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CAD vacume system upgrade

Shogun

NAXJA Forum User
Since the posi-lock was a $500 waste of time I am back to the vacume system. Suffice to say the other common choices are not worth the trade off (solid axle, late model d30, hub locks).

I am looking to make sure the vacume system is as reliable as possible (upgrade/harden lines, carry spare diaghram). I am considering adding a seperate vacume reservoir just for the CAD and have a couple ?s.

1. Is the CAD currently using the vacume ball?
2. Will the CAD operate currently without the motor running?
3. Is there a downside to plumbing the CAD with a reservoir?
 
If your not using the vac canister it could be possible that that axle will unlock under WOT. I don't see a problem with just swapping in a non CAD axle. Fooling with the CAD tends to be a waste of time to begin with.
 
Jeeze just swap a solid axle and be done with it. Or if you really want to be cheap, slide the sleeve over both axles and keep it there somehow; have somebody tack a blob of weld to keep it from sliding back. Done. What's the tradeoff exactly? 0.5mpg better mileage?
 
Jeeze just swap a solid axle and be done with it. Or if you really want to be cheap, slide the sleeve over both axles and keep it there somehow; have somebody tack a blob of weld to keep it from sliding back. Done. What's the tradeoff exactly? 0.5mpg better mileage?

Gosh, I simply asked a question, having considered my options and limitations. I know I can install a solid axle, and I know I can get a LP D30 without the CAD.

The trade off is trying to locate a new header that get busted because the driveshaft is spinning all the time, and nobody makes them for 89/renix motors anymore. Or trying to locate a shop that will have the ability and inclination to cut and modify the present, no-longer available header. I can risk the damage when in 4wd because that time is limited and usually low-speed. So I want to avoid the full-time rotating front driveshaft.
 
Ok, if you want vacuum you can have it.

Want it totally reliable--not gonna happen.

Want it as reliable as possible--Ok, add a second reservoir just for the CAD/t-case, run hard lines everywhere, isolate the reservoir with check valves. Simple enough to do, Git R Done!

EDIT: don't forget to carry a spare vacuum motor and a spare vacuum switch for the transfer case.

PS--if you paid $500 for a Posi-Lok I hope you got dinner and flowers, and that the salesman used KY and a condom to close the deal.
 
What are you talking about? Is the driveshaft hitting the exhaust header??? Nobody makes header/manifold for renix jeeps??Get a non-disco axle shaft and block off plate with the correct seal and be done.........$500 ............. man coulda got an axle shaft and leave the stock CAD there ...BUT gut/cut off the shift fork and get a seal........it's been done before.:gag:
http://cgi.ebay.com/ebaymotors/89-9...ptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories
That s new header Renix 4.0!!!!
 
Vaccum = trash. Do the swap. And don't swap for a LP30 :doh: get the high pinion.

Pull the front shaft if it worries you that much. I'm not sure what you think the problem will be considering a thousand other people have solid HP30 swaps in their renix with no problems :dunno:

finding excuses to keep the cad and not do a solid HP30 swap is like justifying driving a pinto over a lambo "the power is just too unpredictable"
 
Lock the CAD over and forget about it. No strength increase but you get peace of mind knowing that the front axle is engaged and wont come or be disengaged when you need it most.
Simple to do. Pull cover. Remove C clip, slide fork over, reinstall C clip. Slide collar over on the axle. Plug unused vac lines. Reinstall cover with sealant. Check fluid level. Done.
15 min to half an hour.
Sealant
Oil, to top off diff.
 
EDIT: don't forget to carry a spare vacuum motor and a spare vacuum switch for the transfer case.

And a spare shift fork; I broke that on my old XJ twice before I gave up, slid the thingy over by hand, and put a bunch of tie-wraps on the axle to hold it there :D
 
The trade off is trying to locate a new header that get busted because the driveshaft is spinning all the time, and nobody makes them for 89/renix motors anymore. Or trying to locate a shop that will have the ability and inclination to cut and modify the present, no-longer available header. I can risk the damage when in 4wd because that time is limited and usually low-speed. So I want to avoid the full-time rotating front driveshaft.

:huh:
 
I think you'd be better off to switch to a manual cable actuator than to try to make the vaccum actuator reliable. The kits are not too expensive and will be far more reliable than the vaccum setup.
 
Well, I appreciate the interest and opinions. To satisfy everyones curiosity, here are further explanations;

A turning driveshaft is larger than a stationary one at the points where the U-joint yokes are located. You can orient the DS so the yolk either clears or hits something adjacent to the DS.

That something is the header. The Borla is one-piece, so there is no downpipe seperate from the header. Were it that simple, I could pull the downpipe and have it modified fairly simply. The contact has dented the header and in addition to the self-clearencing it places stress on the entire unit, which I suspect may eventually damage it further upstream.

Banks header will not fit, despite all the advice on this forum. Borla does well, but is no longer made. Other companies, at the time of install, were either unresponsive or unwilling to state whether thier product would fit the renix. So my takeaway assumption at this point is that there are no quality headers available for renix 4.0. I may be wrong, but that was the case several years ago. Either way, I dont want to intentionally ruin the header assy.

