I am overhauling the front end on my '68 Camaro and had Harry's Steering Gear rebuilt my standard power steering gearbox. He converted it from 4.25 turns lock-to-lock to 3.33 turns lock-to-lock. With this modification, will I need to use a different pitman arm. My steering arms are part # 3902520/3902519. I purchased a TRW part #18769 pitman arm (which measures approx. 5.25 to 5.38 inches long center to center). Should I have bought the longer pitman that measures about 5.78" long?? Any help/advice/info would be greatly appreciated. Thanks!!

You have the shortest outer arms which helps a lot. Lock to lock doesn't really tell a lot about box ratio because there are different stops that can be used inside the box.
If you have the 12 to 1 ratio, you can use your short pitman and you will have pretty fast steering. It will be even faster with a longer pitman, the 5.75" long one.

I've got the long pitman arm part number on my page below in the steering section.

You should also ask for the box to be rebuilt with stiffer valving to give better feel like the later boxes.
David

I too am going to replace my power steering box w/ new one from 3rd gen camaro. I have 68. Do I need to replace pitman arm? Will the old one work?

Your old pitman will work if it's a power type.
But when/if you remove the pitma from the center link, use a tie rod puller, not a pickle fork. That will do less damage to the joint and seal on the pitman arm.
David

Thanks for the help. One more question. What is power type pitman? How do I identify it?

Been there done that. I went with 86 Z28 p/steering box. What a difference. graemlins/thumbsup.gif

Rando,

Yes, go with the longer pit arm 5.78 the number is TRW #18770 $58.69.

Ed,

Power pitman just means it only works on p/steering boxes.

You said above you have pow/steering now, so yes your pit arm will work but I wouldn't use it unless you know it's good. I also wouldn't use it if it doesn't measure 5.78 center to center. You can get a brand new one TRW #18770 for $58.69 at Advance auto. I would also replace the Idler arm TRW #18718 $30.98 unless it's not from 1968 and doesn't wobble.

I bought mine at my local Advance Auto store. So don't buy on line unless you have to.

Pit page
http://www.partsamerica.com/PartDetails.asp?SourceArea=&SourcePage=SEARCHRESULTS&MfrCode=TRW&MfrPartNumber=18770&PartType=69&PTSet=A

Idler page
http://www.partsamerica.com/PartDetails.asp?SourceArea=&SourcePage=SEARCHRESULTS&MfrCode=TRW&MfrPartNumber=18718&PartType=63&PTSet=A

[ 06-22-2004, 09:42 PM: Message edited by: RamJam ]

Thanks for the info. I too, bought my parts at Advance Auto. I will exchange my short pitman for the longer pitman.

The P/S pitman arm's hole is bigger then the non-P/S one's...

That's the only diff. that I know of outside of the different lengths that were used for both types..

pdq67

The Pitman arm and Idler arm must be of the same length to keep the Ackerman steering theory correct.

The frame, centerlink, Pitman arm, and idler arm form a parallelogram. When making a turn, the wheels travel in a different arc. This Ackerman steering theory keeps the wheels making the same arc whether a left turn or right turn.

A shorter/longer arm for either one will make for a mismatched arc between left & right turns.

Everett, David,

My '69 power steering knuckles\steering arms are part numbers 3954875 and 3954876 which measure 3.25". Short!
According to your site David: "This "short" outer arm -3954876 gives you the fastest ratio when used with the long pitman arm on the box." My pitman and idler are the 5.25" pieces. Short pitman!

MOOG\TRW part numbers for pitman:
Pitman, PS long, Moog# 6582 New production run, no grease fitting - Currently available at any auto parts store that sells Moog parts.

Pitman, PS long, TRW# 18770 Same as above. Probably a Moog part in a TRW box.

So if I switch to the longer pitman arm in order to increase to a faster ratio steering setup, I'm throwing the Ackerman angle off. What problems will I see with suspension wear, tire wear, ball joint wear? How detrimental will swapping to the longer pitman be? Everything in my current steering assembly is for power steering from the factory.

Gentleman, After rereading my post on Ackerman steering, I am wrong. The spindle arm length/angle, what the outer tie rod attaches, determines the Ackerman steering.

To determine the correct pieces to work with each other as a whole, one must "string" the front axle to the rear housing. For example, front wheels pointing straight ahead, loaded car (not on stands), run a string from the lower ball joint, grease fitting, to the center of the rear housing, right underneath where the two axles join together on the bottom of the housing. The outer tie rod joint, grease fitting, should be right in line with this string, not to either side of the string.

All else being equal, this angle of the spindle arm determines the arc the wheel will travel while in a turn. If one of these spindle arms is off from the string, the wheel it controls will be traveling in a different arc, hence, listen for the squeal in a turn or observe the rapid tire wear of one tire compared to the other side.

Now, with the above in mind, if the Pitman arm or idler arm is of different length than the other, the shorter arm'd wheel will again travel in a different arc. Same symptoms apply. Remember, the parallelogram created by the frame (attachments of the steering box & idler arm), Pitman arm, idler arm, and centerlink, must remain a parallelogram at all times, straight ahead or in a turn, for each tire to "track" correctly in a turn.

Make sense? I apologize in leading you all astray. If the alignment of the car is good, but, tire wear is accelerated for one tire, or a squeal is heard during a turn, it could be one these items is off.

