I had whining in the front end my mechanic determined it was the differential so he replaced the whole assembly from a low mileage vehicle, for some reason he felt the transfer case needed to be replaced as well. Shortly after these repairs I burned up the rear differential and it was replaced. This time he found a "matching" set front and rear and installed them both. I had driven a few hundred miles on the highway after the latest repair and the front differential failed again (loud whining and some smoke coming off the case). I was closer to my destination when this happened so I had another shop rebuild the front using all new parts. That shop drove the vehicle for a week or so to break in the new parts, when I picked it up and began my drive home it failed again in the same manner. What can be causing all this destruction and headache?
I'M ATTEMPTING TO FIND OUT ALL THE INFO I CAN FOR YOUR RIG
I NEED LOTS MORE INFO ABOUT IT
1) CHEROKEE XJ ('84-'99) OR GRAND CHEROKEE ZJ, WJ ('93-'99)?
2) TRANNY AND TRANSFER CASE TYPE?
3) AWD OR PART TIME 4X4. OR WHATEVER!
I'M REALLY GUESSING THAT THEY USED THE SAME RATIO ON THE FRONT AS THE REAR HAS
I'M FINDING THE XJ USED A (DEPENDING ON YEAR, ENGINE SIZE, AND OPTIONS) ---3.073.554.11----3.73 GEAR RATIOS
THE ZJ, WJ USED 3.54----3.73 GEAR RATIOS
THE OLE COMANCHE (MJ) USED---3.07---3.55----4.104.56 GEAR RATIOS
ON MY BABIES (THE CJs) I'VE SEEN IGNORANT OTHERS JUST GRAB UP AN AXLE AT AN AUTO SALVAGE YARD AND INSTALL IT, IN DESPERATION ONLY TO FIND OUT IT WORKED FINE. TILL THEY PUT IT INTO FOUR WHEEL DRIVE
THEY FOUND OUT QUICK THAT 2 WAY APART RATIOS BIND AND BUCK AGAINST EACH OTHER. AND JUST DON'T WORK!
HAD THEY BEEN "CLOSER" RATIOS. AND ON A DIRT ROAD/ SNOW/ SAND/ WET. WHICH WOULD ALLOW "SLIGHT BINDING" TO SLIPTHIS WOULD WORK. LIKE A 4.10 COUPLED WITH A 4.11OR A 3.54 COUPLED WITH A 3.55
EVEN PERFECTLY MATCHED RATIOS, AS ON MY CJ, 3.54 ON THE BACK---3.54 ON THE FRONT----STILL SHOULD NOT BE DRIVEN IN 4X4 ON IMPROVED SURFACES
I DON'T KNOW A BUNCH ABOUT THE AWD (ALL WHEEL DRIVE). WHICH I RECKON WORKS MUCH LIKE "TRAC-LOC" ON SOME CJs
SOME HOW OR ANOTHER, IN THESE SYSTEMS THE TRANSFER CASE DESIGN KEEPS THE FRONT AND REAR FROM BINDINGAND THE FRONT AND REAR RATIOS ON THESE VEHICLES ARE SUPPOSED TO BE EXACTLY THE SAME. NOT CLOSE!
I DON'T HAVE A CLUE WHERE THE PARTS FOR THE 1ST REPAIR CAME FROM----XJ---ZJ--WJ---MAYBE A COMANCHE?
. OR WERE THEY NEW PARTS. WRONG RATIO NEW PARTS. WRONG RATIO OLD PARTS?
AS AN EXAMPLE OF DIFFERENT RATIOS---THIS CAN BE DONE WITH DIFFERENT SIZE TIRES ON THE FRONT OR BACKOR EVEN EITHER SIDE (WHICH MAKES THE DIFF THINK IT'S CONSTANTLY IN A TURN!)
LETTING SOME OF THE AIR OUT OF THE FRONTS CHANGES THE GEOMETRY
NOW A CJ 2 WHEEL DRIVE EXAMPLEMINE'LL DRIVE "ALL DAY LONG" WITH 2 DIFFERENT FRONT TIRES LETS SAY A 20 INCH ON ONE SIDE AND A 25 INCH ON THE OTHER (WITH THE HUBS UNLOCKED) AND 2 TIRES THE SAME SIZE, ON THE REAR. LET'S SAY BOTH BEING 30 INCH.
ALL DAY LONG!TILL I JUMP OUT AND LOCK THE HUBS IN----AND PUT IT IN FOUR WHEEL DRIVE. THEN THINGS START BREAKING/ BINDING/ BUCKING
ON A SMALLER SCALE---STUPID EXAMPLEYOURS WITH A 4.11: 1 ON THE FRONT AND A 4.10: 1 ON THE REAR (HOWEVER IT GOT THAT WAY)
YOU ARE IN AWD?----YOU ARE NOW IN A "TINY" BIND----BUT STILL A BIND YOU WOULD NOT BE IN IF YOU HAD THE CORRECT RING AND PINION UP FRONT. MAYBE THE TRANSFER CASE "TRIES" TO COMPENSATE FOR THE BIND, BUT IT'S JUST TOO MUCH?
