Home » Public Forums » GMCnet » Re: [GMCnet] Variable Ratio Steering Box
| Re: [GMCnet] Variable Ratio Steering Box [message #304425] |
Thu, 28 July 2016 11:10  |
Tom Whitton
Messages: 235
Registered: February 2004
Location: Paducah, KY
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I need a new steering box and looked up variable ratio steering. Here's the definition from Wikipedia:
"At the center of the rack, the space between the teeth are smaller and the space becomes larger as the pinion moves down the rack. In the middle of the rack there is a higher ratio and the ratio becomes lower as the steering wheel is turned towards lock. This makes the steering less sensitive when the steering wheel is close to its center position and makes it harder for the driver to oversteer at high speeds."
I'm not sure this is exactly what is available for our coaches. We don't have rack and pinion steering. Regardless, if the available variable ratio boxes do the same thing ((reduce oversteer), it sounds like a good thing to have. Apparently variable ratio wasn't available when these coaches were new. Has anyone had problems with a variable ratio steering box? Do you like it? Where did you get it?
Look forward to hearing,,
Tom Whitton
26 foot updated GMC
Paducah, KY
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| Re: [GMCnet] Variable Ratio Steering Box [message #304426 is a reply to message #304425] |
Thu, 28 July 2016 11:28  |
powerjon
Messages: 2446
Registered: January 2004
Karma: 5
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Tom,
As with most parts for your coach, Jim K carries both the Fixed Ratio and a Variable ratio box.
http://www.appliedgmc.com/prod.itml/icOid/638
http://www.appliedgmc.com/prod.itml/icOid/639
You can buy them else where and I do have a lead on a rebuilt FIXED ration if you are interested which is not that far from you. Contact me PM if your interested.
JR Wright
78 Buskirk Stretch
75 Avion
Michigan
> On Jul 28, 2016, at 12:10 PM, Tom Whitton wrote:
>
> I need a new steering box and looked up variable ratio steering. Here's the definition from Wikipedia:
>
> "At the center of the rack, the space between the teeth are smaller and the space becomes larger as the pinion moves down the rack. In the middle of the rack there is a higher ratio and the ratio becomes lower as the steering wheel is turned towards lock. This makes the steering less sensitive when the steering wheel is close to its center position and makes it harder for the driver to oversteer at high speeds."
>
> I'm not sure this is exactly what is available for our coaches. We don't have rack and pinion steering. Regardless, if the available variable ratio boxes do the same thing ((reduce oversteer), it sounds like a good thing to have. Apparently variable ratio wasn't available when these coaches were new. Has anyone had problems with a variable ratio steering box? Do you like it? Where did you get it?
>
> Look forward to hearing,,
>
> Tom Whitton
> 26 foot updated GMC
> Paducah, KY
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GMC GreatLaker
GMC Eastern States
GMCMI
78 30' Buskirk Stretch
75 Avion Under Reconstruction
Michigan
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| Re: [GMCnet] Variable Ratio Steering Box [message #304428 is a reply to message #304425] |
Thu, 28 July 2016 11:32 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Tom,
I have no experience with the variable ratio boxes for the GMC. But, let
me assure you that we DO have Rack and Pinion steering: Inside that
innocuous looking box is a short Rack which also serves as a hydraulic
piston, with sophisticated valving inside. The steering column input is a
screw which moves the piston -- with assist from the valve-regulated
hydraulic pressure from the PS pump. As the piston/Rack moves it rotates
the Pinion on the end of the Pitman Arm shaft. So, all the elements of a
Rack and Pinion system are there and can be manipulated as described in
your quotation.
I must say, however, it really might be more appropriately called a Pinon
and Rack since it's sort of upside down compared to a Rack and Pinion as we
usually think of it.
Ken H.
On Thu, Jul 28, 2016 at 12:10 PM, Tom Whitton
wrote:
> I need a new steering box and looked up variable ratio steering. Here's
> the definition from Wikipedia:
>
> "At the center of the rack, the space between the teeth are smaller and
> the space becomes larger as the pinion moves down the rack. In the middle
> of the rack there is a higher ratio and the ratio becomes lower as the
> steering wheel is turned towards lock. This makes the steering less
> sensitive when the steering wheel is close to its center position and makes
> it harder for the driver to oversteer at high speeds."
