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620 Rack and Pinion


]2eDeYe

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Off the top of my head, stock pivot to pivot was something like 22.75" I took out 3 3/16th. I got my inspiration from Aussie Toyota forums.

 

Really what I did was this, took the distance from ball joint to tie rod pivot (perpendicular to direction of travel). Multiple by 2. Remove this distance from your lca pivot to pivot, this is pretty much your target pivot to pivot of the rack. YMMV.

 

Also rack travel, you can increase it by shortening the housing more. But you run into a problem with pinion clearance.

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The Triumph TR6 and MGB both use front mounted steering racks.  I no longer own a TR6, but I can measure the MGB's travel.  Tie rod size is something that can be altered if necessary, as can rack mounts - 4 "through" bolts in each of these cases.    If I recall the MGB has 3 1/2 turns lock to lock.  Tires are a bit shorter than the 620, but has a very tight turning radius so I have to assume the distance traveled will be similar.  The rack has very long gators/boots that go from full compression to nearly full extension.  

 

My Willys ratrod uses a 2001 Malibu rack.  Its mounted behind the front wheels, and I simply made custom steering arms to utilize it.  That also allowed me to alleviate bump steer inherent to the Planar front end.  

 

My 620 always had a non-integrated steering box.  Was this addition made in later production years?  I now run a Speedway collapsible column and quick release steering wheel for easier entry/exit.  That was a simple afternoon task.  I don't see how a R&P would likely take more than a day to fit, but I don't see a benefit.  The 620 has no real steering issues and all the tie rods are available at a cost significantly lower than an R&P.  

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Wouldn't a Smart Car R&P be designed for a very light car? It isn't power assist? Would this then not be the correct ratio for a 620? The 620 steering ratio is 19 to one. At 19 to i it's barely ok for a stock 620. With 10.5 X 31s it was a wrestling match to park.

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Wouldn't a Smart Car R&P be designed for a very light car? It isn't power assist? Would this then not be the correct ratio for a 620? The 620 steering ratio is 19 to one. At 19 to i it's barely ok for a stock 620. With 10.5 X 31s it was a wrestling match to park.

The ratio is info I'm hoping to get next week. Otherwise, yes Mike, you are totally correct. In my head, the only guys who might want r&p were the 2wd guys. I think this rack will likely be fine in that case. However, with guys like you and redeye in the 4x4, I would not consider the smart to be a good option.

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I looked into this a bit when I had my 620. I had(might still) had a catalog from one of the major rack and pinion rebuilder that list all the rack dimensions for most of the power racks. I could not find anything that was anywhere near close enough to fit the dimensions of a 620 in a front steer power rack configuration.

Rear steer I seem to recall something close to narrow enough, but you can't just swap spindles left/right to get rear steer. The Ackerman angle built into the steering arms would be all wrong and should cause handling issues.

The book I had did't list much for manual racks( and I wasn't interested in that option). That book was also just old enough that the smart car would not be in it.

 

Good luck in this research. I think it could be a good addition for the 620. I was never very fond of the 19:1 factory box or the solid steering column.

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You can always do 2 things: use electric power steering with a manual rack, narrow a rack by further threading the inner tie rod ends.    If the truck is well balanced, power steering will be unnecessary in most cases.  Of greater importance is the rack mounting system, and the steering shaft position.   If the steering shaft points into the frame or directly into your exhaust pipe, you have bigger problems than if its too long.  

There shouldn't be much concern with what car it was designed for - they don't make racks weaker for lighter cars.  If installed properly, all the forces will be applied in a straight line directly through the rack's length.  Steering u-joints may be lighter for lighter cars, but you will be using aftermarket joints anyway.  Personally, I was allowed to go into my local Napa store and dig through boxes on the shelf until I found a rack that fit my application, then I got a 10% "hotrodders" discount because they thought the project was cool.  

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To clarify a few things. 

 

I would not use rack and pinion in a solid axle 4x4. It would be difficult to get the shaft geometry right and allow the suspension to move through its cycle. Not to mention oversized tires would be pushing the limits of most racks that are available in the size needed. 
 

 

That smart car is about 1000lbs which is 1650 lighter than a 620 kingcab. Not sure if that would be a deal killer for the smart car rack, but it would be interesting to see what loads the smart car rack is rated for. 

 

 

Not sure I want to put a specific motor into the equation, Depending on the rack it might still work with a front or rear sump configuration depending on the motor used. Pans can be modified fairly easily anyways. 

 

 

All good info dumping into this thread. :cool: 

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I would not use rack and pinion in a solid axle 4x4. It would be difficult to get the shaft geometry right and allow the suspension to move through its cycle. Not to mention oversized tires would be pushing the limits of most racks that are available in the size needed. 

 I totally agree!!!  4x4s need very heavy steering links that can stand a little physical abuse.  The alloy center section of a rack won't take a rock hit like a drag link.  Broken thumbs and front tires pointing in opposite directions will ruin your day.  

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I have a custom manual rack.  I suppose you could add one of those piston assist things on there.  The pivot points have to be a shade over 16 inches, depending on how high you mount the rack.  The higher the rack, the wider the pivot points need to be.  Also keep in mind the location of the pinion, the further to the outside the better.  I had to add another u-joint to keep it from binding.   Steering u-joints are only good to something like 30 degrees.

 

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Orangie, you may want to go to a double u-joint on the upper.  Even that angle looks like its going to bind significantly.  Is that rack quite a bit closer to centerline than the original steering?  The closer you can get the tie rods to being straight (in line with each other) and level, the less issues you'll have with bump steer and bad ackerman angles.  

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I didn't mention, I have an SR20DET that had custom motor mounts.  I don't know how much clearance you will have with the stock motor between the rack and the oil pan.  This was a hard way to do things.  The advantage of a rack and pinion is a more precise feel of the steering with fewer parts.  If power steering is really all you're looking for, it's easier to get a later model frame where the steering box mounts on the outside of the frame.  You would have to ask around, but I believe the body just about drops right on.

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fyi, that wasn't the final version.  That's the basic idea.  There was some more refinement to take out the binding, but it does move without binding.  You can feel a very light bind by turning  the steering without the steering wheel, but once the steering wheel is mounted it feels good.  The car hasn't hit the road yet so I can't really comment about ackerman or bump steering.  Ackerman will probably be what it is and no adjustment, but for bump steer, it is possible to shim the rack up and down as well as the outer tie rod ends. 

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I'll go look.  It would be tough to take one now without ripping all the turbo stuff out of the way.  BTW, the turbo stuff makes it a nightmare to work on.  Stuff is routed around the steering shaft.  I forgot to mention I also have a shorty Ididit steering column and that allows me to use "D" shafts so linking everything up is simple.

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That was a good start, but no one actually answered with lengths.

 

But steering rack was 22:1 or 21:1 depending on electric vs manual.

 

Thanks for that link

 

I'm going to try calling one of the Smart Car Service Centers in California. See if one of the technicians will give me a few minutes and just pull a couple of measurements. Maybe I can do that Monday or Tuesday see what they say.

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