[mathmagician]

ok, so I bought this thing with a mini-spool 4:10 rear end in it and I think I should probably swap it out before it all goes to hell. I'm thinking limited slip since it's mostly a street car and frankly the combo of the 4:10 and 4sp aod is questionable. rear ends and transmissions are a foreign language to me so can anyone point me in the right direction on how/where etc? I need to bulk up/research. books or links would be great.

 

[Cougrrcj]

With an AOD, you probably don't want to drop your rear gears to anything lower than 3.25s, at least if you want any performance out of it. With the 3.55s/AOD I have in my daily driver, the engine is turning a 'modest' 1850 at 60mph in OD. Right now with 4.10s you're turning around 3050rpm in D and 2050rpm in OD at 60mph.

As for the mini-spool, yes, by all means get rid of it and get a regular Traction Loc posi unit, or True-Trac (my choice), or even a Detroit Locker.

 

[cougarshaman]

limited slips use clutches
lockers use a mechanical device to engage both axles.

limited slips need clutches from time to time. lockers work until they break (almost never).

Search this forum for lots of discussion on the different types, since we tend to have a giant debate annually and a regular appearance of this issue about every 4 months or so.

 

[cougarshaman]

One of the best diff videos ever to explain it to you soundly.

 

[ahunt191]

Along with lockers and clutch based LSDs, there are also geared LSDs, like the Eaton Detroit Truetrac mentioned by Cougrrcj. Lockers are the strongest LSDs you can get and are found on most circle track race cars. Unfortunately, they can be a little rough on the street. They lock the wheels together like spools, until you turn. When turning, the locking mechanism clicks a lot. Although your turning radius will be better with a locker compared to your mini-spool, it will be much worse than it would be with a geared or clutch based LSD. I've heard the newer lockers are a little more bearable, but my money is going toward a Truetrac. Here's an exploded view and demonstration of the Truetrac.

As for your gear ratio, an AOD with 4.10 gives you a final drive ratio in overdrive of 2.70. That is great for highway economy and acceleration. I would stick with it.

 

[1969XR7Vert]

...limited slips need clutches from time to time...

Except True-Trac's which are helical gear driven (and do not even require firction modified lubes to be used).

 

[cougarshaman]

Yeah, there's an exception to the rule. I was just trying to give him some basics he could wrap his head around before getting too specific.

For that matter, there's a difference between older Detroit lockers and newer lockers built by the various companies. There are also air lockers, and lots of neato whizbang stuff. There's even the hono-drive 2 speed axles that $helby seemed to dig.

For a guy who don't know nothin', I figured that clutch/nonclutch was a good place to start describing the basics.

 

[1969XR7Vert]

Hate to point out yet another thing Andy, but "he" is a "she"!!

 

[mathmagician]

the nice thing about having a hit list of stuff to fix is I get to choose which one to do next ^_^
I like the idea of a geared lsd, I thought they were all clutched.

ok, so let me ask you this.
with the minispool (frankly not sure exactly what makes it "mini") on there currently, am I doing any damage to other parts of the car? and if so which ones, and how catastrophic is a potential failure.

 

[cougarshaman]

Increased loading of the driveline creates more stress on the universal joints around turns as the tires chatter in order to maintain speed relationship between axles. Pinion and carrier bearings get some unusual stress loads too, but nothing that a Ford unit can't handle.
I have a friend with a Pinto, replete with mini-spool in the 8 inch, and it's been in there for thousands of street miles. Eats u-joints, but the diff seems ok so far. If I were putting a new lsd in your car, I'd just go through the whole thing and install new bearings all over anyway. Axle bearings included.

Bob, Craigster had me so used to bending gender that I guess I was just on autopilot. Thanks for the correction. :0)
Got any tranny questions? >>

 

[ahunt191]

The mini spool is a small piece that locks the axles together and replaces the spider gears in an open carrier.
http://cgi.ebay.com/ebaymotors/8-Fo...ptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

You can convert back to an open differential by getting a new set of spider gears.
http://cgi.ebay.com/ebaymotors/FORD..._Accessories&hash=item19ac5905ba#ht_557wt_944

A (full) spool is a complete carrier
http://cgi.ebay.com/ebaymotors/9-Fo...ccessories&hash=item5644c99218#ht_2023wt_1169

 

[1969XR7Vert]

The mini spool is a small piece that locks the axles together and replaces the spider gears in an open carrier.
http://cgi.ebay.com/ebaymotors/8-Fo...ptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

You can convert back to an open differential by getting a new set of spider gears.
http://cgi.ebay.com/ebaymotors/FORD..._Accessories&hash=item19ac5905ba#ht_557wt_944

A (full) spool is a complete carrier
http://cgi.ebay.com/ebaymotors/9-Fo...ccessories&hash=item5644c99218#ht_2023wt_1169

Interesting, I never knew what that was about. Thanks.