>
> I'm not sure this is exactly what is available for our coaches. We don't
> have rack and pinion steering. Regardless, if the available variable ratio
> boxes do the same thing ((reduce oversteer), it sounds like a good thing to
> have. Apparently variable ratio wasn't available when these coaches were
> new. Has anyone had problems with a variable ratio steering box? Do you
> like it? Where did you get it?
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] Variable Ratio Steering Box [message #304437 is a reply to message #304425] |
Thu, 28 July 2016 12:35 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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You have lots of experience with VR steering. All modern cars have them. GM went to them in early 70s but not in trucks/ heavy vehicles. I went to a JimK VR box a few years ago and it really updates the feel. At about 1/4 turn either side of centre you notice the incresed response. They shyed away from VR in higher weight and higher CG Vehicles to prevent or discourage excessive driver input upsetting the handling and causing loss of control or rollover. The converse is that better response may help you avoid an accident, if you know how to drive. I have a 91 S15 SLT and that has fixed ratio PS even though it is a 90s truck with factory Bilsteins but as 4x4 may have higher CG. I plan to update it. You really better be sure your box is in high point if you go VR or you will really have odd handling.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Variable Ratio Steering Box [message #304438 is a reply to message #304428] |
Thu, 28 July 2016 12:37 |
Keith V
Messages: 2337
Registered: March 2008
Location: Mounds View,MN
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I think it's actually called recirculating ball on a relay arm isn't it?
The major difference between our steering and a R&P is the relay arms that connect everything together with their plethora of joints and subsequent flexibility.
A Rack and Pinion has the rack connected directly to the wheels using only 2 joints per side and those joints are normal to the applied force rather than being twisted and rotated all over the place.
Too many degrees of freedom makes steering a sloppy boy
>
> Tom,
>
> I have no experience with the variable ratio boxes for the GMC. But, let
> me assure you that we DO have Rack and Pinion steering: Inside that
> innocuous looking box is a short Rack which also serves as a hydraulic
> piston, with sophisticated valving inside. The steering column input is a
> screw which moves the piston -- with assist from the valve-regulated
> hydraulic pressure from the PS pump. As the piston/Rack moves it rotates
> the Pinion on the end of the Pitman Arm shaft. So, all the elements of a
> Rack and Pinion system are there and can be manipulated as described in
> your quotation.
>
> I must say, however, it really might be more appropriately called a Pinon
> and Rack since it's sort of upside down compared to a Rack and Pinion as we
> usually think of it.
>
> Ken H.
>
>
> On Thu, Jul 28, 2016 at 12:10 PM, Tom Whitton
> wrote:
>
>> I need a new steering box and looked up variable ratio steering. Here's
>> the definition from Wikipedia:
>>
>> "At the center of the rack, the space between the teeth are smaller and
>> the space becomes larger as the pinion moves down the rack. In the middle
>> of the rack there is a higher ratio and the ratio becomes lower as the
>> steering wheel is turned towards lock. This makes the steering less
>> sensitive when the steering wheel is close to its center position and makes
>> it harder for the driver to oversteer at high speeds."
>>
>> I'm not sure this is exactly what is available for our coaches. We don't
>> have rack and pinion steering. Regardless, if the available variable ratio
>> boxes do the same thing ((reduce oversteer), it sounds like a good thing to
>> have. Apparently variable ratio wasn't available when these coaches were
>> new. Has anyone had problems with a variable ratio steering box? Do you
>> like it? Where did you get it?
>>
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Keith Vasilakes
Mounds View. MN
75 ex Royale GMC
ask me about MicroLevel
Cell, 763-732-3419
My427v8@hotmail.com
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| Re: [GMCnet] Variable Ratio Steering Box [message #304447 is a reply to message #304425] |
Thu, 28 July 2016 15:01 |
Tom Whitton
Messages: 235
Registered: February 2004
Location: Paducah, KY
Karma: 0
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Ken,
You're right, we do have sort of rack and pinion steering but, as you said, it is better described as "pinion and rack" since the rack drives the pinion. I wish it was more like modern rack and steering but that's a wish that isn't going to come true.
