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Discussion in 'Classic Mustang Specific Tech' started by 71vert-pga, Jul 4, 2004.
Will do! Thanks.
Looks like the crossmember has to go.
Then I would just switch out your original box for a quicker steering saginaw box from a different vehicle or just have the stock one freshened up and be happy with it. I would not cut the crossmember out of a 71 convertible for minimal gains.
Is the 71-73 crossmember similar to this? This is a 1967 Fairlane in which a TCP rack was installed. The crossmember was not completely removed but the back portion was cut away to make room for the rack and expose the lower control arm mounts for the rack brackets.
We will be accepting delivery of a 71-73 shell at work within the next month for product development. I don't have a solid timeframe for completion but things are moving very quickly after all the recent changes.
Edited to get rid of some extra words.
Looks pretty close. It's a welded unit. Brion Gluck at Dark Horse Racing completely removed his crossmember for the TCP rack.
I may not need to do this with the j-car rack. Brion's going to send me some more details on his installation. I'll take some more measurements after I hear from him next. I had been thinking about removing only part such as you did.
BTW, how much did you trim off and do you have any more photos?
this thread is cool!
yes, i used the stock exhaust manifolds in chepie to clear the steering shafts. My only other advice is to watch the inner tie rod end location, so as not to create bump steer.
My goal is (if at all possible) to mount the rack so that my new fabricated centerlink is in the same location as the original. That way the original geometry will be the same and there shouldn't be any more bumpsteer than the car had to begin with.
And I can certainly live with that!
Stock Saginaw box upgrade
For those who might be interested, here is a tech note from Dark Horse Racing.
- 1971-1973 manual boxes used a differently shaped external casting with a 1 1/8" sector and 24:1 ratio. There also used a slightly different frame mounting bolt pattern they won't interchange with 67-70 models.
- The 71-73 worm and rack assembly is identical to the 70-82 Corvette piece. The Corvette sector (GM P/N 7812838) and worm (GM P/N 7812942) will fit in 71-73 1 1/8" boxes if a new groove is scribed into the Ford pitman arm that corresponds with the index on the GM sector and if a Corvette coupler (GM P/N 7806391) is substituted for the Ford rag joint. Provides 16:1 ratio rather 24:1 ratio. Also the flat Ford-style sector shaft cover can be replaced with the 'Vette cover (GM P/N 7806748) which has an integral bushing that lends additional support to the sector shaft. The outer rim of the bushing support must be turned down to fit in the Ford box.
However, I spoke with Brion last night and he feels the TCP rack conversion on his racecar is one of the biggest improvements he's done.
I really looked hard at doing a Rack install on my 73 convertible. I don't think that it would be wise to cutout the crossmember that runs under the engine on the front of our cars. They are very heavy convertibles and it would not be cool to do anything that might reduce the structural integraty of the vehicale. Okay with that said I'm afraid that I haven't made to much progress on my R&P conversion. I got side tracked, but hopefully I can start back in on it in a couple weeks.
I will admit I have some concerns about the strength of the R&P units out of the smaller cars. I was interested in using a rack from a dodge intrepid but I have not been able to find one here in Lubbock and have never gotton any specs for that rack from any of the sources I contacted about it.
I had a really long thread about my search for information on a R&P install, but I think that 71vert has covered all that information already. Like him I decided that it would be best to use a rack that I could attach a center link to. It is too bad that he doesn't live closer we could really help each other out with this.
check this out
Its not for a 71 conv. but it is still a relevant link.
As for the cross member, on any car really, why does the cross support have to be touched? If anything a stronger unit should be installed and the rack can be mounted seperately altogether. I wish my car had a brace that size, mine only has a little tube with a bolt on each end and it does not tie into the lower arm mounts like the fairlane picture does.
That is the point I was trying to make earlier, the J-rack can be mounted off center with a spacer between it and the center link, like in the trinitymustang link or the TCP setup. It really is a challenge to lay under the car, hold up the rack and decide where to start.
I think that's some of Sixto's early stuff on that link.
I would not remove the crossmember without fabricating another to go in it’s place, only slightly farther forward. Just far enough to allow space for the new assembly. I don’t want to do anything to weaken the structural integrity of the car.
The whole point of this operation is to make these cars better than the technology of the day gave us. And that means they also need to be stronger they were originally designed to be. Stronger, safer, more responsive. That's something we all want to achieve.
