RebekahsZ Posted August 5, 2013 Share Posted August 5, 2013 Went to strip this past Friday night and got 10-12 passes. Last week I replaced driveshaft yoke with a cheap one from speedway, just to get some racing in while awaiting the custom driveshaft. I ran 7.11 best for the night launching off 2-step at 3,000 rpm. I marked the yoke with straight longitudinal lines with a sharpie marker before installation. Well, the yoke is already twisting again. The lines are starting to look like the lines on a peppermint stick and the metal is getting that hammered look that tells me it is failing. Next item is the chassis sheeetal. The welds and seam sealer are broken along the rear-most lap seam of the transmission tunnel. Canceling autocross plans for the weekend; car is at sheet metal/chassis fab shop to get several large scab patches welded over that joint. I guess the trans tunnel acts as a torque arm on the car. If scab patch doesn't hold I may be looking for a new chassis. I'm not ready to give up yet! Quote Link to comment Share on other sites More sharing options...
texis30O Posted August 6, 2013 Share Posted August 6, 2013 Wow you are scaring me....... I am now very worried about my set up...... Keep us updated on what the chasis shop says. Quote Link to comment Share on other sites More sharing options...
mattd428 Posted August 6, 2013 Share Posted August 6, 2013 No need for a new chassis sounds like tube chassis time. Quote Link to comment Share on other sites More sharing options...
Naptown Dave Posted August 6, 2013 Share Posted August 6, 2013 RZ do you have a cage in your car? Quote Link to comment Share on other sites More sharing options...
socorob Posted August 6, 2013 Share Posted August 6, 2013 Did you install bad dog frame rails and stitch weld the car before you put the V8 in? Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted August 6, 2013 Author Share Posted August 6, 2013 No cage (has been on the list and first priority for winter work). No bad dog rails, no stitching. But I'm rethinking. The force that I think has caused it is from the diff in the center of the car causing a flexion force thru the RT mount up (and down) at the termination of the rear half of the floorpan and forward portion of the rear floorpan forming a hinge. That hinge has flexed, fatigued and failed. It looks like an inherent weak point. The stock setup has the front of the diff supported by a crossmember that stretches across and transfers the force into the rockers. The RT mount transfers that into the tunnel alone. I wonder if I can couple the merits of the RT mount and the stock crossmember. I see the bad dog rails as being stronger in tension, not flexion. When I have the cage built, I'm curious to know of a couple of diagonals from the corner of the main hoop and seat tube to the tunnel area will help transfer some force into the cage. Input/thoughts? Quote Link to comment Share on other sites More sharing options...
mattd428 Posted August 6, 2013 Share Posted August 6, 2013 I still say tube chassis. Quote Link to comment Share on other sites More sharing options...
Domzs Posted August 6, 2013 Share Posted August 6, 2013 What he said ^^^ . It seems to me , all the standard trans LS Zs are breaking parts left and right . Thinking about switching to auto in my 83 . So far , my 78 hasn't broken anything , yet . Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted August 6, 2013 Author Share Posted August 6, 2013 You first! I just wanna drive this thing! Likely gonna miss another autocross this Saturday. Rush ordering another driveshaft yoke tonight and planning an all-nighter Friday night. Staying optimistic. Any repair done on the floors this week will be a bandaide at best. Quote Link to comment Share on other sites More sharing options...
Naptown Dave Posted August 6, 2013 Share Posted August 6, 2013 It sounds like its time to buy a welder and take some classes! Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted August 6, 2013 Author Share Posted August 6, 2013 Aw, it isn't that bad - you guys keep me both grounded and inspired-that's why I love this site. I've got my chin back off the ground and ready to get it back together. Anybody want to volunteer their car for me to learn how to weld on (?)-probably not. Honestly, I think if you do the standard JCI swap and drive it around town, the T56 option is great. But, I'm putting all of the torque down thru slicks on VHT and dropping the clutch in the torque band on an almost weekly basis-I think any car is gonna have trouble with that. Most of my friend's drag cars are POS(s) that are pretty hammered. Plus, autocrossing on slicks monthly and a couple track days a year. If you race it, it's gonna break. I brought this up to demonstrate that we not only have to think about the strength of our components, but also what we bold them to. I built this car 20 years ago and I wish I had done better foundational work, but I just can't bring myself to burn all the paint off it-that paint job almost cost me my marriage! Its a good "20-footer" even with 20 years of cone-rash, scratches, dings and a little pesky rust. I hope the new 8.8 IRS crowd have better luck, but they are dealing with 40 year-old sheetmetal too. If I ever give up on the R200, it will be for a straight axle8.8/9-inch, 4-link and a Power Glide. Meanwhile I'm thinking of a way to modify my clutch to create more consistent clutch-dumps. Quote Link to comment Share on other sites More sharing options...
