Driveline & ujoint angles
When installing a non-stock transmission such as a TKO into a classic Chevy, we occasionally receive questions about driveline & ujoint angles. Some of the questions that come up are: why do I have to worry about angles, aren’t ujoints supposed to solve angle problems? Or: I have a vibration, is it being caused by my driveshaft? The following rules of thumb and the attached link should help you understand ujoints and their limits and help you put your driveline together without problems.
Both the transmission output shaft (which includes the entire crank centerline of the engine) and rear end pinion should both be on the same angle (parallel, or as close as possible). The ujoints should have an EQUAL (within 1*) AND OPPOSITE (to each other) ANGLE of no more than 3.5 degrees. This is a perfect world setting, but we all know that's not always achievable. The closer you can get to these specifications the longer your ujoints will last. The farther from these settings you go, the lifespan of the ujoints is reduced and the possibility of vibration associated with them increases. This does not mean that you will have a vibration that you can feel if you are not right on these specs. The goal should be to get as close as you can. Ujoints MUST have at least a ½ degree angle to operate. A ujoint that is zero angled will not last very long. There are a lot of modified cars on the road with less than desirable ujoint angles and they run with no noticeable vibration but their lifespan will be shortened. Another thing to consider is spring wrap which is a very important thing to consider when diagnosing a vibration problem. There have been a lot of people who have incorrectly diagnosed a driveshaft vibration and have blamed the driveshaft when it isn't the problem at all. When accelerating and decelerating the pinion angle changes. When accelerating the pinion goes up, when decelerating the pinion goes down. This changes the ujoint angle drastically, especially at the rear. If your springs are weak or if you have a lot of horsepower with good traction, this can be a real problem because as the angle increases beyond acceptable limits the vibration gets worse. Try to get your angles as close as you can then worry about stabilizing the rear end if it becomes an issue. Have a look at the link here. It should help you further. Thanks to the Driveline Doctors for this.
One other thing to consider is driveshaft RPM and length. The faster a driveshaft spins and the longer it is there is a greater possibility of the “skipping rope effect” to occur. This is very dangerous as the drive shaft will want to fold in half and we don’t need to talk about why this is not a good thing. Make sure you talk to your supplier about your intentions with your car. The supplier of your drive shaft will work with you to get the correct length and material thickness for your application.
Clutch Fork Alignment & Throw Bearing Adjustment
If you are using a stock GM bellhousing you will simply need to use a stock length throw out bearing, stock clutch fork, and stock ball stud. No clutch fork adjustments are required.
If you are using a scattershield you will need to make sure your clutch fork and TO bearing are properly adjusted. Using an adjustable TO bearing and/or an adjustable ball stud will help you achieve the clutch fork angle that is required. Click on this link to see an illustration and detailed instructions: http://www.classicchevy5speed.com/fi...ring_instr.pdf
Pilot Bearing Removal
Pilot bearing/bushing removal can be accomplished in different ways. Packing grease behind the bearing to press it out is one method but here is a tool we found that makes the job clean and easy. Visit www.springertool.com
to purchase this specialty tool. Click here for a picture: http://www.springertool.com/files/3sizes_1.jpg
Before installing your new Tremec TKO transmission, it is important to make sure that your bellhousing or scattershield is properly aligned with the centerline of the crankshaft. The alignment process is called “dial indicating”. If using a stock GM bellhousing or a Lakewood scattershield, dial indicating is necessary before installing your transmission. If you are using a McLeod scattershield or a CC5S reproduction aluminum bellhousing and your motor has not been line bored, checking alignment is not necessary as these scattershields are built to within .005" of the crank centerline (the max required run out for installing a TKO)***. A bellhousing that is not centered with the crank can result in poor shifting, clutch engagement problems, worn pilot bearing, as well as accelerated wear on the transmission itself.
*** If you choose to check alignment a McLeod scattershield, do so without the silver register ring installed in the register hole – checking alignment with this ring in place will give you a false reading.