I'm leaning toward a variable ratio box but would like to know if there's a downside. If not, I'm going for it.
Does anyone know of a downside for a variable ratio steering box?
On a completely different subject, yesterday I topped off my gas tanks at Sam's because gas prices started to inch up a little. It took less than 10-gallons to fill up but I was there for about 45-minutes talking to the people who got out of their cars to come over and ask about the coach. (With all the work we put into these machines, it feels good to get compliments.) One sixty-something couple, driving a late model Caddy SUV, looked the coach over for several minutes. Another man and wife asked all kinds of questions. They were from here and I took them for an inside tour. Two other men walked around and stopped to ask what year it was. All I can say is it's obvious that there is a lot of interest in these coaches. It's probably a good idea to carry a few of the GMC Motorhome brochures along, which I haven't done but we all should.
Thanks,
Tom Whitton
26 foot updated GMC
Paducah, KY
Message: 7
Date: Thu, 28 Jul 2016 12:32:10 -0400
From: Ken Henderson
To: gmclist@list.gmcnet.org
Subject: Re: [GMCnet] Variable Ratio Steering Box
Message-ID:
Content-Type: text/plain; charset=UTF-8
Tom,
I have no experience with the variable ratio boxes for the GMC. But, let
me assure you that we DO have Rack and Pinion steering: Inside that
innocuous looking box is a short Rack which also serves as a hydraulic
piston, with sophisticated valving inside. The steering column input is a
screw which moves the piston -- with assist from the valve-regulated
hydraulic pressure from the PS pump. As the piston/Rack moves it rotates
the Pinion on the end of the Pitman Arm shaft. So, all the elements of a
Rack and Pinion system are there and can be manipulated as described in
your quotation.
I must say, however, it really might be more appropriately called a Pinon
and Rack since it's sort of upside down compared to a Rack and Pinion as we
usually think of it.
Ken H.
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| Re: [GMCnet] Variable Ratio Steering Box [message #304448 is a reply to message #304438] |
Thu, 28 July 2016 14:59 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Our steering, in addition to being a variation on rack and pinion is,
indeed, of the recirculating ball type. That's merely a way of reducing
the friction on the worm gear driving the piston/rack. Recirculating balls
were used long before power steering became common, and can be applied to
many of the steering gear variants, even some of these, which are
essentially obsolete:
Cam and Lever
Cam and Roller
Worm and Ball
Cam and Peg
Worm and Roller
Screw and Nut
Worm and Sector
The more conventional "rack and pinion", employing a long lateral rack with
a pinion directly attached to the steering column certainly does lend
itself to much less complicated and "slop prone" linkage.
Ken H.
On Thu, Jul 28, 2016 at 1:37 PM, Keith V wrote:
> I think it's actually called recirculating ball on a relay arm isn't it?
>
> The major difference between our steering and a R&P is the relay arms that
> connect everything together with their plethora of joints and subsequent
> flexibility.
> A Rack and Pinion has the rack connected directly to the wheels using only
> 2 joints per side and those joints are normal to the applied force rather
> than being twisted and rotated all over the place.
>
> Too many degrees of freedom makes steering a sloppy boy
>
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] Variable Ratio Steering Box [message #304471 is a reply to message #304461] |
Thu, 28 July 2016 20:04 |
xplorid
Messages: 213
Registered: February 2012
Location: Boise
Karma: 0
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Hi Karen - mostly highway speeds are now comfortable driving, less twitchy, just don't think about the steering anymore. Drives like my Chrysler minivan now, a modern feel. The box I replaced was not broken, so the difference is attributable to the variable ratio. OBTW I am in San Jose at the moment if you are around.
1974/94 GMCII by Explorer
Manny 6.5 TD Al radiator
1 ton front 4 bags back
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| Re: [GMCnet] Variable Ratio Steering Box [message #304485 is a reply to message #304471] |
Thu, 28 July 2016 23:50 |
TR 1
Messages: 348
Registered: August 2015
Location: DFW
Karma: -7
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xplorid wrote on Thu, 28 July 2016 20:04Hi Karen - mostly highway speeds are now comfortable driving, less twitchy, just don't think about the steering anymore. Drives like my Chrysler minivan now, a modern feel. The box I replaced was not broken, so the difference is attributable to the variable ratio. OBTW I am in San Jose at the moment if you are around.
