• Welcome to the new SAOCA website. Already a member? Simply click Log In/Sign Up up and to the right and use your same username and password from the old site. If you've forgotten your password, please send an email to membership@sunbeamalpine.org for assistance.

    If you're new here, click Log In/Sign Up and enter your information. We'll approve your account as quickly as possible, typically in about 24 hours. If it takes longer, you were probably caught in our spam/scam filter.

    Enjoy.

Shifting A4LD

B

Bill Blue

Platinum Level Sponsor
What is the best strategy for shifting the A4LD into 4th (OD) and converter lockup? Is the ability to lockup in 3rd (1:1 ratio) important in a car with lots of horsepower? I'm thinking of combining switches so that the trans would lock up only as it was shifted into 4th. 3rd (1:1 would only be available with an unlocked converter. Or to put it another way, OD (1:.75) would only be available with a locked up converter. Bad idea?

Bill
 
Barry

Barry

Diamond Level Sponsor
Bill Blue said:
What is the best strategy for shifting the A4LD into 4th (OD) and converter lockup? Is the ability to lockup in 3rd (1:1 ratio) important in a car with lots of horsepower? I'm thinking of combining switches so that the trans would lock up only as it was shifted into 4th. 3rd (1:1 would only be available with an unlocked converter. Or to put it another way, OD (1:.75) would only be available with a locked up converter. Bad idea?

Bill
Click to expand...


A typical automotive torque converter has something like 5% "slippage", so I doubt that you would notice much performance difference between 3rd gear locked or unlocked unless you were right on the RPM borderline of a pretty radical cam. IMO, the main benefits of a lockup clutch are a little less RPM and a little more fuel mileage at cruise.

I would go with lockup only available in 4th gear at "cruise" (aka, high vacuum) throttle, so the shift sequence would be 1st unlocked, 2nd unlocked, 3rd unlocked, 4th unlocked and then torque converter lockup. With 5% slippage, it would be numerically equal to 2.59:1, 1.54:1, 1.05:1, 0.79:1 and 0.75:1.
 
Last edited:
P

pembertonltd8

Donation Time
I have an A4LD tranny connected to my V6. I am trying to find out how I can connect the over drive so that it works. Right now, I am running about 2700 rpm at 60. Can anyone help me
 
Barry

Barry

Diamond Level Sponsor
pembertonltd8 said:
I have an A4LD tranny connected to my V6. I am trying to find out how I can connect the over drive so that it works. Right now, I am running about 2700 rpm at 60. Can anyone help me
Click to expand...


The search function in the new website software is a lot better than in the past. A search (top right of forum pages) for "A4LD" brings up a lot of potentially useful information.

Note that early and late A4LD transmissions are controlled somewhat differently; which version do you have?
 
husky drvr

husky drvr

Platinum Level Sponsor
pembertonltd8 said:
I have an A4LD tranny connected to my V6. I am trying to find out how I can connect the over drive so that it works. Right now, I am running about 2700 rpm at 60. Can anyone help me
Click to expand...

P,

Just for curiosity, are you sure your OD is not working?

How are you reading your RPM's? Are you sure your tach is reasonably accurate?

What rear end and its ratio is installed in your Alpine? What tires?

Reason I'm asking is a 23 inch diameter tire would give about 877 revs per mile. With an original rear end geared at 3.89:1 and 0.79
(OD w/o lockup ) would show almost exactly 2700.

Just a thought,
 
Barry

Barry

Diamond Level Sponsor
Start by entering A4LD in the forum search box at the top-right of this page and then reading the relevant threads. After that, a google (or equivalent) search for something like "early vs late A4LD transmission" should be helpful.

FWIW, I think over drive is working in your A4LD. With factory sized rear tires and without OD, 60 MPH would be about 3,600 RPM with a 3.89:1 rear axle and about 3,900 RPM with a 4.22:1 rear axle. With factory diameter rear tires and a 0.75:1 transmission ratio (overdrive 4th gear in an A4LD) 60 MPH calculates to about 2,705 RPM with a 3.89:1 rear axle ratio or about 2,934 RPM with a 4.22:1 rear axle ratio.


EDIT: Don and I did not see each other's posts, but great minds think alike (or something like that).
 
Last edited:
husky drvr

husky drvr

Platinum Level Sponsor
Might have more to do with this link:

The Knack

forum.sunbeamalpine.org forum.sunbeamalpine.org

Either that, or as my 9th grade English teacher used to finish that saying, "Great minds think in the same channels and small minds think in the same ditches.
 
P

pembertonltd8

Donation Time
husky drvr said:
P,

Just for curiosity, are you sure your OD is not working?

How are you reading your RPM's? Are you sure your tach is reasonably accurate?

What rear end and its ratio is installed in your Alpine? What tires?

Reason I'm asking is a 23 inch diameter tire would give about 877 revs per mile. With an original rear end geared at 3.89:1 and 0.79
(OD w/o lockup ) would show almost exactly 2700.

Just a thought,
Click to expand...
I am running a stock alpine rear end. I will have to measure the trie and see what it is. Isn't there a switch or something that I should have that would put it into OD.
 
Barry

Barry

Diamond Level Sponsor
pembertonltd8 said:
I am running a stock alpine rear end. I will have to measure the trie and see what it is. Isn't there a switch or something that I should have that would put it into OD.
Click to expand...


Unless you are using unusually large diameter rear tires or your MPH / RPM information is wrong, it appears that your "stock alpine rear end" has a 3.89:1 gear set.

You don't have to measure the rear tires; the size markings on the sidewall are all that is needed.

The A4LD transmission is basically a C3 transmission with an extra (4th) 0.75:1 gear and a lock-up torque converter. All 4 gears were hydraulically shifted and torque converter lockup was activated by an EEC (electronic) controller. Later versions of the A4LD had a "4th gear inhibit solenoid" which prevented 4th gear (OD) from being engaged when the solenoid was activated by the EEC. The bottom line is that an A4LD will hydraulically shift into 4th gear (OD) unless it is prevented from doing so. Torque converter lock-up requires an electrical signal. Converter slippage in a light weight / low aerodynamic drag vehicle (i.e., a Series Alpine) at highway speed is probably less than 5%, so there may not be much benefit from converter lock-up.
 
Last edited:
Barry

Barry

Diamond Level Sponsor
pembertonltd8 said:
Thanks for the info. I guess that I must have OD in my car. It shifts into all 4 gears.
Click to expand...



If your A4LD transmission shifts into 4th gear, then you have "overdrive".

FWIW, a Tiger with factory diameter rear tires, a 1.00:1 4th gear ratio and a 2.88:1 rear axle ratio also turns about 2,700 RPM at 60 MPH.

A Tiger can handle more gear at Interstate highway speeds, but I think your transmission / rear axle combination is appropriate for a "mild" Ford 2.8 V6 engine.
 
Last edited:
You must log in or register to reply here.
Top