MAYBE 3RD AXLE WAS FIXED LIKE THE 2NDBUT NEITHER NEVER LIKE THE CORRECT 1ST ONE?
HAVE I BOGGLED YOUR MIND?
THIS IS JUST MY THOUGHTS ON POSSIBILITIESCOULD BE YOU HAVE "MY LUCK" AT THE MOMENT
March, 24, 2013 AT 5:07 AM
This is a Grand Cherokee Limited AWD, not sure what transfer case it had originally or put in, both differentials were off used grand cherokees and the gears do match, my thought is that maybe the transfer case that was installed was for a part time system, could that matter?
March, 24, 2013 AT 5:37 AM
THAT WOULD MATTER!
LIKE I SAID---NOT SUPPOSED TO DRIVE MY P/T 4X4 CJ ON HARD IMPROVED SURFACES---SAME GOES FOR OTHER P/Ters
I WAS READING IN ONE OF MY JEEP BOOKS----I REMEMBER SEEING SOMETHING ABOUT AN "AWD MODEL" THAT ALSO HAD A 2WD OPTION TRANSFER CASE (I DON'T THINK IT WAS YOURS)
THE BOOK I'M LOOKING AT IS THE "BUYERS GUIDE", LAST ROW--MIDDLE BOOK IN MY PIC. LOTS OF INFO ON WHAT WAS IN WHAT, AND WHEN. ALL THRU THE YEARS
HOW WOULD YOU LIKE TO ACCESS THE FACTORY MANUALS?
THEY MIGHT AID YOU NOW, AND FAR INTO THE FUTURE!
I SORTA STUMBLED ONTO THEM WHILE LOOKING FOR A PART ONE DAY----I HAVE THE ORIGINAL PAPER 1979 AMC FACTORY SERVICE MANUAL----IT IS ABSOLUTELY THE BEST-US MANUAL I HAVE !
TOP LEFT IN MY PIC---TATTERED, TORN, MISSING BOTH COVERS---I WISH I HAD TAKEN BETTER CARE OF IT, SINCE IT FELL INTO MY LAP IN 1984
YOUR YEAR/ OR UP OR DOWN ONE, CAN BE LOOKED AT, AND PRINTED FROM ONLINE. FOR FREE!
TOO BAD WE DIDN'T HAVE THIS KINDA DEAL WHEN I WAS WORKING ON MY 1ST 5 CJ 5s
March, 24, 2013 AT 7:58 PM
Hi guys. Sorry for butting in but there's something I haven't seen mentioned yet and that's tire size. There were some Jeeps and some Chevy Astro Vans that had all-time-four-wheel-drive and they will develop serious problems if all four tires are not exactly the same circumference. Even buying two new tires at one time and two matching tires a month later is unacceptable because being from a different run, they could be from a different factory, different assembler, or even have a different rubber composition. You absolutely must buy four tires at the same time.
Normally a single mismatched tire puts stress on the transfer case and takes that out, but with multiple failing differentials you have to wonder if the same cause is involved.
All-wheel-drive vehicles like Caravans and Aerostars are different than four-wheel-drive vehicles. Besides the fact they don't have a transfer case, they use a viscous coupling that allows the front and rear axles to turn at different speeds. There you would get away with a slightly different gear ratio if there was such a thing. The ratios must be exactly the same with all-time-four-wheel-drive. Your mechanic would have checked the ratio and would not have put in something different. I would be nervous about any mechanic rebuilding a differential. Even with the manufacturer's service manual, special tools and procedures are needed and precisely adjusting preload, backlash, pinion depth, and tooth contact pattern are critical in preventing noise from developing and the unit overheating. Rebuilding a ridiculously complicated high-tech engine is easier than rebuilding a differential that is going to see highway use.
March, 24, 2013 AT 8:56 PM
THANK YOU DOC
HEARING THIS FROM A "PROFESSIONAL TEACHER" SURELY SOUNDS BETTER THAN FROM A SOMEWHAT "HICK-A-FIED". BUT STILL AN EXCEPTIONAL JEEP CJ FELLER
I SORTA TRY TOO HARD EXAGGERATING THE TIRE HEIGHTS WITH BIG NUMBERS. WHEN LITTLE DIFFERENCES DOES THE SAME THING. MIGHT JUST TAKE MORE TIME. AND THE "BINDING" GOES UN-NOTICED
THE OWNER'S MANUAL MAY ALSO TALK ABOUT THIS. NOT TOO MANY LOOK AT IT TILL THEY NEED TO FIND A FUSE LOCATION OR SOMETHING
I'VE YET TO LOOK IN THE FACTORY MANUALS FOR THIS MODEL----I'VE BEEN TRYING TO ANSWER OTHERS AS WELL. BUT I WILL SOON, WHEN I GET A LITTLE MORE MOTIVATED
I LIKE TO GET AT LEAST ONE RESPONSE WITH THE CJ GUYS, SOMETIMES OVER 100.I ALWAYS WONDER IF I'M HELPING IN ANY WAY