they're finished with it; very common).
 
They are one of the simplest automatics to go through. I did my first one in high school and it worked great. With the internet and all the resources available today someone with moderate mechanical skill, some tools, a large workbench, and some common sense, it shouldn’t be a problem.
 
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