Solving Common Noise Problems

Up To Standards

Subject: Diagnosing noise problems Solving Common in manual transmissions Essential Reading: Noise Problems, and Rebuilder Shop Owner Problems with Center Manager Diagnostician No Solutions R & R Author: Mike Weinberg, Rockland Standard Gear Contributing Editor

oise is one of the great myster- There is also the mysterious “never ies of the transmission world. had that before” noise. This noise usu- NNoise is subjective, and people ally comes to the customer’s attention rarely can interpret noises in the same as a result of a change of habits creat- manner. Noise travels much faster and ed by having shelled out a large sum farther in solid objects such as the steel to repair their vehicle. After such an of an automobile than it does in air. expense, the customer is driving the There is driveline noise, engine noise, vehicle with the radio off and all inte- suspension noise, exhaust noise and rior appliances such as A/C shut road-generated noise. down, listening intently to the trans-

Two-mass flywheel with sealed casing Two-mass flywheel, sealed casing

©2008 Transmission Digest. Reproduced with permission. For subscription information call 800-274-7890 Up To Standards mission they just paid for. Present gree. The best test for this type of harmonics and create customer are the normal tire and road-sur- noise is to start the engine, place complaints. face noise, wind noises and rattles the transmission in neutral, have Certain models of transmissions that have been with the vehicle for the clutch engaged (pedal up) and are highly prone to gear rattle, and many moons but are now readily slowly add throttle from idle speed to be successful in their repair one apparent to the driver, who no to 2,500-3,500 rpm. If it is gear rat- needs to fully inspect the clutch longer is listening to his favorite tle the noise will float out as the and flywheel components and the tunes at 120 decibels. engine speed increases. engine tune level. These transmis- Manufacturers go to great Gear rattle or neutral-rollover sions are the New Venture Gear lengths to produce vehicles with noise does not affect the operation 1500 in 2.2-liter GM 2WD trucks; very low noise levels. The car is of the transmission or do any dam- 2550 in 2.5-liter Jeep 2WD and tuned and insulated to get rid of age to the gear train, but you can’t 4WD models; 3500 in 4.3-, 5.0- and harmonic vibrations that cause dis- sell that to a customer who has just 5.7-liter GM and Dodge trucks; comfort for the driver. spent money on repairs. On larger 3550 in 4.0-liter Jeep 2WD and Transmissions and final drives are transmissions in pickup trucks you 4WD; 4500 in GM/Dodge trucks; designed with gear angles for can actually see it occur. Drain out and the 5600 in Dodge trucks. The strength and low noise generation. the lubricant and remove a power- ZF Ford truck transmissions, S5-42, Interiors are heavily insulated takeoff plate. Start the truck in S5-47, S6-50 and S7-50, and the against noise, vibration and harsh- neutral with the clutch engaged, Corvette S6-40 transmission also ness (NVH), and the entire chassis and watch the gears shake. have had gear-rattle complaints. is designed with various devices to Since this is not a transmission Once more, if it is gear rattle that make NVH occur at acceptable lev- problem, nothing you do inside the leaves with a slow increase in en- els to the driver. Any changes to transmission will make this go gine speed in neutral, no amount the chassis such as insulation or away. The cause is engine harmon- of disassembly of the transmission items left off during the installa- ics influencing the gear train. To will make it go away. tion of the transmission can open get rid of the noise we need to go the door for customer NVH com- to the clutch, dual-mass flywheel Problems with few or plaints. The carmaker is profit mo- or the engine running condition no solutions tivated, and no part installed on and sort that out. In 1988 GM introduced the HM the vehicle has no function; they Dual-mass flywheels have pri- 290 series of five-speed transmis- are all necessary. mary and secondary plates with sions for its C and K truck trans- The most-common transmission spring loading between them. If missions. Designed by Getrag, noise and the greatest waster of the springs have lost their tension, these were extremely over-engi- labor hours is neutral-rollover engine harmonics will rattle the neered designs, with too many noise. There is no such thing as a gears. parts (there were 96 pieces in the completely silent transmission. All On the clutch disc we will have shift mechanism alone) and requir- rotating parts create some level of damper springs on the hub that are ing special essential tools for re- noise and vibration. The engine calibrated to the engine firing puls- pairs. GM and Chrysler created a creates harmonic vibrations be- es to damp them from passing joint venture called New Venture cause of the firing pulses of each through to the transmission. Gear involving the GM Muncie cylinder. If these harmonic vibra- Installation of an incorrect clutch plant and the New Process Gear tions are allowed to travel into the disc for the application or hub division of Chrysler. transmission through the input dampers that are no longer func- As I had predicted in conversa- shaft, they cause the gear train to tional will create rollover noises. tions with engineers at Hydramatic rattle, and this is gear rattle or neu- The condition of the engine tune all those years ago, the HM 290 de- tral-rollover noise. The manufac- is critical to this discussion. Bad in- sign was a nightmare. The trans- turers do all they can to damp jectors, plugs or wires, or worn mission was redesigned and called these vibrations in the engines cams and timing chains can create the 5LM60, and this too proved to with balance shafts and dual-mass harmonics that no dual-mass fly- be problematic. A further redesign flywheels, and proper clutch-disc- wheel or clutch disc can stop from produced the second variation of hub damper springs. rattling the gears. On diesel en- the 5LM60, which still had four Gear rattle or neutral-rollover gines pay attention to the injector shift rails and the same problems. noise occurs in neutral with the pump, which is how diesels are The engineers at New Venture clutch engaged, and at various timed. A worn or out-of-time redesigned the latest version of the speeds in other gears to a lesser de- pump will greatly magnify engine 5LM60 into what you now know as

