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MG TD TF 1500 - Front end alignment on TD ?
Good day all. Sorry to bother you on Sunday but………
After returning from 2,000 mile trip last year, I noticed tire wear on front right tire with some wear on left tire. Read threads for checking alignment in archives, made jig to check alignment per David D. With “The Original British Car Day” near Adamstown , Md 21710 approaching; I wanted to drive the TD there. So yesterday I checked the front end alignment, test drove the TD and returned to garage checked the alignment again found it once again off. A check of the tie rods seemed good. But I am getting some movement and noise in the steering rack. Is there some way to take the play/movement out of the steering rack. Are they re-buildable, and if so who dose the rebuilds. Can you use racks out of MGA’s ? Thanks in advance, John
|John, I don't believe you can mount an A rack on your TD. I also don't know who rebuilds them, although John Twist is still offering bench services. But they can be benched serviced at home. At the top of the rack on the pinion side (where the steering shaft comes out) is a cover that looks like a giant acorn nut. Under it is a spring and a damper pad that preloads the pinion shaft to the rack. You place shims in there to get the correct preload.|
The rebuilding process on a rack, assuming the rack and pinion aren't too worn is to take it off the car (which is just barely possible as shown in the Shop Manual and you have to do whether you do it yourself or send it off) and disassemble it, inspecting all the parts. Points of concern is the free play in the ball joints that are hidden inside the rubber steering boots and the wear on the teeth, pinion gear and the surface the damper pad rides upon. You uncrimp the housing covers and gain access to the ball seat. Remove some material from the ball housing face to take out the play. Schach's book has a nice article on this.
To withdraw the pinion shaft, you need to remove the flange at the steering column end of it. A 15/16 socket with the edges filed down makes a nice standin for a 1/2W socket. You can then use a small puller to remove the flange, then drop it through the access plate provided at the bottom.
Make sure you have the proper thrust washers in place and you are all set except for one thing.
I'm pretty convinced that the reason the makers specified gear oil for the stearing rack is that they believed that the rubber boots would act like plungers, distributing oil to the rack and inner ball joints every time the wheel was turned and the boots excersised. Grease is just going to lump up and may or may not flush through the rack and the ball joints. It is a bear sometimes to get the appropriate 90 W gear oil, it takes about 13 oz. but it is worth the effort. On the other hand, it is straightforward to put the oil in from the top before installing the damper and spring, or even pouring it in vertically while on the bench, and that is what I would recommend. After you add the gear oil, keep the pinion shaft up. Even with a new felt seal, overfilling the rack, or tipping it over can spill the lube.
Finally, you may as well replace your outer ball joints as well. The screw thread ends of these may be too long and need to be cut off to give you the amount of thread needed to adjust your alignment again.
There are some pictures of the rack on my website, under steering.
Hope this helps,
I meant it is a bear to get the 90w gear oil into the rack! The oil you can get at any autoparts store. A lot of folks use a bulk loading gun with a fitting to match the zerk on the front of the rack. But once filled, unless you tear a boot (like I did last week) you will never need to refill the rack, and you will still have to know it is empty to refill it with 13.8 oz.
|Here is my input on adjusting front axle toe on MGs or most other cars.|
Checking/Setting Front Axle Toe-in
Toe-in can be easily checked on any automobile and with a little effort corrected to the required 1-mm plus or minus 1-mm or 1/32nd plus or minus 1/32nd. To complete the task you will need masking tape, a tape measure, preferably metric, a pen and an able helper.
You start by driving the car forward and backward on near level ground for at least 5 tire revolutions in each direction while fiddling with the steering wheel to ensure that the wheels are pointed straight ahead. The last step in this part of the process is to back the car to its starting point and stop the engine. Now, take your hands off of the steering wheel and have your helper push the car forward for about two tire revolutions. If the car tends to roll use the hand brake only to stop and hold the car in place.
The measurement phase consists of placing a piece of masking tape, about 2-3 inches long, at the rear of each tire. The tape should be place vertically near the center of the tire tread. Next, using your pen, place a small horizontal tick mark at the inner edge of each piece of tape. The tick marks should be as high off the ground as possible while still being able to have a clear line of sight from tick mark to tick mark. With the aid of your assistant, CAREFULLY measure the distance between the edges of the each piece of masking tape at their respective tick mark locations. Be sure that the tape measure does not touch any part of the underside of the car. Now, push the car forward, without touching the steering wheel, while carefully observing the masking tape. Stop the car, using the hand brake only, when the tick marks are as high off the ground as possible while having a clear line of sight between the tick marks. Remeasure the distance between the tape edges at their respective tick marks. Now, subtract the two measurements to obtain the toe value. If the distance measured at the rear of the tire is greater than the front, your front axle will be toed-in. It is easier to get an accurate measurement if you use the 100-mm or the 4-inch as the starting point because we are not interested in the actual distance but rather the difference between the front and rear.
This method of checking front axle toe is very accurate because you are measuring between the same two points on each tire while the points are at both the front and rear positions. Tire and wheel run out and tread pattern irregularities are accounted for.
If you find the your toe is out of specification you can make proper adjustments. Start by changing the front distance by one half of the error. Then push the car forward (never backwards) and remeasure the rear distance. Make a small toe adjustment if necessary, and repeat the entire process until you have reached the desired toe-in value. After you think that the toe is correct take the car for a short drive and repeat the measurement process.
Although time consuming, I can assure you that this toe measurement technique is at least as accurate, and more reliable than alignment shops offer. This is a direct measurement that does not rely on equipment calibration to ensure accuracy. If you want caster and camber measured/corrected or a four-wheel alignment on a modern car you must go to an alignment shop. Use the above method to check their work. You will be surprised! Have you ever noticed tire wear after 6-months of driving after an alignment, taken the car back and told that you must of hit a curb or a chuckhole. Sure
I've done just as you have suggested, but the problem is in the streeing rack with up and down movement in the rack. About 1/4 inch play. John
|John - it sounds as if your steering rack damper assembly is worn and the preload is out of spec as a result. That is actually an easy repair (if the top surface of the rack is in fair condition).|
That assembly consists of the cap, spring, plunger, and shims.
I would remove the assembly and then let us know what you find. Your plunger is most likely worn. Newe plungers are available. You can then set the damping as detailed in the shop manual in section J.7. - Do you have the factory manual?
You may also have loose inner ball joint caps - this is more involved.
Let us know what you find under the damper cap.
|J. W. Delk|
I have the WSM and after I go to the OBCD this Sunday I'll check this out. I put 90 W gear oil in it yesterday and that took out most of the play/ slack out. Don't ask me how, because I don't know. I think that the gear oil is between the hardened up grease and the steering rack arms? John
This thread was discussed between 31/05/2009 and 05/06/2009
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