duragg Posted August 6, 2013 Share Posted August 6, 2013 There is a LOT of welding on my S30 now since it is a dedicated track car. You get good at welding blow-out holes and putting out small fires pretty fast. Race-cars are race-cars for a reason. They are hammered regularly. Just keep beefing up the week spots. I think that Drag-drops have to be some of the worst abuse. Jumping burms and going Airborn at 100mph isn't great. But can't be anywhere near the force of hooking through a V8 drop from a stand still. I'd break too... Tj Quote Link to comment Share on other sites More sharing options...
Naptown Dave Posted August 6, 2013 Share Posted August 6, 2013 Between the 40 year old seam sealer, paint, rust and tin can like metal thickness learning to weld on a car is probably not the best place to start . I imagine the engineers that designed these chassis would probably faint if they saw what some of you guys are putting their babies through! I used 1.5x2.5x11ga tube to replace the 'frame rails' from the t/c buckets to the rear sub and clad the rockers with 16ga and I was worried about excessive flex and I only plan on putting around town, probably with a test and tune night at IRP here or there. Its comforting to hear that you have put your car through a fair amount abuse and are just starting to have problems. I'm surprised Matt hasen't suggested going turbo so you could launch easier and catch 'em on the big end! Quote Link to comment Share on other sites More sharing options...
mattd428 Posted August 6, 2013 Share Posted August 6, 2013 I cant suggest turbo until mine is fully operational. I have a long way to go several weekends at work to get her back to solid again. Quote Link to comment Share on other sites More sharing options...
johnc Posted August 6, 2013 Share Posted August 6, 2013 You don't need a tube frame at your power lelvels. A welded in roll bar with a vertical brace down from the diagonal/harness bar to the trans tunnel helps a bunch - especially if you add a layer of sheet metal around the tunnel to rear bulkhead connection. Also add full length subframe connectors. Quote Link to comment Share on other sites More sharing options...
texis30O Posted August 6, 2013 Share Posted August 6, 2013 (edited) @JohnC I am assuming that you make such things at your shop for one to purchase for their S30......lol???? Edited August 6, 2013 by texis30O Quote Link to comment Share on other sites More sharing options...
Zfan1 Posted August 6, 2013 Share Posted August 6, 2013 Welded in cage, done right will do wonders. I do run an auto and that is much easier on the car than a six speed. Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted August 7, 2013 Author Share Posted August 7, 2013 (edited) Dug up some options for incorporating some diff support into a rollbar per johnc's advice. In some of the pics you can see the seam that runs transversely across the floor pan from rocker to rocker up and over the hump-that is where my spine is broken. Yes, I know I should have stitch welded it, but I first built this car pre-hybridz (shoulda-woulda-coulda)! I like the crossmember at this point on the floor of the white car-thinking that might be a good idea to basically box this section of the car. John, you think Big Dog rails represent the best option for subframe connectors? Or is there something else I should consider? Edited August 7, 2013 by RebekahsZ Quote Link to comment Share on other sites More sharing options...
socorob Posted August 7, 2013 Share Posted August 7, 2013 For the 240 bad dog makes extension pieces to carry the rails back to the boxed in part near the strut towers. If you have a 280 you can go to a rear sway bar mount and make your own extension pieces. Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted August 11, 2013 Author Share Posted August 11, 2013 (edited) Finally got photos to upload. Some photos show trans tunnel damage, tearing of metal, broken spot welds, and movement along the seam. Other photos show repairs/scab patches. Then a photo shows twisting of my second cast driveshaft slip yoke. No more cheap slip yokes: have a forged one to replace this one, and the one on my custom driveshaft is nitrited billet chrome moly. Edited August 11, 2013 by RebekahsZ Quote Link to comment Share on other sites More sharing options...
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