Transmission / Overdrive: Avanti T56 Rear Mount and Shifter Position

[sweetolbob]

My initial thoughts on fabing a rear mount were as simple as just narrowing the old 4-speed mount and bolting it in place. When I looked at the initial amount of work required to do that and the amount of cutting necessary, I opted for a totally new mount.

This design uses two of the original mounting holes in the frame and requires two more be drilled. The "rubber" mount this was designed for is Prothane 7-1604-BL

This is the mount I ended up with, Top View

[IMG][/IMG]

It is a combination of 1 1/2" X 3" rectangular box and a 3/16" X 1 1/4" hot rolled.

Bottom view

[IMG][/IMG]

Because I wasn't sure about the flex of the rectangular tubing, I added a couple of stiffeners between the top and bottom


[IMG][/IMG]


This is a simplified drawing of the mount


[IMG][/IMG]


And the mounts used


[IMG][/IMG]

From the "better lucky than good camp" is the shifter location. I fits like it was designed to be installed there. Top Shot of T56

[IMG][/IMG]

The reverse lockout solenoid "not Shown" will be a tight fit and may require a slight mod on the console side. It fits on the drivers side of the shifter housing. Because there is already an access hole cut in the tunnel, I'll probably just enlarge it allow the installation of the lockout solenoid and build a plate to cover it all.


Shifter installed


[IMG][/IMG]

The current installation sets the T56 just clear of the top of the tunnel. When the suspension in reinstalled and I get the Avanti to final ride height, I may need to massage something but the current install sets close to the original four speed location height so we shall see.

Now onto the front suspension installation and then "PAINT" WAHOO!!!! The light at the end of the tunnel may now not be a train.
Bob

[WCP]

Looks good Bob. Being "vertically challenged", I straightened the shaft to bring it up vertically from the mount, but that position is probably good for you. However, the boot enclosure may be problematic. I fab'd a plate with a leather shifter sock attached to seal that location beneath the console cover piece.

[johnod]

What engine are you using Bob?
Are you hooking up the reverse lockout?
There was a guy making custom springs if you're chooseing not to.
I have one and it works well

Below is also a nice piece.

http://www.tickperformance.com/tickshift-173-skip-shift-delete-plug/

Is this an LT1 trans?
Are you using the stock pull clutch, bell etc?

i got rid of all the electrics stuff except the speedo.

You'll like the trans, but you need a stiff gear to use 6th.

[sweetolbob]

What engine are you using Bob?
Are you hooking up the reverse lockout?
There was a guy making custom springs if you're chooseing not to.
I have one and it works well

Below is also a nice piece.

http://www.tickperformance.com/tickshift-173-skip-shift-delete-plug/

Is this an LT1 trans?
Are you using the stock pull clutch, bell etc?

i got rid of all the electrics stuff except the speedo.

You'll like the trans, but you need a stiff gear to use 6th.

John

The engine is a 383 SBC based on a 70's era two-piece main seal block

I do plan to use the reverse lockout to avoid any "surprises" by hitting reverse at speed. I need to wire the speedo and backup lite switch so it's not much effort to wire the lockout.

Appreciate the skip shift eliminator but I'll just leave the solenoid, it's not taking up much room. I see no reason to hook it up as I don't need to meet EPA fuel standards


The trans is an LT-1 and I'm using the OEM hydraulic setup by fabing a mounting bracket and modifying the Avanti clutch pedal. The flywheel is centerforce with a stock style aftermarket clutch setup.


The gearing is 3:55 as that was the lowest I had on hand when I rebuilt the rear end. After it's on the road, I'll decide what is appropriate for my driving style.

Bob

[sweetolbob]

Looks good Bob. Being "vertically challenged", I straightened the shaft to bring it up vertically from the mount, but that position is probably good for you. However, the boot enclosure may be problematic. I fab'd a plate with a leather shifter sock attached to seal that location beneath the console cover piece.

Bill

Thanks again, As you know, I'm tall enough that I'll probably have a shifter like yours as the seat will be all the way back and my arms are relatively long. Straight up and short. The one on the shifter was a throw-in from the guy I purchased it from and make it easy to handle the shifter setup. I'm going to keep your shot for reference when I start to finish the console area

For future reference I measured for the necessary drive shaft length and it is 50" as opposed to the original 52.5" shaft for the original 4-speed. My math suggests that the T56 is 2.5" longer that the T10.


Bob

[johnod]

John

The engine is a 383 SBC based on a 70's era two-piece main seal block

I do plan to use the reverse lockout to avoid any "surprises" by hitting reverse at speed. I need to wire the speedo and backup lite switch so it's not much effort to wire the lockout.

Appreciate the skip shift eliminator but I'll just leave the solenoid, it's not taking up much room. I see no reason to hook it up as I don't need to meet EPA fuel standards


The trans is an LT-1 and I'm using the OEM hydraulic setup by fabing a mounting bracket and modifying the Avanti clutch pedal. The flywheel is centerforce with a stock style aftermarket clutch setup.