 

[johnboy]

One of the best diff videos ever to explain it to you soundly.

Thanks Andy,

I finally understand how that works!!!

Jean

 

[Art]

I personally like a detroit locker or tru-trac. Someone usually chimes in about how rough and noisy the detroit lockers are, this is not what I've experienced (see sig).
Trac-Loc limited slip units have clutches and require additive to the lube, a large portion of the used ones you see at swap meets have cracked covers (common problem) . Aftermarket Trac-Loc's have steel covers and seem to hold up better than the OEM's.

 

[Royce Peterson]

I guess you've never drivin in or had a ride in a car equipped with a Detroit Locker made in the past 30 years. The current version street unts are utterly silent. You would never know it was there on pavement. On sand or gravel you will notice there is a lot of slipping of the inside wheel. They are bulletproof, need no special fluids, and will be the last differential you ever buy.

Along with lockers and clutch based LSDs, there are also geared LSDs, like the Eaton Detroit Truetrac mentioned by Cougrrcj. Lockers are the strongest LSDs you can get and are found on most circle track race cars. Unfortunately, they can be a little rough on the street. They lock the wheels together like spools, until you turn. When turning, the locking mechanism clicks a lot. Although your turning radius will be better with a locker compared to your mini-spool, it will be much worse than it would be with a geared or clutch based LSD. I've heard the newer lockers are a little more bearable, but my money is going toward a Truetrac. Here's an exploded view and demonstration of the Truetrac.

deleted video

As for your gear ratio, an AOD with 4.10 gives you a final drive ratio in overdrive of 2.70. That is great for highway economy and acceleration. I would stick with it.

 

[Art]

You can convert back to an open differential by getting a new set of spider gears.
http://cgi.ebay.com/ebaymotors/FORD..._Accessories&hash=item19ac5905ba#ht_557wt_944

Hahaha!
You're kidding, right?

 

[ahunt191]

Hahaha!
You're kidding, right?

No, a mini spool is removable. You're right, you would probably want to get a 2 spider gear kit like open differentials had in the first place. The 4 spider gear version probably wouldn't work. That was the only one I found as an example.

 

[ahunt191]

Royce and Art, I know this is the internet, but let's cut down on the snark, please. Geez, I feel like I am feeding the trolls.

For the purposes of full disclosure, apart from the last 6 months, I haven't driven a classic car or modified car in the past 10 years. If you want to know why, I'll tell you, but I don't think my bio is that interesting. From 1997 to 1999, I worked in a performance shop performing a lot of grunt work. It gave me a chance to drive and ride in a lot modified cars (no imports). The cars with lockers were not silky smooth or silent. They were as I described. If new lockers are better, great. In post #5, I admitted to my inexperience.

 

[Art]

The ebay link you provided shows parts that would be impossible to put in a 8" or 9" carrier.
And Royce is correct, the new SL prefix Detroit Lockers are as quiet as a clutch type. The old Detroit Lockers did make some noise that was somewhat noticeable at first but you quickly got used to it, and I've never noticed a decreased turning radius with any LSD.

Royce and Art, I know this is the internet, but let's cut down on the snark, please. Geez, I feel like I am feeding the trolls.

For the purposes of full disclosure, apart from the last 6 months, I haven't driven a classic car or modified car in the past 10 years. If you want to know why, I'll tell you, but I don't think my bio is that interesting. From 1997 to 1999, I worked in a performance shop performing a lot of grunt work. It gave me a chance to drive and ride in a lot modified cars (no imports). The cars with lockers were not silky smooth or silent. They were as I described. If new lockers are better, great. In post #5, I admitted to my inexperience.

If you want silky smooth and silent you should buy a Cadillac.

 

[Royce Peterson]

The Detroit Lockers used in Nascar and Trans Am racing are the "H" series. They make a wonderful sort of clack clack clack ratchet noise when going slowly around corners. It is music to my ears, I have one of these going in the turquoise GT-E. This type of Detroit Locker was optional equipment in some Ford products in the 1960's to 1971. The reputation from these older units and current racing type DLs confuses people who do not work on differentials.

Royce and Art, I know this is the internet, but let's cut down on the snark, please. Geez, I feel like I am feeding the trolls.

For the purposes of full disclosure, apart from the last 6 months, I haven't driven a classic car or modified car in the past 10 years. If you want to know why, I'll tell you, but I don't think my bio is that interesting. From 1997 to 1999, I worked in a performance shop performing a lot of grunt work. It gave me a chance to drive and ride in a lot modified cars (no imports). The cars with lockers were not silky smooth or silent. They were as I described. If new lockers are better, great. In post #5, I admitted to my inexperience.