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TR4 Wiper motor gears


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Hi All

I seem to be back in the fold having bought another TR4!!

As the windscreen wipers only go halfway across the screen I suspect it has the wrong gears in the motor - the thing is what is the correct one and are spares available from anyone?

Regards

John

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It's possible that the wrong gear is fitted but more likely that you have wear in the rack and/or wheelboxes. It may also be that the wheelbox clamps are loose allowing the rack tube to move around. The standard gear wheel should be marked 120 degrees.

Edited by peejay4A
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It's possible that the wrong gear is fitted but more likely that you have wear in the rack and/or wheelboxes. It may also be that the wheelbox clamps are loose allowing the rack tube to move around. The standard gear wheel should be marked 120 degrees.

Many Thanks

Regards

John

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I make these gear wheels by moving the crank-pins about.

A movement of 0.005in produces a 1 degree change in sweep.

 

Another way to look at this is, quite small amount of wear in the wire-rack, wheel-head gears, the rack-nipple, the crank-arm and the crank-pin can all add up to a lot of slop at the blade tip.

 

Take the cover-plate off the motor, so you can see the wire-rack and nipple. Move the blades and see how far they go without the crank-arm moving. The fourth screw will have you swearing!

 

120 degree wheels are hard to find and actually a bit too much sweep really. a TR6 uses 115 degree.

 

Often 100 degree degree wheel from Morris Minors get fitted. But more commonly sweep seems to be too big due to wear.

 

Probably the first thing, the easiest thing is a new wire-rack. Try to get NOS and simply cut to length with a grinder. Don't be afraid to pull the wire-rack out. They slide back in quite easily with a bit of wiggling.

 

Replacing the wheel-heads is AWFUL. Sometime you can find a section that is unworn. Remember only about one third of the teeth are in use.

 

Ask if you want some photos. I have loads.

Edited by AlanT
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John Remove the wiper arms and mark a dot with Tippex on the top side of the knurling then pull the rack cable out and turn the wheel-box stubs 180 and refit the cable so when in place your marks are opposite where they were this will allow you to use the unworn sections of the drive cogs.

Stuart.

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Hi All

I seem to be back in the fold having bought another TR4!!

As the windscreen wipers only go halfway across the screen I suspect it has the wrong gears in the motor - the thing is what is the correct one and are spares available from anyone?

Regards

John

John, What shape is the wiper motor body - square or round? Square is correct original . Round is TR6/Defender

What shape are the nuts on the wheel boxes 6 or 8 sided - This will tell which wheel boxes you have fitted are there are two types with different amounts of teeth. 6 sided is correct for orig TR4 with square motor. 8 sided is correct for TR6 which has the round body wiper motor.

 

Cheers

Peter W

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  • 1 month later...

Hi All

Apologies for the long delay between posts!

I have the correct motor (square) and having taken off the cover expected to see the wrong gear wheel but no I have the 120 deg one.

The wheel boxes are correct I am told by TR enterprises they do have 6 flats on the nuts.

To my mind this only leaves the rack - as the wipers are only going halfway across the screen it seems unlikely to be wear/slop.

Moss list the same part nos for the rack for TR4 - 6 I thought they were different.

Any advice gratefully received.

Regards

John

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http://www.ebay.co.uk/itm/AUSTIN-MORRIS-MG-BL-LUCAS-WIPER-DRIVE-CABLE-RACK-LUCAS-743251-BL-RTC202-/282268605015?hash=item41b8851a57:g:RC4AAOSwYGFUy4B0

 

They are mostly the same except for length. Cut off to suit with angle grinder.

 

I always look for NOS.

 

How much slop at the end of the blade?

 

Remember 1 degree of slop for every 0.005in wear.

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http://www.ebay.co.uk/itm/AUSTIN-MORRIS-MG-BL-LUCAS-WIPER-DRIVE-CABLE-RACK-LUCAS-743251-BL-RTC202-/282268605015?hash=item41b8851a57:g:RC4AAOSwYGFUy4B0

 

They are mostly the same except for length. Cut off to suit with angle grinder.

 

I always look for NOS.

 

How much slop at the end of the blade?

 

Remember 1 degree of slop for every 0.005in wear.

Hi Alan

I have got 2.5ins of slop at the wiper blade thanks for the link I will buy it as soon as I can get broadband to work!!

Regards

John

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When fitting the new rack, try to find a bit of the wheel-head gear with less wear. Only about one third gets used.

 

Ensure the outer rack-tubes are all tight.

 

This may help:

http://www.ebay.co.uk/gds/What-Could-Possibly-GO-WRONG-/10000000211157905/g.html

 

and this:

 

http://www.ebay.co.uk/gds/Fitting-Instructions-/10000000208662078/g.html

Edited by AlanT
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It's a good tip, but don't be too hopeful about recovering efficiency by turning/rotating parts. After 50 years or so it is unlikely you will be the first to do this.

My wipers were so knackered I upgraded to TR6 wheel boxes and rack. The boxes are easier to fit and better designed and made, [the 4 boxes are the same as the side screen cars with their much smaller screen]. Easier to fit is true but minor as getting access is a right pig of work. I could not detect any difference between the '4 and '6 racks.

Mike

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The chance of finding NOS original Lucas wheel boxes is now pretty remote and if some are found they will likely command a king's ransom - here's a tip for anyone fitting replacement pattern type wheel boxes, which could save a lot of grief. AMHIK! This is a time consuming and fiddly job, definitely not one you want to repeat in short order, Before fitting to the car place the body of the new wheel box in a vice and insert the rack. Lock the wiper spindle in some way to prevent it turning and apply a high force to one end of the rack, this will simulate the high torque load should the wipers be operated on a dryish screen. This check is to ensure that under these conditions the rack and pinion remain engaged. On some pattern parts dimensional control on the manufacturing process is inadequate and it is possible for the rack to simply ride over the pinion under high loads. If this happens on test all that is needed is to dismantle the wheel box and carefully reshape the cover plate so that it holds the rack in close contact with the pinion but without it binding.

 

Tim.

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Yes it's the rack-wires that are usually about NOS.

 

The trouble with wheel-boxes is that there is a huge variety. Angle and length were both adjusted to suit body design.

 

Although I have successfully "rehomed" a few it's much more difficult than motors, which are pretty much all the same.

 

They are stamped with part-numbers though and the gears all pretty much the same.

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  • 2 weeks later...

Yes it's the rack-wires that are usually about NOS.

 

The trouble with wheel-boxes is that there is a huge variety. Angle and length were both adjusted to suit body design.

 

Although I have successfully "rehomed" a few it's much more difficult than motors, which are pretty much all the same.

 

They are stamped with part-numbers though and the gears all pretty much the same.

Hi Alan

The saga continues!

I obtained a NOS rack although it took forever to arrive installed it and it took up all the slack in the wheelboxes.

Great then I discovered I still had slop at the wipers caused by (I discovered) considerable wear in the hinges of the wiper arms.

Obtained some new wiper arms and they still didn't go across the screen fully ARGHHHHHHHHHHH.

Then decided to recheck the gear wheel again and it was 120deg but it looked as though the teeth were worn down compared to the spare obtained on ebay.Oh well change them over and see if there was any difference and lo and behold they now work!!

Thank you for everyone's input.

Regards

John

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