Changing The Fluid

Its a messy job because theres no drain plug to change the fluid, but you can do it yourself if youre so inclined. To change the fluid, you have to get under your vehicle and remove the pan from the bottom of the transmission. When you loosen the pan, fluid will start to dribble out in all directions so you need a fairly large catch pan. You should also know that removing the pan doesnt drain all of the old fluid out of the transmission. Approximately a third of the old fluid will still be in the torque converter. Theres no drain plug on the converter so youre really only doing a partial fluid change. There is also anywhere from one to 3 quarts in your cooling lines and cooler.  The only way to remove that fluid is to pull the cooling lines off and blow threw it with a high pressure air hose. A typical fluid change will require anywhere from 3 to 6 quarts of ATF depending on the application, a new filter and a pan gasket (or RTV sealer) for the transmission pan. Since most transmissions hold 11-13 quarts, you can see that you are only able to change some of the fluid.  That is why taking your vehicle to a Transmission repair shop such as Transmission Clinics is so vital. You should also know that the pan must be thoroughly cleaned prior to reinstallation. This includes wiping all fluid residue from the inside of the pan and scraping all traces of the old gasket from the pans sealing surface. Dont forget the mounting flange on the transmission, too. When the new filter is installed, be sure it is mounted in the exact same position as the original and that any O-rings or other gaskets have been properly positioned prior to tightening the bolts. Then tighten the bolts to the manufacturers recommended specs. When refilling the transmission with fresh fluid, be careful not to allow any dirt or debris to enter the dipstick tube. Using a long-neck funnel with a built-in screen is recommended. Do not overfill the transmission. Too much fluid can cause the fluid to foam, which in turn can lead to erratic shifting, oil starvation and transmission damage. Too much fluid may also force ATF to leak past the transmission seals. Add half a quart at a time until the dipstick shows full. The transmission really isnt full yet because the dipstick should be checked when the fluid is hot, and the engine is idling with the gear selector in Park. So start the engine, drive the vehicle around the block, then recheck the fluid level while the engine is idling and add fluid as needed until the dipstick reads full.

Manual Transmission - Clutch Replacement

Q. I have a Manual Transmission (stick shift). When I am driving, the RPM gauge shows the engine is working hard but I am not moving as fast as I should be. (Clutch is starting to slip). Does that mean I need a new clutch?

A. If your clutch has low miles on it (25,000 or less), chances are the slippage is due to one of two things: oil or an improperly adjusted clutch linkage. If your clutch has a lot of miles on it (40,000 or more), chances are its worn out and you need to have it replaced.
To rule out oil contamination as a possible cause of slippage, check under the rear of the engine and the transmission housing(bellhousing) for oil residue. If you see oil on the ATF oil pan or bell housing, a bushing or seal is probably leaking. Other leak points include engine gaskets at the back of the engine, and the transmission input shaft seal. If youve got an oil leak, dont replace the clutch until youve fixed the leak. Once the clutch linings have been contaminated by oil, theres no way to clean them. Replacing the clutch disk is the only way to restore proper clutch operation. If you dont have a leak, check the linkage adjustment. Most cars with a cable linkage have an automatic adjusting mechanism thats supposed to maintain proper clearances. If anything, the cable would be too loose rather than too tight. But if someone has been playing around with the linkage adjustment, they may have gotten it too tight. The same goes for vehicles with hydraulic linkages. Theres no way this type of linkage can cause slippage unless it is improperly adjusted by someone. Slippage can be caused by two things: worn facings or loss of spring tension in the pressure plate. Normal wear reduces the thickness of the facings on the clutch disk, which in turn reduces the clamping force the pressure plate can apply to squeeze the disk against the flywheel. Replacing the clutch disk and pressure plate should cure the problem. If not, a throw out bearing or slave cylinder may be the culprit. Even so, the clutch and flywheel should be carefully inspected when the parts are removed. If the pressure plate is worn or damaged, youll need to replace that, too. Most experts recommend having the flywheel refaced to restore the friction surface. You can probably get by without refacing the flywheel -- but only if the flywheel is flat, smooth, clean and uncracked. Any grooves, heat discoloration, cracking or other damage would call for resurfacing or replacing the flywheel.

Q. Can I remove the transmission and replace the clutch myself?

A. You can replace the clutch yourself if you have the proper tools and know-how. Changing a clutch is a big job on a rear-wheel drive car or truck, and an even tougher job on a front-wheel drive or all wheel drive vehicle. On a rear-wheel drive vehicle, the driveshaft, transmission and cross mounts have to be removed from underneath the vehicle to get at the clutch. The clutch can then be unbolted from the flywheel and replaced. Resurfacing the flywheel is recommended -- and required if the flywheel is warped, grooved, badly worn, heat discolored and/or contaminated with grease or oil. That means the flywheel has to come out, too. If the flywheel is cracked, it should be replaced. In addition to replacing the clutch, a new throw-out bearing is also recommended. Considering the labor involved to tear everything apart, its risky to reuse an old throw-out bearing. It may not be noisy now, but its hard to tell how many miles it might have left in it. The pilot bushing in the end of the crankshaft that supports the transmission input shaft should also be inspected. Replacement is recommended if your vehicle has a lot of miles on it. Reinstalling the transmission is the most difficult part of the job because the transmission is heavy (which means youll need a floor or transmission jack, or a couple pairs of strong arms). The clutch must also be perfectly aligned (with a specially designed pilot tool just for that vehicle) so the transmission input shaft will slip into place, once everything has been bolted together. With front-wheel drive, replacing the clutch is even more difficult because it involves pulling the engine or dropping the transaxle (both of which are major undertakings because of all the disassembly thats involved). For this, youll need an engine hoist to pull the engine or a hoist or beam to support the engine from above while the transaxle comes out.