Case in point, a friend had an extended cab truck front spindle replaced. After 6 months driving, one tire wore out. After many trips to repair shop and nothing found, I suggested the truck owner to have the shop check this Ackerman steering. Come to find out, upon repair, a standard cab spindle was installed rather than a spindle for an extended cab. Correct spindle installed, problem went away.

so, by your way of measuring, if a Camaro with all the "right" parts has proper ackerman settings, then my Nova with the same parts will be off due to the longer wheelbase? they used the same parts from the factory.
or, how about if you run different toe and camber settings- which would move stuff up and down and in and out a bit- say, street compared to a full race setup? or how about the guldstrand mod? how would that affect all this? i'd bet not enough to worry about, and most assuredly within "spec".

the First Gen Camaro has much better Ackerman correction than later vehicles because it has a rear steer linkage. Our 73 Camaro has less Ackerman than is "correct" our 85 Z/28 had less too.
Racers at one time used Anti-Ackerman to "correct" front tire angles to a more favorable angle at high slip angles but setups are swinging back to more of a true Ackerman layout these days.

One of the things I'd like to do some time is measure Ackerman changes due to different pitman arm and idler arm lengths. The length of pitman affects the F/R position of the center link, the center link location affects Ackerman but not a whole lot if you are talking about 3/4" differences F/R.

GM used either a long or short pitman arm depending on steering ratio ordered from 67-69.
67 idler arms are longer than 68/69
Replacement Moog/TRW 68/69 idler arms are aprox 3/8" shorter than originals, so it sort of splits the difference of pitman arm lengths.

Make a U turn in the dirt and go back and look at your tire tracks, see which one dug up the dirt! smile.gif

If you have a fast ratio box with shortest outer arms but short pitman, your ratio is pretty fast, the longer pitman will speed it up a little, maybe reduce lock to lock by a quarter turn or so.
David

Good info!! Does anyone know the TRW part number for the correct idler arm to use with a long pitman arm (TRW pn 18770)? I now have a TRW pn 18718 idler arm and the pn 18770 pitman arm was ordered today. Thanks for all info!

I agree with what Everett is saying the thing is like David said it must not make much difference on stock camaro's because there is no different length Idler arms to buy.

To answer rando's question. If you are talking stock you can only buy 1 type for each year and 68-69 are same part#

Myself I'm using the 68-69 Idler on my 67 because I didn't want to pay $120.00 for a 67 when I could get a 68-69 for $30.00

David, me and some others already had this discussion last year that's why I thought it was safe to use the 68-69.

This link should shed more light on this.
http://www.camaros.net/cgi-bin/forum/ultimatebb.cgi?ubb=get_topic;f=7;t=005633

Go here type Idler arm hit search button.
http://www.parts123.com/PartFrame.asp?ZTM=cadegghb&GHOME=www.classicindustries.com&TITLE=Classic_Industries

Thanks Everett, that makes perfect sense. I'd be "stringing" mine for the geometry this weekend, but it's not aligned yet.

As far as alignment adjustments and things like the Guld. mod affecting the Ackerman, I guess I'll find out. It sounds like having the Ackerman off is not something terribly detrimental that one should worry too much about.

I still don't know the ratio of my box but I guarentee it isn't a faster ratio unit. And if a longer pitman would only change the lock-to-lock a quarter of a turn when using a fast ratio box, I'd assume that would be true for the other ratio's offered also and it wouldn't make much sense for me to change mine.

Thanks all!

Joe,
If you have a slower ratio box, I'd recommend the longer pitman.

If you have a 12 to 1 box, short outer arms and allready have the short PS pitman, I think the difference is maybe a quarter to a third turn more. There might be less of an incentive/difference to spring for the longer pitman arm.

The 12 to 1 box with long pitman and shortest outer arms comes to 2.25 turns lock to lock if I remember right. So a short pitman would be something like 2.5 to 2.75 turns, but a slower ratio box would be more like 3 to 3.5 turns and that's getting pretty slow.

If you have the long outer arms the ratio get's REALLY slow, mine used to be four turns lock to lock before I got the shorter outer arms.
David

With short steering arms, long pitman, and fast ratio box it does not take much wheel movement to get the car to steer!

If I had a choice between a really good stock pitman arm vs. the TRW/Moog replacement I'd stick with the stock part. The replacements use a nylon type sleeve for a wear surface instead of the metalic materials used in the stock versions. This causes more deflection in the joint vs. the stock part. For street cruisers it's no problem but if you really push the car it would be nice to have a more rigid part.

Man... now ya got me looking for a factory original LONG pitman arm! I plan on pushing this thing for all it's worth.... if I didn't, I would have kept the GM suspension.
graemlins/thumbsup.gif

Joe,
If you can't find a long pitman, get a 12.7 to 1 box with stiff valving and use your short pitman if it's an original GM PS pitman and is in good shape.

My original 67 PS long pitman is still in great shape after 150K miles and lots of autocrossing with 10" wide ft rims!
I did grease it often with high quality grease.
David

OK, so if I understand this right, it doesn't matter if you have a short or long pitman in a TRW or MOOG-neither will be manufactured like the original GM parts? In otherwords, the GM/original parts will last longer and take more punishment? Could someone reply if this is correct? Thanks!!