If the front DS turns, as it does on a solid axle, and I get any straight compression on the front suspension, there is a large crunch from the DS mashing the header pipe. I can live with that temporarily when in 4wd and going slowly, but not everyday speedbumps and cattleguards at 50 mph.

The posi-lock is NOT the bombproof solution you think it is, as I stated in the OP. At $200 for the part and $300 for install, it never worked. The company tried to distance themselves from the problem by blaming the installer, and the installer blamed the company. I dont want to throw good money after bad, so I pulled it out.

I know this subject is a bit of a nerve, I suspect because it may be a shibolith. Everyone just Knows the CAD is bad, it just is. And anyone that questions that "fact" must be a heretic. I've had it not work a couple times, mostly hose issues. Local advice says the switch sometimes fails, and rarely a fork. Well, Ive had the posi-lock fail twice and never work correctly. Does that make it junk? Most people think not. It may work fine for some folks, but failed me and the prospect for success in my case isnt worth the expense. I wanted peace of mind and I will never have it, even if they fixed it today. The difference is that I can fix the vacume system easily in the field. I cant fix the cable (but could jam it over if necessary) and cant fix a broken header.

From a system engineering standpoint, I understand that a vacume system is inherently less reliable than a solid axle. Its another entire system to install and maintain, vacume. But I dont see folks complaining about ARB lockers. It requires an entirely seperate system to purchase, install and maintain in order to operate the locker. And it has a known track record of failures. But yet, everyone clamors to buy it and sing its praises. From a systems standpoint, it is not much different from a vacume operated CAD, except that it is way more expensive and complicated. But we just KNOW its good. Shiboliths.

I would prefer to purchase a new D44, HP, trussed front end. But thats not in the cards. The vacume can work, it is cheap, and as reliable (or more so) as an ARB locker system. It is not the gold-plated, bomb-proof solution. But parts are inexpensive and easy to maintain. All I would like is to make sure the "system" is as reliable as possible by addressing the known weak spots, and keeping up with regular maintenence.
 
Making the "system" work correctly is one thing. But aren't you not addressing the "root" of the problem. Which is that your suspension in whatever configuration it is in shouldn't be allowing the DS to contact any engine or suspension parts ever. Well that's not including 3ft of air etc. myself, I'd be spending my money on the suspension before any more component damage then insure the 4wd system is doing it's job properly.
 
Soooooo root cause is a badly fitting header, as far as I can tell.

Solutions:

  • modify header to clear driveshaft
  • return to stock exhaust
  • increase lift
Anything else is a waste of time and money. $500 would have gone a long way towards a bigger lift.
 
If the header (expensive) is the root cause and you don't want it trashed, I'd suggest returning to a stocker (least expensive) until the suspension issue can be addressed. IMHO, the Renix isn't a high RPM motor, real performance increases aren't gained till the upper RPM ranges. Gains are usually netted along with other mods such as intake cam etc. For me, gears and tranny is where my best money is spent.
 
A statement was made about not hearing ARB people complaining about having vacuum/pressure lines break. Well you must not have been wheeling with many of them. It seems like on almost every trail I end up waiting because one broke. That said, you can do it right and not have problems, and when I say "it" I mean almost anything. I have run vacuum with no problems because I replaced the 15 year old lines with a $10 replacement from the dealer. I ran a cable actuated release that I built with little problem until I got away from D30s years ago.

The problem with the D30 is that if you have a lunchbox type locker, you really only get 3 wheel drive when it is disco'd. On slick rock it still plows in the tight corners. My favorite non engine mod was the Tera2Lo.
 
A statement was made about not hearing ARB people complaining about having vacuum/pressure lines break. Well you must not have been wheeling with many of them. It seems like on almost every trail I end up waiting because one broke. That said, you can do it right and not have problems, and when I say "it" I mean almost anything. I have run vacuum with no problems because I replaced the 15 year old lines with a $10 replacement from the dealer. I ran a cable actuated release that I built with little problem until I got away from D30s years ago.

The statement made was; they have a known trackrecord of failure, but still people love them. So does the vacume CAD, but its a "known" fact that they are junk.

You are correct that you can do it right. Thats my original intent. Spending $1000 for exhaust mods so that I can spend $1000 on axle mods, all just to avoid the vacume CAD appears silly when finances dont allow it. I think the vacume CAD can be made pretty reliable with a few low cost improvements like harder lines with good clamps, protected from trail damage, along with a dedicated vacume reservoir.
 
The statement made was; they have a known trackrecord of failure, but still people love them. So does the vacume CAD, but its a "known" fact that they are junk.

You are correct that you can do it right. Thats my original intent. Spending $1000 for exhaust mods so that I can spend $1000 on axle mods, all just to avoid the vacume CAD appears silly when finances dont allow it. I think the vacume CAD can be made pretty reliable with a few low cost improvements like harder lines with good clamps, protected from trail damage, along with a dedicated vacume reservoir.

something is really wrong if the CAD is dausing the DS to have an affect on the exhaust. if your DS is hitting the downpipe/exhaust manifold, then you need to bumpstop correctly or you need to loosen the exhaust clamps and reposition the down pipe.

is your front axle centered???

what lift and tire size are you running?

im still running the stock CAD on my 89 and all i did was trim the length of the hoses, used zip ties to keep them out of the way, and used hose clamps to secure them to the shift motor.

i just dont see why your having this problem.
 
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