TheAMCForum.com Homepage
Forum Home Forum Home > The Garage > Transmission & Drivetrain
  New Posts New Posts RSS Feed - Differential Block
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Click for TheAMCForum Rules / Click for PDF version of Forum Rules
Your donations help keep this valuable resource free and growing. Thank you.

Differential Block

 Post Reply Post Reply
Author
Message
Rambler Mexicano View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Mar/05/2011
Location: Guadalajara
Status: Online
Points: 970
Post Options Post Options   Thanks (0) Thanks(0)   Quote Rambler Mexicano Quote  Post ReplyReply Direct Link To This Post Topic: Differential Block
    Posted: Sep/07/2018 at 12:53am
Anyone knows either the PROs/CONs or the Facts/Myths on the differential block?

I have a 1981 VAM Rally GT (Spirit GT) that I will be using mainly for street and highway, I do not plan to use it at the dragstrip, competition or anything like that.

Yet, I am looking forward to make the car as powerful as possible even above the original 172 net HP specs.

One of my main interests is to give the car the highest acceleration possible, which I mainly plan to use to get away from any threatening situation or at least better passing in both the street and highway.

While asking friends and mechanics on this I was told about putting differential block on my car. This is that I was told:

At a standstill, the differential block locks the two rear tires and they both accelerate at the same time, being a huge improvement or single-wheel acceleration.

And after a short while (and certain speed), the differential block disengages by itself and the differential once again works as a one-wheeler.

I don't plan to have any form of permanent two-wheel traction. Only improved acceleration.

When I told this to my brother he told me not to use the differential block because at highway speeds it might engage on its own and will cause me to spin on the first curve and probably end up crashing. That the differential block is pretty much only for drag racing cars mainly, he said

Now I don't know what to think.

How much of this is true?

What do you suggest to get an excellent take-off with my car?

Thanks in advance.
Mauricio Jordán

Cuando no se es una empresa famosa se deben hacer mejores automóviles.
- Vehículos Automotores Mexicanos S. A. de C. V.
Back to Top
jpnjim View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Nov/25/2007
Location: New England
Status: Offline
Points: 2752
Post Options Post Options   Thanks (0) Thanks(0)   Quote jpnjim Quote  Post ReplyReply Direct Link To This Post Posted: Sep/07/2018 at 4:41am
I don't think the word "differential Block" is used here in the USA,
but he could be talking about what we call a "lunchbox locker", or a Lockright.

I lost track of all the companies making drop in lockers for stock open differentials,
but what they do is make a stock open case diff work like an automatic locker (similar to a Detroit Locker).

They are fine at highway speeds, though they can engage on the highway and effect short wheelbase vehicles like CJ5's,
the longer the wheelbase the less effect they have.
It's really just a minor annoyance that you can feel it kick in sometimes,
usually its the noise people complain about.

I ran a lockright in my Jeep's front axle and it was never a problem for me,
in the rear I had a full Detroit and that was no problem 99% of the time,
then it would slam open/closed around a random turn and you'd think the whole rear end came out of the vehicle LOL

They also make drop in "mini-spools",
those just engage both axles all the time,
I ran a full spool on the street for about 2 years and that really takes some getting used to.
Not recommended for a daily driver unless you like the attention from squeeling tires around tight turns.

Last point,
any type of drop in differential aid that fits in the stock open carrier is only as strong as the stock carrier.
Full case lockers, spools, and limited slips are almost always stronger than a drop in that fits the stock carrier.

Good luck.
71 P-code 4spd Javelin/AMX
some Jeeps and some Fords
Back to Top
jpnjim View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Nov/25/2007
Location: New England
Status: Offline
Points: 2752
Post Options Post Options   Thanks (0) Thanks(0)   Quote jpnjim Quote  Post ReplyReply Direct Link To This Post Posted: Sep/07/2018 at 4:47am
71 P-code 4spd Javelin/AMX
some Jeeps and some Fords
Back to Top
Rambler Mexicano View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Mar/05/2011
Location: Guadalajara
Status: Online
Points: 970
Post Options Post Options   Thanks (0) Thanks(0)   Quote Rambler Mexicano Quote  Post ReplyReply Direct Link To This Post Posted: Sep/07/2018 at 2:48pm
Thanks guys,

I translated it literally from Spanish in the way we say it here, now I see the accurate way to say it would be "locking differential".

Now I see it's not as dangerous as they made me see it.

Thanks for the links, I'll check them out.
Mauricio Jordán

Cuando no se es una empresa famosa se deben hacer mejores automóviles.
- Vehículos Automotores Mexicanos S. A. de C. V.
Back to Top
farna View Drop Down
Supporter of TheAMCForum
Supporter of TheAMCForum
Avatar
Moderator Lost Dealership Project

Joined: Jul/08/2007
Location: South Carolina
Status: Offline
Points: 19611
Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Sep/07/2018 at 9:00pm
But that type of locking differential is noisy and not real good for street use. What you really want is a limited slip differential. The AMC Twin-Grip. There are some aftermarket ones, but an original AMC Twin-Grip carrier would be nice. They work in much the same way as the locking differential but use clutches that slip some instead of a rather sudden lock. So one wheel would start spinning then the diff will lock and both will spin, but with a slight delay, and not  a sudden grab, because the clutches allow a little "give" before locking.
Frank Swygert
Back to Top
Rambler Mexicano View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Mar/05/2011
Location: Guadalajara
Status: Online
Points: 970
Post Options Post Options   Thanks (0) Thanks(0)   Quote Rambler Mexicano Quote  Post ReplyReply Direct Link To This Post Posted: Sep/10/2018 at 11:19pm
Thanks a lot Frank,

That was exactly what I want for my car. Limited slip slip differential.

I will talk to my trusted mechanic if it can be done with parts available here in Mexico, if not then I would probably have to buy an AMC Twin Grip from the US to put in my car.

Would this be a conversion or I would have to change the entire differential? My car has a SPICER model 44 unit with 3.31:1 rear gear ratio.

What parts would I need to make my differential a Twin Grip?
Mauricio Jordán

Cuando no se es una empresa famosa se deben hacer mejores automóviles.
- Vehículos Automotores Mexicanos S. A. de C. V.
Back to Top
farna View Drop Down
Supporter of TheAMCForum
Supporter of TheAMCForum
Avatar
Moderator Lost Dealership Project

Joined: Jul/08/2007
Location: South Carolina
Status: Offline
Points: 19611
Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Sep/11/2018 at 3:08pm
That would be a Dana 44 here in the US (Dana and Spicer are the same company, Spicer name used in some countries, Dana in others, many use Dana-Spicer). AMC used a different model, either the AMC 15 (Dana 35) or AMC 20 (no comparable Dana-Spicer axle). There are be limited slip units available for a Dana-Spicer 44. Search "Dana 44 limited slip" and you will come up with several options.
Frank Swygert
Back to Top
 Post Reply Post Reply
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.03
Copyright ©2001-2019 Web Wiz Ltd.

This page was generated in 0.141 seconds.
All content of this site Copyright © 2018 TheAMCForum unless otherwise noted, all rights reserved.
PROBLEMS LOGGING IN or REGISTERING:
If you have problems logging in or registering, then please contact a Moderator or