Unfortunately checking the alignment can be a tedious task, especially if the engine is still in the car. To check for proper alignment, you will need a dial indicator, some basic tools, and a bit of patience.
Checking bellhousing alignment
1. Making sure that dowel pins are clean and free from dirt and/or paint, securely mount bellhousing to the engine block, and torque all bellhousing-to-engine bolts to specification. If you are using a scattershield, make sure the block plate is installed. Make sure your stock dowel pins protrude out far enough to let the scatter shield and block plate fit on the flat part of the dowel and not the tapered part. If the scattershield is resting on the tapered part this can cause inaccurate measurements. It may be necessary to tap the stock dowels out far enough to allow this. Moroso makes longer straight dowels for this purpose.
2. Install dial indicator base on the flywheel and adjust plunger to contact the inside edge of the register bore of the bellhousing. If you need to create space for the dial indicator base to sit flat on the flywheel, remove two of the flywheel bolts that are directly across from one another.
3. With the dial indicator mounted correctly, rotate the crank 360* and note the indicator readings. Using an inspection mirror to read the gauge as it rotates is helpful. Mark your readings at the 12:00, 3:00, 6:00, and 9:00 positions. This will give you an indication of which direction you need to move the housing - if necessary. Make sure to double check your readings. The total travel of the needle, divided by two, equals your reading – this reading is the amount of misalignment between the crank centerline and the bellhousing bore. Tremec specifies a maximum misalignment, or “runout” of 0.005". If you have more than .005” runout you will need to correct this by using offset dowel pins. If your reading is 0.005” or less, your bellhousing is within tolerance and you are finished with this process. If you have between 0.005” – 0.040” misalignment, you can correct it by using the correct offset dowel pins (proceed to step #4). If your misalignment is greater than 0.040” you have either measured incorrectly or there is a problem with your bellhousing and it will likely need to be replaced.
Bellhousing alignment procedures
1. To correct misalignment, you will need to use offset dowel pins. We have found an excellent set of offset dowel pins from RobbMc Performance Products (www.robbmcperformance.com)
. The job is much easier with these dowel pins.
2. Start with the indicator at the 12 o’clock position and turn the engine 360 degrees (one full turn). Mark the locations where the reading is highest and lowest. These readings may cover a large area but will help determine which direction to move the housing to correct misalignment. Now put the indicator in the center of the area of the LOWEST reading and ZERO the indicator (for example, if the lowest reading was between 7 and 9 o’clock you would put the indicator at 8:00. Now rotate the engine until you get the highest plus or positive reading – in this example it should be somewhere near 2:00. If the reading is .014” you would need to move the housing towards 2:00 by .007”. If it were .020” you would move it .010”. After the initial learning curve you will understand how this process works. Remember that all readings are divided by two. This can be a frustrating process. Have some patience and use a notepad to record your measurements, not the face of the bell housing as it will get full of measurements quickly. After your dowel pins are in you can turn them as needed to get the required alignment.
To install offset dowel pins, first remove the stock dowel pins by driving them through from the back with a brass drift or by using gripper pliers – sometimes this can difficult to do, especially with the engine still installed in the car. Another way to remove the dowels is to remove stock dowels with a slide hammer. To do this try using a 1/4"-28 attachment on the slide hammer. Next, drill the dowels and tap them to accept the 1/4"-28 attachment and then use the slide hammer accordingly.
Properly clean engine block dowel pin holes and lightly coat with lubricant.
4. Lubricate dowel pins and install them into engine block. The slot of the dowel pins DOES NOT indicate the direction of maximum offset. You must find the high spot on the dowel with the dial indicator and mark it so the dowels can be installed parallel to one another.
5. Install bellhousing and torque bolts to specification. Re-mount the dial indicator and recheck runout by repeating step #3. Small corrections can be made by loosening the bellhousing bolts and turning the dowels with a screwdriver to bring the bellhousing within limits.