Noisy Ta­coma truck could be easy fix

Winnipeg Free Press - Section F - - AUTOS - JIM KERR

QUES­TION: We have a 2006 Toy­ota Ta­coma Sport 4x4 with 100,000 km. We pur­chased it new. Of late, we have not been driv­ing it as the prob­lem that ex­ists is an­noy­ing, if noth­ing else. When driv­ing the ve­hi­cle, there is a sound like that of a whis­tle from a ket­tle that ap­pears to be com­ing from the pas­sen­ger side rear.

A tech­ni­cian, who worked for a Toy­ota deal­er­ship and now has his own busi­ness, took our ve­hi­cle for a ride and sub­se­quently put it on his hoist, us­ing a scope to iden­tify what he be­lieved was the prob­lem. It was de­ter­mined that the prob­lem was the bear­ings in the dif­fer­en­tial.

New bear­ings were put in the ve­hi­cle and the owner/tech­ni­cian de­ter­mined that the prob­lem was fixed. Well, we took the ve­hi­cle to go shop­ping (round trip of 115 km) and, right from the start, the whis­tle sound was still there. We took it back and the shocked tech­ni­cian can’t be­lieve the prob­lem still ex­ists. He is at a loss as to ex­plain what it could be. Any rec­om­men­da­tions to solve our prob­lem?

AN­SWER: Toy­ota has a cou­ple of bul­letins out re­gard­ing dif­fer­en­tial noise on your year of Ta­coma. The re­pair in­cludes re­plac­ing the dif­fer­en­tial and in­stalling sound-dead­en­ing ma­te­ri­als be­neath the car­pet in the rear cab area. Be­cause the bul­letin re­quires they re­place the com­plete dif­fer­en­tial in­stead of just bear­ings, I would as­sume the noise is caused by the gearset wear pat­tern, which in turn may have been caused by a bad bear­ing.

Di­ag­nos­ing this type of prob­lem can be dif­fi­cult, be­cause the noise may not be present or be dif­fer­ent when there is no load on the driv­e­train, such as oper­at­ing the ve­hi­cle on a hoist. Driv­ing down the road with the weight on the wheels and torque through the bear­ings and driv­e­train com­po­nents will typ­i­cally cause the noise to be more pro­nounced.

Be­fore you spend a lot of money on the rear axle, there are a cou­ple other items to look at. Check that any dust shields on the dif­fer­en­tial pin­ion and drive­shaft are not close to touch­ing any other parts. Even if the parts are not touch­ing but only close, it can cre­ate a whistling/howl type sound at speed.

Also, re­move the drive­shaft and in­spect each u-joint for rough­ness or bind­ing. A u-joint that has brinelled (wash­board wear pat­tern usu­ally caused by load or im­pact) can cre­ate a noise sim­i­lar to what you de­scribe. Hope­fully the prob­lem is in this area and will be easy to fix.

QUES­TION: A tech­ni­cal ques­tion con­cern­ing tur­bocharg­ers was an­swered in the Novem­ber 2012 is­sue of Road and Track. One line in the re­ply to the writer’s ques­tion caught me by sur­prise. (The ques­tion re­lated to the Ford Fo­cus Ecoboost engine but I as­sume it ap­plies gen­er­ally.)

The au­thor stated the de­sign life of a ve­hi­cle is 150,000 miles (250,000 km in our units.) This seems rather “un­op­ti­mistic” to me. I like to keep my ve­hi­cles for at least 10 years and the last was run­ning great af­ter about 350,000 km.

What does de­sign life mean? Is this when ma­jor re­pairs can be expected to oc­cur? If they are de­signed to last this long, why are war­ranties so low in com­par­i­son? How does this value for de­sign life com­pare to ve­hi­cles man­u­fac­tured a gen­er­a­tion ago?

AN­SWER: The de­sign life of a ve­hi­cle com­po­nent is an engi­neer­ing es­ti­mate. In your ex­am­ple, the tur­bocharger was in­di­cated to have a life of 250,000 km. This is un­der typ­i­cal driv­ing con­di­tions with nor­mal main­te­nance. I have heard them talk of a de­sign life of 350,000 km for some of the diesel engine tur­bocharg­ers.

These es­ti­mates of life­span would in­di­cate when a ma­jor re­pair may be needed to main­tain the orig­i­nal per­for­mance level of the ve­hi­cle. Of­ten, you can drive much fur­ther but per­for­mance may be de­creased. In my ex­pe­ri­ence, most ve­hi­cles will last far be­yond the “de­sign life.” Haul­ing heavy loads, tow­ing and per­for­mance driv­ing will all shorten the life of com­po­nents, so the de­sign life is meant to in­clude all com­mon uses of the ve­hi­cle.

As for com­par­ing this to ve­hi­cles built two or three decades ago, de­sign life wasn’t typ­i­cally dis­cussed back then, but look­ing at ve­hi­cle re­pair his­tory and us­age, new ve­hi­cles last much longer than be­fore and re­quire less-fre­quent re­pairs. Jim Kerr is an ex­pe­ri­enced me­chanic, in­struc­tor of au­to­mo­tive tech­nol­ogy, free­lance jour­nal­ist and mem­ber of the Au­to­mo­bile Jour­nal­ists’ As­so­ci­a­tion of

Canada.

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