It can be done. And we’re jus’ the kinda guys to do it.
Ok, did some more research and talked to several people who have either done this already, are in the process of doing it, or will start soon. So far no one has any regrets at all.
Duane Simon used a stock flex-link from a Buick Centry. Don't know what year but the pictures he sent make it look like a factory install. He did some modification to the end of the Mustang shaft which would be required no matter which system we chose to use. He removed the crossmember (like everyone else) and positioned the rack forward so that the centerlink he fabricated would connect to the inner tierods in the same place as the original linkage to eliminate issues with bumpsteer.
The link is solid and shouldn't cost more that a few bucks from a local salvage yard.
Most of the rack mods I like have the steering column shortened to end at the firewall with a u-joint half shaft continuing from there down to the rack input.
Flex link? Got Pictures?
I remember a few years back, Sacramento Mustang was selling a $1000 R&P kit, one of the first commercial designs and it didn't last long. Their system had a "flex shaft" that was used to snake the steering shaft around the exhaust manifold to the rack input. Kinda like an overgrown speedo cable.
The exhaust seems to be a big obstacle in this kind of set-up. I can't see going back to stock maifolds just to have R&P steering. I currently have full length headmans and just holding the steering rack up to the drivers side header looks bad for the home team. I think as far as full length headers go, tri-Ys would be the best to work around. The next best thing (performance wise) would be shorties. Again, this is why I favor the GM rack because it can be mounted way over next to the frame rail and have the center link attached offset (centered in car). Doing it like this (hopefully) lowers the steering shaft angle of approach enough to allow using a half shaft with good quality u-joints on both ends.
Duane has full length headers on his car with with no clearance problems.
Here's another image he sent to me from the initial set-up.
o.k. looking at the picture of the steering shaft linkage see how the original steering extends out of the firewall a few inches? If that is shortened back to the firewall, it will lessen the angle that the half shaft u-joints operate in. I remember reading about the maximum angle that you don't wanna exceed on those joints, but I can't remember the specifics. I'll see if I can find a picture of a shortened steering shaft.
Like I said, this link is a stock GM part that was built to last forever.
I had plans to go to the salvage yard yesterday to find one for myself but I couldn't convince my wife that it was a great way to spend our fourth anniversary. I guess some women just lack the ability to prioritize.
I believe the "max" angle is 40 degrees but I want to stay well within 30 degrees. Duane did not shorten the column shaft at all. His setup works great and is nowhere near the point of binding. We could easily come back another inch or two on the column to make the angles even smoother if desired.
Re: the 71-73 Mustang Saginaw box. I sent a box to AGR Steering to be reworked two years ago and they were able to rebuild it with 12:1 ratio, high-effort components that matched the WS6 TransAm/Z28 internals. Cost was about $400, IIRC. Car was amazingly transformed.
Psydwaze, looks like I can easily trim just over an inch from my stock crossmember without affecting the units strength in the least bit. It could be cut back as far as you did on the image you posted but I don't feel that will be necessary.
This would provide enough space for the j-car rack to be placed about as far forward as possible. I can then attach the tierods to the rear (somewhat like randall or duane) and still have plenty of room for headers if I choose to go that route someday. My centerlink would be about an inch farther back than original but the effects of that should be relatively easy to adjust for.
BTW, I can't get my attachments to post "inside the frame" like you seasoned Pro's do. What's the trick?
A word of caution on the flex shafts. If they are run too close to extreme heat (headers) they can fail. I haven't seen one break but have heard that the laminant or coating that holds the cables together breaks down after many heat cycles. The breakage usually occurs during high stress, such as turning the wheels with the car stopped or during a three point turn.
On the rack options, due to the narrow centerlink mount of the J-rack and other center take-off OEM racks, it is necessary to extend or reposition the centerlink. This leaves the door open for deflection. You will always have off axis forces because the tie-rod is not perfectly inline with centerlink. It would be interesting to see if there is a measurable amount of deflection in the long end of the centerlink or the wrap around mounted centerlink. This flexing will have some effect on the responsiveness of the steering and may also end up with some fatigue issues after extended use. I have only seen one aftermarket design using an OEM rack that has addressed this issue by adding a support to the long end of the centerlink. Without actually seeing this unit in person I cannot fairly comment on the strength or ridgidity of the support. But at a glance it appears to the be one of the better bandaids when using an OEM rack.