Borgeson and pitman arm problem

[denpo]

While in the process of installing a borgeson steering upgrade in my '76 I'm running into a problem : the pitman arm doesn't fit in more than halfway into the steering box shaft, we tried with a press but we stopped worried we could break something. Is there a particular method (heating?) or do I need to enlarge the hole with a file?

 

[BBShark]

Does Borgenson re-cut the splines on the Jeep box for the Corvette arm? If so, the fit problem is probably with the box not the arm. I wouldn't try to file the splines on the arm or the gear. Chances of maintaining the kind of fit you need on that is pretty low. Sounds like you need to contact Borgenson.

 

[denpo]

thanks, also checked my a mecanist buddy, pitman arm is supposed to fit in without so much force, just sent an email to borgeson.

 

[denpo]

Got a reponse from Borgeson : since the nut goes on most of the way it's fine.
So looks like I'm fine, can't way to reassemble all this once again, for good this time.

 

[mrvette]

Got a reponse from Borgeson : since the nut goes on most of the way it's fine.
So looks like I'm fine, can't way to reassemble all this once again, for good this time.

I assume you know from instructions or yourself, how to assemble it...

I would put the pitman in a vice, then tap that nut down with a impact and some locktite red....

:gurney:

 

[BBShark]

Got a reponse from Borgeson : since the nut goes on most of the way it's fine.
So looks like I'm fine, can't way to reassemble all this once again, for good this time.

That's not right. You want at least 80% engagement on the splines and, the C3 pitman is already undersized (as far as spline engagement length) for a modern gear with an integral servo. The stock box is unable to supply the kind of torque that a box with an integral servo can. So you are increasing the torque and reducing spline engagement. Not good.

 

[SmokinBBC]

Got a reponse from Borgeson : since the nut goes on most of the way it's fine.
So looks like I'm fine, can't way to reassemble all this once again, for good this time.

That's not right. You want at least 80% engagement on the splines and, the C3 pitman is already undersized (as far as spline engagement length) for a modern gear with an integral servo. The stock box is unable to supply the kind of torque that a box with an integral servo can. So you are increasing the torque and reducing spline engagement. Not good.

Wouldn't the geometry of the steering linkage be off as well?

 

[JIML82]

With an integral power gear the power assist is coming from inside the steering gear housing, above the pitman arm connection. So a pitman arm connection actually sees full roadwheel loadings as you steer the car.

With the old, obsolete, Corvette linkage booster power assist system, the assist is coming through the hydraulic cylinder which is attached to the relay rod. So the assist is coming downstream from pitman arm to gear connection. So the linkage booster system puts less stress on the steering gear and the pitman arm connection than the modern integral power gear system.

Now this isn't to say that you can skimp on steering connections just because you have a linkage booster system. However, I would think that if you torque the pitman nut to 140 ft-lbs of torque and at least one full thread from the sector shaft is sticking out through the nut, you should be safe.

Jim

 

[denpo]

Now this isn't to say that you can skimp on steering connections just because you have a linkage booster system. However, I would think that if you torque the pitman nut to 140 ft-lbs of torque and at least one full thread from the sector shaft is sticking out through the nut, you should be safe.

Jim

This is exactly what I ended up with, plus added some that blue nut blocker stuff, to be sure. Feeling safer now.

 

[BBShark]

Now this isn't to say that you can skimp on steering connections just because you have a linkage booster system. However, I would think that if you torque the pitman nut to 140 ft-lbs of torque and at least one full thread from the sector shaft is sticking out through the nut, you should be safe.

Jim

The original poster does not have a linkage booster system. He has an integral servo.

 

[VetteV8]

I have a request here:
As I also consider to replace the original steeringbox with the Jeep box, I would like to re-machine the Jeep shaft to the original Corvette shaft dimensions, just like Borgeson does.
For now I would like to have as precise dimensions as possible for the spline end, so the max and the min. diameter of the spines, and
the number of splines, and any 'blind' splines on that shaft.

I have a milling machine, but would need to buy an dividing unit, hence the need for the number of splines.

To those who have replaced the box I would ask to get your vernier out, and count the splines for me
Many thanks,
Cor

 

[BBShark]

Using the stock Corvete pitman arm is a mistake. It was never designed to carry the torque that an integral servo steering gear is able to generate. The spline engagement length on an integral servo gear is almost double the Corvette length. This is a good explanation:


JIML82 "With an integral power gear the power assist is coming from inside the steering gear housing, above the pitman arm connection. So a pitman arm connection actually sees full roadwheel loadings as you steer the car.