©2008 Transmission Digest. Reproduced with permission. For subscription information call 800-274-7890 Up To Standards the NV 3500, which was a single- The joint venture between the rail transmission. The unit had in- GM Muncie plant and the New ternal noise concerns that were not Process division of Chrysler has to be cured. The 3500 countergear ended. The GM Muncie plant has is supported by straight roller been closed and all the machinery bearings at the front and rear. sold off. Chrysler kept the New Without tapered roller bearings or Venture name for the New Process washers to shim the endplay on plant but no longer builds any of the shaft, there is no way of con- the previous models. trolling the endplay. Subsequently, Chrysler sold the These units frequently suffer New Venture/New Process from a tip-in clunk when the clutch Division to Magna International, a is engaged and a similar clunk on major tier-one OEM supplier. This coast-down when the clutch is re- partnership sucked $80 million to leased. This occurs because of ex- $100 million of profit out of New cessive movement of the Process Gear when it was owned countershaft due to the natural by Chrysler and produced a great tendency of helical-cut gears to try number of transmissions for which to move away from each other no OEM replacement parts are under torque and to contract to- available. When you have to re- gether when the torque load is re- build one of the units you now leased. This problem often results have to rely on aftermarket parts. 1 in as much as ⁄4 inch of endplay in Many of these parts are well made the shaft. and will give good service, but If you have a customer com- most of these Getrag-based de- plaint of tip-in clunk, remove the signs have noise issues that cannot oil drain plug, which is at the bot- be resolved. If you are working on tom of the transmission case. After one of these units discuss these is- the lube drains out, take a long sues with the customer so you flat-blade screwdriver and place it don’t wind up taking responsibili- on the counter gear and see how ty for something you did not cre- much endplay you have. This will ate. TD be your clunking noise, and we have found no way to cure it. I have seen a C truck in which a Chevy dealer installed five factory units with no good outcome, and GM finally bought the vehicle back under a lemon-law case. The NV 3550 is a variation of the 3500 that is used behind the 4.0- liter engine in Jeeps. This unit suf- fers from incurable gear rattle, gear jump-out and notchy, noisy shift- ing. There is one cure for this condition, and that is to replace the unit with an AX15, which is a di- rect bolt-in, using the same clutch set, hydraulics, cross member and driveshaft. Depending on the model and year of the Jeep it may be necessary to change the shifter and the input shaft of the transfer case. We have developed a kit for this replacement.