Q. My clutch chatters and feels jerky when I start out from a complete stop. Do I need a new clutch?

A. Chattering and jerking can be caused by oil contaminated clutch linings (due to an oil leak on the back of the engine, usually the rear main crankshaft seal), or by damage to the clutch itself. For the clutch to engage properly, the pressure plate must meet evenly on the disc. In other words, the surface of the pressure plate must be parallel to the flywheel otherwise it wont engage smoothly. If the flywheel is warped (which can happen as a result of overheating and abuse), it can make the clutch grab or chatter. On rare occasion, a manufacturing defect in a new or rebuilt clutch can cause uneven engagement as can improper installation of the clutch. If someone allows the weight of the transmission to "hang" on the clutch, it can bend the clutch disk causing shudder, grabbing or chattering. A damaged spline on the transmission shaft can cause the clutch disk to hang up and grab. You should also check for loose or broken motor mounts.

Q. I have a manual transmission. Does the fluid in it ever need to be changed?

Most Manufacturers recommend periodic lube changes for their gearboxes unless they use synthetic fluids, but most modern cars or light truck require it. The oil stays relatively clean and runs fairly cool in a manual transmission. Unlike the fluid in an automatic transmission that is being constantly churned (which generates heat) and contaminated by particles worn off the clutch plates, the fluid in a manual transmission or transaxle stays pretty cool. It usually lasts the life of the transmission. The only reason you might have for changing it would be if you were experiencing hard shifting problems during cold weather. Most older rear-wheel drive transmissions use a heavy gear oil like 75W, 80W or 90W, which can get pretty stiff at subzero temperatures. Changing to a lighter oil may improve shifting. Most manual transaxles in front-wheel drive cars today use Dexron II automatic transmission fluid (ATF) to keep the gears lubed. ATF works well because it stays much more fluid at low temperatures. But ATF should not be substituted for gear oil. Always use the type of lubricant specified by the vehicle manufacturer.

Adding Manual Transmission Fluid

The only time you should have to add oil to a manual transmission or transaxle is if their is a leak. If you see any grease or wetness around the tail or driveshaft seals, the oil level in the transmission or transaxle should be checked because it may be low. WARNING: Allowing the transmission or transaxle to run too low on lubricant can ruin it as fast as one mile.

Four/All wheel drive

Q. What's the difference between "automatic"(part time), "full-time" Four wheel drive and All Wheel Drive?

Part-time four-wheel drive (4WD) allows a vehicle to be driven in the two-wheel drive mode for ordinary highway and everyday driving (which reduces drive train friction and tire wear for improved fuel economy and tire life), and allows it to be switched to four-wheel drive when extra traction is needed (as when driving off-road, on gravel, snow, ice or mud). Vehicles with part-time four-wheel drive may have manual or automatic locking hubs on the front wheels that must be engaged to change from two-wheel to four-wheel drive. With manual locking hubs, you have to get out of the vehicle and twist a knob on both hubs to engage the front wheels. On some vehicles, the hubs engage and lock when the vehicle is driven backwards momentarily. This saves getting in and out of the car but prevents you from shifting to 4WD on the "fly" (while moving forward). On all wheel drive, the front hubs never disengage and the front driveshaft's turn all the time.Vehicles with part-time 4WD also have a "transfer case" that splits drive torque between the front and rear axles. On some vehicles, the vehicle must be stopped or going slower than 2 mph before the transfer case can be shifted from 2WD into 4WD. On others, the transfer case can be shifted while traveling as long as you are not exceeding 55 mph.On SUV's and similar vehicles, you can also select 4WD low range (4Low) or 4WD high range (4Hi). The low range is for creeping along at slow speeds while driving on rough off-road terrain. The high range is for driving at faster speeds on snow covered pavement or gravel or mud roads. Full-time four wheel drive, on the other hand, is just what the name implies. All four wheels are constantly driven by the engine to provide maximum traction. This type of setup is used on some performance cars to enhance handling traction. Most such vehicles have a "viscous coupling" in the drive train or transfer case that allows a certain amount of "give" in the drive torque between the front and rear wheels. This is necessary to compensate for the different speeds at which the front and rear wheels rotate when turning a tight corner. Four wheel drive does not necessary mean that all four wheels will provide constant drive traction. Unless a vehicle has limited slip differentials, its possible that either wheel on the front and/or rear axle may lose its grip and spin while its companion just sits there. Thats the way standard differentials work. Even so, with four-wheel drive, you will always have at least one front and one rear wheel turning at all times.