Ask the kid in the back of your van for that answer.Originally Posted by turbovanman
Wow, where's the love?
Ask the kid in the back of your van for that answer.Wow, where's the love?
Bryan
86 GLHS #161, 2016 Impala
SDAC National Member, SDAC Buckeye Chapter Member
A man has got to know his limitations.....
That's correct. The PTU ratio is 3.42:1 and the rear is 3.45:1. It needs that difference so the BOC(Bi-directional Overrun Clutch) operates as designed. The BOC is used in the '01 and later Caravans/Pacificas, the pre '01 vans used more of a sprag type of clutch. In the case of the pre '01 vans, if you were to engage the dog clutch in forward, you would have to calculate the overall gear ratio with tire size if using the stock rear.
Carlos
You guys know that the diff ratios are slightly different front to back right
Nope nothing is taxed the overrunning clutch is free wheeling until the front tires slip enough then the the viscous comes into action. Its quite clever actually.
Dean Stillie
87 Shelby Z 2.4 Turbo 9.06@146.05
82 Rampage 2.4 Turbo 10.14@138.02
All the more reason to leave it alone! Let the over running clutch do it's job and all will be well with the world!
similar AWD platforms over here that don't have the clutch do have a habbit of shredding VCs. The Land Rover Freelander is a prime example.
Does VC equal valve cover or viscous coupling in this case? lol
Bryan
86 GLHS #161, 2016 Impala
SDAC National Member, SDAC Buckeye Chapter Member
A man has got to know his limitations.....
Have you ever seen a shredded valve cover? Post pics.
Dont push the red button.You hear me?
lol, yeah, i meant valve cover
On a DD car i think it would be sensible to leave the clutch in, on a limited use/track car there is probably no point having it
copy/paste - http://www.ashcroft-transmissions.co.uk Freelander
"The Freelander has 3 main drivetrain problems areas, the Intermediate Reduction Drive (IRD), Viscous Coupling (VC) and the rear differential.
The reason for this is the front wheels on the Freelander are driven faster than the rear wheels so it handles well, like a front wheel drive car. To accommodate this ratio difference, a VC is fitted inline with the rear propshaft which thus is constantly slipping.
On the earlier models this ratio difference was too great resulting in the viscous coupling working overtime and failing by siezing solid. When the viscous coupling is too tight or seized solid the front tyres are fighting the rears as the transmission is "winding up", initially this just wears the tyres (causing a "saw tooth" effect) but it also puts increased load on the IRD and rear diff as they are fighting each other causing rapid wear on both and ultimately failure of one or both."
OUCH!! That sucks!!
Someone pointed out that the leaf springs of a Rampage simplify things . . . .
If the PTU ratio is 3.42:1, to go AWD with a Rampage, it seems like what I need for starters is a Mopar PTU and a 3.42:1 live axle/diff from some random mini truck . . . .
What random mini truck (or RWD light sedan) would that be? I'd get the brakes, shackles and drive shaft too . . . . Is there a data base of rear end ratios and track (axle lengths) by make & model?
John Laing
"The sole condition which is required in order to succeed in centralizing the supreme power in a democratic community, is to love equality, or to get men to believe you love it. Thus the science of despotism, which was once so complex is simplified, and reduced . . . . to a single principle."
-- Alexis de Tocqueville
"One of the methods used by statists to destroy capitalism consists in establishing controls that tie a given industry hand and foot, making it unable to solve its problems, then declaring that freedom has failed and stronger controls are necessary."
--Ayn Rand
"To evolve, you don't need a Constitution. All you need is a legislature and a ballot box . . . . things will evolve as much as you want. All of these changes can come about democratically; you don't need a Constitution to do that and it's not the function of a Constitution to do that."
-- Justice Antonin Scalia
I don't know that I would trust any of the small rear axles from the small trucks. Would it be easier to just use the setup from the mini? They used leaf springs too.
Bryan
86 GLHS #161, 2016 Impala
SDAC National Member, SDAC Buckeye Chapter Member
A man has got to know his limitations.....
The BOC(Bi-directional Overrunning Clutch) is incorporated into the rear assembly of '01 and later AWD Caravans/Pacificas/T&C is really needed to make the system work reliably. The slight difference between the transfer case and the rear differential (a whopping .03) keeps everything alive and out of a bind until the front slips, locks the BOC(Bi-directional Overrunning Clutch) and the rear differential provides the traction.