The gearing is 3:55 as that was the lowest I had on hand when I rebuilt the rear end. After it's on the road, I'll decide what is appropriate for my driving style.

Bob

I think you might find 3:55 doesn't do the trick for you.

I'll be watching this thread , sounds like a good one.

[WCP]

Bob, Although we are comparing apples and oranges, GM setup with T56 to Stude with T5 (no adapter), these were my measurements. The Ford T5 is 24" overall length, excluding output shaft. The T10 is 21 5/8", so the T5 is 2 3/8" longer. Taking the 2 3/8" off the T10 driveshaft (51 29/32 - 2/38 = 49 17/32"). I had a driveshaft cut to 49.5" but the shop did a poor job and had to be discarded later. I then acquired a NOS shaft (1561875) from Sasco with a length of 49 23/32" or 7/32" longer than the desired 49.5. This shaft works well but, I judge, is at the limit, and could be reduced, as I recall, 1/2 - 1". I would have to measure the yoke free travel on the level as I didn't note that measurement. I'm using a Ford slip joint with 1330 cross cups and a Napa 1330/1310 cross. The Ford slip joint is 1/4" longer from cross centre to slip surface "bottom". If you would like the free travel measurement, I can do as the car, at the moment, is up on skates (winter storage). Bill

[sweetolbob]

Bob, Although we are comparing apples and oranges, GM setup with T56 to Stude with T5 (no adapter), these were my measurements. The Ford T5 is 24" overall length, excluding output shaft. The T10 is 21 5/8", so the T5 is 2 3/8" longer. Taking the 2 3/8" off the T10 driveshaft (51 29/32 - 2/38 = 49 17/32"). I had a driveshaft cut to 49.5" but the shop did a poor job and had to be discarded later. I then acquired a NOS shaft (1561875) from Sasco with a length of 49 23/32" or 7/32" longer than the desired 49.5. This shaft works well but, I judge, is at the limit, and could be reduced, as I recall, 1/2 - 1". I would have to measure the yoke free travel on the level as I didn't note that measurement. I'm using a Ford slip joint with 1330 cross cups and a Napa 1330/1310 cross. The Ford slip joint is 1/4" longer from cross centre to slip surface "bottom". If you would like the free travel measurement, I can do as the car, at the moment, is up on skates (winter storage). Bill

Bill

You continue to add a great deal of knowledge to the forum. I'm going to continue to add to this for future reference.

I've have a pix of the T56 vs T5 from the net.



I measured the 50" center to center length with the Avanti II four speed yoke inserted with about 5/8" free travel on the output shaft. It's nice that a lot of yokes interchange as I hope to find one at the local swap meet next week as mine has some scoring in the sealing area. For my setup, 49.5" (approx.) would leave too little yoke on the output shaft. That's to bad for me as a lot of early Camaro's used that length but I plan to do Wrecking Yard search later this week to see if I can find the length I need. Otherwise, it's off to Joint Clutch and Gear to have mine shortened.

Whether it's apples, oranges or some combination my objective is to leave a search-able set of posts on the forum to help members in the future with T56 conversions. Your additions greatly add to that base from a Studebaker and T5 comparision standpoint.

Bob

[johnod]

Here's some info. dimensions etc

http://www.5speedtransmissions.com/6_speed.html

And a calculator too.

http://www.5speedtransmissions.com/gear_calculator.html

[WCP]

Bob, as my car sits, I have 1" from seal face to slip joint face. Based on the polish area on the joint caused by the dust boot, it would appear that I have 5/8" free play, seal to radius, with the car loaded with a full trunk (trip to last years S.B. meet). I would prefer a bit more and could add 1/2-1" by shortening the driveshaft that amount, as the slip yoke I'm using has a slip surface length of 4 7/8". The Stude length is 4 3/16". There must be longer GM yokes than the one you have.
There is some evidence that the dust boot has occasionally been into the yoke radius. Radius is 1/8". Happy to add what info I've got. Bill

[grobb284]

Sweetolbob, some nice work on your install.

[johnod]

FYI

There is a lot of talk on various forums re what's the best tans fluid, synthetics , royal purple etc etc
My trans guy said to use the GM atf, i did, works fine for me.

[sweetolbob]

Bill

I've usually left about 3/4" exposed and after your post and further review, I'll leave a heavy 3/4" so I'll need about 49 3/4" C/C on the shaft. My yoke is the slightly longer 5.5" 27 spline. Further investigation shows there is an 8" option, if necessary. This setup should allow about 3 inches of yoke/shaft engagement so I'll go with that initially.

John

After many questions locally and net searches, I have setting in a box four-quarts of Pennzoil Syncromesh fluid which by most reports is the source of the GM Syncromesh Fluid you described. Thx, The GM fluid seems to be the one that there is little negative about it's use. That actually makes some sense.

Gene

Thanks for the thoughts, I still need to see a few newer shots of your Avanti, which should impress the forum folks if they have not been exposed to it already.

Bob