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Discussion Starter · #1 ·
hello
I am currently trying to make a decision on what type of differential to use . The currant one is a gm 12 bolt Posi unit and the clutches were acting up last fall. I am considering a Detroit locker. Since I have never used one of these I'm not sure what way to go. I have a 72 Vega with 373 gears and a mini tub. Tires are 30 inch x 15 wide. 700 r4 transmission. I don't race the car but its a great street car. Any advise?
 

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Discussion Starter · #5 ·
Before you throw out your 12bolt. Have you tried the limited slip additive. ? Makes a world of difference sometimes ! View attachment 622920
Before you throw out your 12bolt. Have you tried the limited slip additive. ? Makes a world of difference sometimes ! View attachment 622920
for sure i have replaced the oil and additive twice now. The clutches are just worn its been part of the car for at least 15 years not sure about the previous owner and i beat up on it. Just looking for more positive launch. and thought a locker would be the option ??
 

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Discussion Starter · #10 ·
if you are just launching the car, a real ratchet locker might be suitable. The Eaton 187C197A.

This is a 12 bolt car, right? Not a 12 bolt truck diff?
I am not 100% sure it was in the car when i bought it. All i know is that is really slips on corners worse when its hot almost sounds like a locker unlocking . plus like i mentioned its at least 15 years old with no repair just driving. Some people say a true locker is to much for the street
 

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All i know is that is really slips on corners worse when its hot almost sounds like a locker unlocking
If the clutches are burnt out and slipping, it turns into one wheel peel(like an open differential) straight line launch or cornering.....what you are describing with it making pops and clunks during cornering is clutches too grabby....not slipping.
Sometimes it takes a different brand of rear gear lube, and 2 bottles of additive for a big rear like the 12-bolt to get it to behave smoothly.
Especially in a light car like a Vega.

Can you be very descriptive about the behavior it has that you don't like....feel, sounds, etc.
What gear oil are you using?
Hate to see you replace a part that has nothing really wrong with it.

If it turns out you do need to replace it, My preference is like lmsport, use the True-Trac.
Ratcheting Lockers will sometimes have trouble unlocking around corners when the pavement is wet, and it can be rather scary if you aren't aware of it.
 

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True trac, full spool, or fully welded.
I usually just run full spool or Lincoln locker(welded).
You get some tire scrub. But it is better then wondering if the clicking the Detroit is doing at EVERY turn is a good or bad clicking.


I would weld up the 12 bolt and call it good. If you want to install a limited slip then Truetrac is the only limited I would install at this point. A full spool is less expensive then a Trutrac and offers variable spline options that a Lincoln does not.
 

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Discussion Starter · #14 ·
If the clutches are burnt out and slipping, it turns into one wheel peel(like an open differential) straight line launch or cornering.....what you are describing with it making pops and clunks during cornering is clutches too grabby....not slipping.
Sometimes it takes a different brand of rear gear lube, and 2 bottles of additive for a big rear like the 12-bolt to get it to behave smoothly.
Especially in a light car like a Vega.

Can you be very descriptive about the behavior it has that you don't like....feel, sounds, etc.
What gear oil are you using?
Hate to see you replace a part that has nothing really wrong with it.

If it turns out you do need to replace it, My preference is like lmsport, use the True-Trac.
Ratcheting Lockers will sometimes have trouble unlocking around corners when the pavement is wet, and it can be rather scary if you aren't aware of it.
yes it is very noisy and jerky but only there after a longer drive ( when hot) i guess its definitely clutch related > could be the oil is breaking down . i only use reg . oil not synthetic with 2 bottles of add. and i dont like the ratcheting noise either from a locker now that i have listened to one. so i think you are right the true trac may be the best option if clutches are bad. But will i loose the amount of rubber that i like to lay down from both wheels lol
 

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yes it is very noisy and jerky but only there after a longer drive ( when hot) i guess its definitely clutch related > could be the oil is breaking down . i only use reg . oil not synthetic with 2 bottles of add. and i dont like the ratcheting noise either from a locker now that i have listened to one. so i think you are right the true trac may be the best option if clutches are bad. But will i loose the amount of rubber that i like to lay down from both wheels lol
Have you considered just rebuilding the clutched posi unit you have??
The parts are available and not all that expensive.

If your going to replace it, and If it needs to be quiet and seamless, the True-Trac is your best option.
It'll handle more power and more driver abuse than a clutch type posi differential will
 

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Discussion Starter · #16 ·
Have you considered just rebuilding the clutched posi unit you have??
The parts are available and not all that expensive.

If your going to replace it, and If it needs to be quiet and seamless, the True-Trac is your best option.
It'll handle more power and more driver abuse than a clutch type posi differential will
ya i am going to price one out along with the rebuild kit .parts are more expensive in canada ive seen the True Trac listed here for about 900 -1000
 

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There is a reason why rearends are built with differentials. I'd replace the clutches you have with new ones and they should last a long time for street driving (no water burnouts) type use. Any rear that uses clutches will eventually need the clutches replaced, but they normally last a long time if you don't do water burnouts The Detroit Locker is noisy and irritating for normal driving...........but some claim to like it. Many people have installed them only to remove them later because of the noise. That part is a personal choice. There are rear ends available that don't use clutches, are quiet and long term reliable. Cost wise, I'd just put new clutches in what you have.
 

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I own two cars w/ lockers, a street machine w/ a Detroit and a Jeep w/ a lunchbox locker up front, also my pickup previously had a rear locker.

I'd advise against one for a cruiser. You're often "between clicks" driving w/ one wheel doing all the work, on the highway if you suddenly hit the throttle you get the car pulling one way or the other and it's a bit freaky especially at speed. On wet pavement on a corner, the inside tire takes all the torque then slips and the outside wheel gets it, and it's easy to fish-tail when you didn't want to. With the truck, the rear locker was the previous owner's bad idea, I used it for vacation towing of a travel trailer on steep curvy roads and (I believe) the constant condition of one inside tire doing all the pulling work resulted on both tires destruction at the sidewalls eventually, long before the tread would have worn out. That's not applicable to a street machine, still, I'd rebuild the posi. The Jeep with the locker only in the front and normally un-driven has an 8" posi rear and that works pretty well.

I don't know how anybody who understands automobiles (or safety) could use or recommend a spool or welded spiders on the street. Beats me.
 
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