Anyone here running an SM420 with AA 3-speed t-case adaptor? Can you use the toyota 4-speed driveshaft on the front, or do you still need to use a 3-speed upper on the front output, as required with plate adaptors?

I recently picked up a complete SM420 with the AA adaptor, and have been saving up for a t-case and driveshafts. HOWEVER, I'd like to go ahead and have the driveshafts made up since Jesse's got a special going on (thanks for the heads up Shane). I just don't have the upper 3-speed half if that's what's needed.

Thanks,

Bill C.

This kind of depends on your current setup. If you are going to get custom shafts, maybe Jess will have the flange that you need. I had to use an early 3 speed flange at the t-case for my drive shaft, but I am using a plate adapter. I would imagine that you would need to match the flange pattern on your t-case front output.

Depending on how you install the AA kit you can run stock 4 speed driveshafts front and rear (from 1974 to 83).
Change the front flange of your 3 speed case to a flange that comes on 4 speed t-cases (or a 4 speed pinion flange will work also)
Beware some 4 speed t-cases have fine spline front flanges which will not work with your 3 speed case.
The AA design fits both styles of flanges unlike the plate adapters.

** check your AA parts for cracks**
I have a used spud shaft from AA that has stress cracks and it's even starting to twist a little.

steven@extremebends.com

Steven,

Thanks - I figured the length of the AA adaptor allowed for the 4-speed flange.

I've got a 69 3-speed case and my original 76 4-speed case that I was hoping to rebuild/combine, but my wife's computer dumped the e-mail directions I'd gotten on how to do it. Been looking for an affordable 74ish 3-speed case in good condition as an alternative- would the 76 4-speed flange fit on that particular 3-speed case?

The spud shaft appears to be in great condition.

I've already flipped my springs on the rear to get about 4.5 inches to accomodate the SM420 and AA (5.5") plate, so hopefully I can get the driveshafts to fit my current configuration as well as the SM420.

Bill C.

Are you running a V8 or stock 6??
depending on how much lift you have and where you locate your axle on the rear springs you might be able to squeeze a stock length front shaft in the rear (good for trail fixes)
I've seen it done on a V8 set-up

I have a good selection of driveshafts and t-cases (even the 1974 one) if you can't find anything local let me know, I'm located in the lower mainland of British Columbia so the freight might be $$.

Your 76 case will work if you re-shim your 3 speed guts into it, plus you'll have to change the bearing in the back of the case (the one under that cone shape cover)) because your spud shaft will have the dimensions of the 3 speed tranny output shaft.

The nose cone off your 1976 will fit the early case,
I would use the complete nose cone off your 1976, this makes for an easy swap.
Toss out your top cover off 3 speed while you're at it
Use the top cover off the 4 speed (the cover has the vent and the pivot for the low/hi range linkage)
The 4 speed linkage is easier to convert to the SM420 plus less likely to bind.
Look at the linkage on your 4 speed and you'll see it's just a better design then the 1969 set up.

If I've missed something let me know,

steven@extremebends.com

Steven,

I may contact you in the future on a t-case if I can't figure out how to do the swap. Things have been on hold due to Christmas, but I hope to pull everything apart in late January.

I'm running the stock 6 so the front driveshaft is a few inches too long even after the spring flip.

On the t-case, since the rear bearing for the AA spudshaft needs to be from a 3-speed case, would I just order a 3-speed rebuild kit and use in the 4-speed case? Any differences in the idler shaft between the 2? Can I just use the metal spacer from the 3-speed case, or will I need even more shims? I've never taken a case apart fully, so this is new territory for me. Almost wondering if it would'nt be easier to see if AA would sell the 16 spline spud shaft and just rebuild my 4-speed case?

I already got a t-case shifter setup modified for the SM420.

Sorry for all the questions.

Bill C.

For the amount of gear ratio difference you get I would use a 4 speed case, much quieter, easier to find, stronger, and cheaper if you already have the 4 speed case.
I've run both, there is a bit of gearing loss but you're using a SM420 which has approx doubled your crawl ratio.

The idler shafts are the same. I don't have the shim part# handy.
T-cases are pretty easy, the idler gear shims have grooves you have to line up to install, there are a few pins in the case, a few ball bearings, nothing too tough.

steven@extremebends.com

I'm not sure how you do it, but a few of the other members of so. cal. tlca have put the guts of the 3 speed case into a 4 speed case to get the best of both worlds. Check with a guy that goes by the name pin head here on the board. Also does your adapter have the mounts under it for the chevy turbo 350 tranny mount? If it does I would fab up a cross member under there and not on the back of the t-case as it helps reduce your chances of creaks and leaks.

Just my :beer: worth.

Mike,

I've already picked up an AA cross member for the t-case. I'll post the 3-speed gears question in January when I go to do the swap - unless someone reads this and wants to post now.

Thanks.

Bill C.

Originally posted by MVANDYKE
I'm not sure how you do it, but a few of the other members of so. cal. tlca have put the guts of the 3 speed case into a 4 speed case to get the best of both worlds. Check with a guy that goes by the name pin head here on the board.
Just my :beer: worth.

It wasn't me. The guy in SoCal TLC that did the 3 sp gears in the 4 sp case is Ed G.

O.K. So I got the wrong guy. But your still guilty :D

Michael,

Did you ever remember who had the details on the 3-speed gears to 4-speed case rebuild???

Still trying to nail down my options. Ponied up for Jess's $200 long travel special on the front driveshaft. Only thing left is the t-case...

Option 1: Purchase a good 74 t-case.

Option 2: Purchase AA 16 spline spud shaft ($239) and use my 4-speed case.

Option 3: Rebuild the 76 case with the 69 gears?

Need to have all parts in hand by Jan. 26 :D

I'm not sure how you do it but I'll send an e-mail to the guy who did it and get back to you. :beer:

Thanks :D