Off the top of my head, I'd say a 10 bolt from an S-10, etc. Maybe an 8.8 from a Ranger/other Ford. I doubt any will drop in, but at least these are fairly common and used in enough hot rod projects to merit the aftermarket making a variety of gears... Or you could just bolt in the stocker, four bolts and some reinforcement to the bed... OK, maybe a little bit more that that, but...
Mike
"The Constitution is not an instrument for the government to restrain the people, it is an instrument for the people to restrain the government - lest it come to dominate our lives and interests." - Patrick Henry
Bad laws are the worst sort of tyranny.
- Edmund Burke
An 8 3/4" from an early A body is within 1/2" of the L-body rear axle width. Too bad people think they are gold.
“If the people of the nation understood our banking and monetary system, I believe there would be a revolution before tomorrow morning.” -Henry Ford
In the '01 and later AWD, are the rear wheels disengaged by the BOC until the moment of front wheel slip? Or, are they . . . . ?
And, that 3/100ths difference in ratio . . . . seems like it would keep the wheels/chassis loaded in slight compression, or is it extension?, just barely working at cross purposes . . . . Is that load necessary to self power, to provide the energy to drive the BOC's action?
And then, there's no LSD in the front/primary transmission, right? but there is in the rear diff right?
John Laing
"The sole condition which is required in order to succeed in centralizing the supreme power in a democratic community, is to love equality, or to get men to believe you love it. Thus the science of despotism, which was once so complex is simplified, and reduced . . . . to a single principle."
-- Alexis de Tocqueville
"One of the methods used by statists to destroy capitalism consists in establishing controls that tie a given industry hand and foot, making it unable to solve its problems, then declaring that freedom has failed and stronger controls are necessary."
--Ayn Rand
"To evolve, you don't need a Constitution. All you need is a legislature and a ballot box . . . . things will evolve as much as you want. All of these changes can come about democratically; you don't need a Constitution to do that and it's not the function of a Constitution to do that."
-- Justice Antonin Scalia
I may be wrong, but the BOC is kinda like a bicycle sprocket (non-coaster brake), since there is a slight difference in ratios the rear is slipping so long as the front and rear wheels are spinning at the same rate, if the front looses traction, the PTU /diff speed becomes high enough to "catch-up" the rear, bringing it into play via the BOC.
No LSDs front or back in the stock set-up, the rear wheels/diff acts like one though.
Mike
"The Constitution is not an instrument for the government to restrain the people, it is an instrument for the people to restrain the government - lest it come to dominate our lives and interests." - Patrick Henry
Bad laws are the worst sort of tyranny.
- Edmund Burke
That setup with a solid rear axle would leave a lot of unsprung weight. It wouldn't handle as well as as the minivan setup, but would be better at the 1/4 mile.
Bryan
86 GLHS #161, 2016 Impala
SDAC National Member, SDAC Buckeye Chapter Member
A man has got to know his limitations.....
I agree with that, as I'm sure Allan would, what with the rave reviews he's given about the light wheels helping the ride and handling...
Aside from shortening the drive axles and fabricating/adapting hubs that have the hole for the axle, the stock van set-up will be the easiest to adapt and is a known quantity...
Mike
"The Constitution is not an instrument for the government to restrain the people, it is an instrument for the people to restrain the government - lest it come to dominate our lives and interests." - Patrick Henry
Bad laws are the worst sort of tyranny.
- Edmund Burke
Should be able to have the axles redrilled for the smaller bolt pattern, but don't know how much it would cost. Just in case adapters could not be used due to availability or not enough room in the chassis.
A dual bolt pattern rim could be used to mark the locations for the smaller pattern to save some $$$$. The hardest part would be getting the holes drilled dead center. A machine shop should be able to do that for little $$$$.
Bryan
86 GLHS #161, 2016 Impala
SDAC National Member, SDAC Buckeye Chapter Member
A man has got to know his limitations.....
the caravan rear beam doesnt look to bad either for making trailing arms that attach to it. it has 4 huge bolts that normally attach the leaf springs to it and they'll work well as trailing arm attachment points.
the center part is basically a pipe so cutting that, pressing in a piece of tubing in the center of the cut and welding it back up wont be hard either depending on how much it needs to be narrowed. i gotta take a tape measure out to the garage and measure the difference in length from brake disc hat face to brake disc hat face.
i havent measured it out totally, but it shouldnt be too bad to make a lower perch for the stock springs/shocks on non-l-body cars.
Brian
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