With the old, obsolete, Corvette linkage booster power assist system, the assist is coming through the hydraulic cylinder which is attached to the relay rod. So the assist is coming downstream from pitman arm to gear connection. So the linkage booster system puts less stress on the steering gear and the pitman arm connection than the modern integral power gear system."

 

[VetteV8]

I appreciate your response, and fully understand the reasoning why the load on the pitman arm on a steering gear with integral power is much higher than with the stock setup.

However there is no reason, I feel, why it should be not strong enough: if you are a strong man, all the power in a manual gear set-up, is indeed only going through the original pitman arm, so the load is the same, as there is no external power-assist.

Secondly, I believe that Borgeson, who puts complete modification kits on the market, modifies the Jeep steeringgear in order to be able to use the original Corvette pitman arm. If that lever is not strong enough, then would they never run into liability issues?

Thirdly, a practical point for me: I cannot hope to be able to lay my hands on a Chevelle pitman arm, as I happen to be in Europe, and Chevelles are not available anywhere [on junk yards at least, only in imported show vehicles]
Used Grand Cherokee gears are also not widely available here; just recently, the correct type was offered for sale for € 250 = $ 335
If I could get hold of a Chevelle arm, that would be great; as I am planning to get a number of parts from the USA and consolidate that into one surface shipment.
Thanks for any additional comment
Cor

 

[BBShark]

VetteV8 However there is no reason, I feel, why it should be not strong enough: if you are a strong man, all the power in a manual gear set-up, is indeed only going through the original pitman arm, so the load is the same, as there is no external power-assist.

An integral servo gear will transmit more torque into the pitman regardless of how strong you are.

If I were you, instead of buying a dividing head and machining the shaft, I would buy a pitman arm. This is some info I just found out.

For all looking for a correct pitman arm that will work with this conversion, I have contacted Speedway motors and verified that their pitman arm PN 91032555 is correct for this conversion. The picture below is a 74 Chevelle arn with the correct center to center, drop, spline and tapered stud hole. The Speedway arm is described as:

•5.5" center of eye to center of eye
•Splines are 1.190" outside diameter
•Bottom of tapered hole is 0.675"
•Top of tapered hole is .580"
•1.063" drop

The 1.063" drop spec is what concerned me but I sent these pictures to one of the techs at Speedway and got the following response:

Larry
It looks like the amount of drop is actually going to be .693" which look sto be very close to what you are showing in your picture from the surface it is sitting on the the bottom side of the arm where the tierod bolts on.


Craig Hardman | Street Rod Tech

 

[VetteV8]

That 's very helpful Larry!
And of course, a pitman arm of just $40 is much less than a dividing-head too.

I had already been on the SpeedwayMotors site and had noticed that there are 2 different responses to the question about the offset of this partnumber.
Their tech. Jason wrote 2 month ago:
"It is measured from center of big end to center of small end parallel"

Another response from 'unknown' is:
"This is measured from outside of big end to center of small end"
Your picture illustrates, that the second response appears to be correct, but the measured from bottom to bottom shows to be about 0.6" which is what you were looking for?

Anyhow, this must be the way I am going now. Just need to work out how I get to know their lowest shipping cost, to TX, haven't found that on their site.
Thanks again.
Cor.

BTW, other than Ebay, would there be reliable sources to obtain a Grand Cherokee gear in the US?

 

[BBShark]

That 's very helpful Larry!
And of course, a pitman arm of just $40 is much less than a dividing-head too.

I had already been on the SpeedwayMotors site and had noticed that there are 2 different responses to the question about the offset of this partnumber.
Their tech. Jason wrote 2 month ago:
"It is measured from center of big end to center of small end parallel"

Another response from 'unknown' is:
"This is measured from outside of big end to center of small end"
Your picture illustrates, that the second response appears to be correct, but the measured from bottom to bottom shows to be about 0.6" which is what you were looking for?

Anyhow, this must be the way I am going now. Just need to work out how I get to know their lowest shipping cost, to TX, haven't found that on their site.
Thanks again.
Cor.

BTW, other than Ebay, would there be reliable sources to obtain a Grand Cherokee gear in the US?

Mine actually measures .640 but I had a hard time proping it up with a screw! Also that is a cast surface to a cast surface so there is going to be some differences.

The Jeep gearbox is available rebuilt from Rock Auto. I think they are pretty reasonable and they offer a discount to VetteMod.