You had said "despite the price"... Mind my asking what the Manny steering box goes for?
Mark S. '73 Painted Desert,
Manny 1 Ton Front End,
Howell Injection,
Leigh Harrison 4bag and Rear Brakes,
Fort Worth, TX
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| Re: [GMCnet] Variable Ratio Steering Box [message #304541 is a reply to message #304536] |
Fri, 29 July 2016 14:47 |
Keith V
Messages: 2337
Registered: March 2008
Location: Mounds View,MN
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Maybe it's time we do a true Rack and pinion conversion.
I did one on my Vette, so much better.
Biggest question is where to source a heavy duty rack
>
> G'day,
>
> I just got off the phone with Manny and he advised;
>
> 1) He placed an order with Saginaw for 40 GMC steering boxes in 2008.
> 2) He has 1 or 2 left and since it took him seven years to sell them he probably will not be placing another order.
> 3) They are variable ratio
> 4) They are $693.00 each
>
> Regards,
> Rob M.
> USAussie - Downunder
> AUS '75 Avion - The Blue Streak TZE365V100428
> USA '75 Avion - Double Trouble TZE365V100426
>
>
>
>
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Keith Vasilakes
Mounds View. MN
75 ex Royale GMC
ask me about MicroLevel
Cell, 763-732-3419
My427v8@hotmail.com
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| Re: [GMCnet] Variable Ratio Steering Box [message #304543 is a reply to message #304536] |
Fri, 29 July 2016 14:55 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Too bad Manny never advertises his product; he'd probably have sold a lot
more of those boxes -- and all his other neat stuff. :-)
If you read Don Wirth's steering box paper, you'll see that it is
relatively easy to change the ratio of the OEM box. He doesn't mention it,
but I suspect one could also change to variable ratio. Because the rack's
tooth spacing varies as the ratio changes, it would be necessary to change
the piston/rack as well as the lead screw. But, since the innards of all
the boxes seem to be interchangeable (aside from stops), I'd expect that to
be no problem. Just a WAG tho'.
http://www.gmceast.com/technical/Wirth_GMCMH_Steering_Box.pdf
Ken H.
On Fri, Jul 29, 2016 at 11:09 PM, Rob Mueller
wrote:
> G'day,
>
> I just got off the phone with Manny and he advised;
>
> 1) He placed an order with Saginaw for 40 GMC steering boxes in 2008.
> 2) He has 1 or 2 left and since it took him seven years to sell them he
> probably will not be placing another order.
> 3) They are variable ratio
> 4) They are $693.00 each
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] Variable Ratio Steering Box [message #304563 is a reply to message #304425] |
Fri, 29 July 2016 21:09 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Be thankful you DON'T have true rack and pinion steering. They fail way more often than our Saginaw boxes. Dirt erodes seals and constant leaks. Better suited for transverse engine FWD where they try to eliminate as many parts as possible. I think our setups are better for isolating road shock and torque steer from the driver. I see no reason not to upgrade to VR unless you are a bad driver who overcorrects in a panic situation. The slower ratio factory setup helps insulate you from doing that.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Variable Ratio Steering Box [message #304585 is a reply to message #304557] |
Sat, 30 July 2016 12:32 |
KB
Messages: 1262
Registered: September 2009
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KB wrote on Fri, 29 July 2016 17:41xplorid wrote on Fri, 29 July 2016 10:04Manny's is about $700, might be limited quantity left
Looks like Applied has rebuilt variable ratio ones for about $400:
http://appliedgmc.com/prod.itml/icOid/639
Don't know if they have new ones too; they're mentioned, but there's no price listed.
Karen
1975 26'
just for the record, Applied has rebuilt variable ratio ones with a $250 core charge,
but no new ones. Jim said he got them from Manny, and Manny doesn't have anymore.
It sounds like the only really unique part of the MH box is the exterior shell,
and the guts are all the same. I think that means if you could find the correct variable
ratio steering gear, you could swap it into the MH shell yourself. The question though,
is which vehicles had the correct variable ratio innards?
thanks,
Karen
1975 26'
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