trwebb26 Posted October 26, 2008 Share Posted October 26, 2008 I'm on my second "real" day of replacing the frame rails in my 280z. The car has full powertrain in it. I jacked it up and set it on 5 jackstands: - One on each front frame rail - a littlle behind where the front struts are. - One on each front side rear A-Arm mount - One on the transmission x-member I measured over and over to ensure that the car was level and sitting evenly on each of the jackstands. So I get done today cutting out the passenger side rail - and cleaning up the T/C bucket interface (wow was that a lot of work).... Feeling happy with my progress for the day i start sweeping up. I stick the floor broom under the car and the right rear jackstand gets caught and it comes out from under the car! The car is now just resting on 4 jackstands - and for the 5th one - the car is probably 3/8" high. I went around and checked all of the jackstands... left to right - they are set the same height - so the car definately has tweaked. The door gaps look fine, but I'm pretty concerned. Here are what I think my options are: 1) Fill the right rear of the car full of weight so it sits on the jackstand when i weld up the frame rail. 2) Cut out the left side frame rail and hope everything evens up. 3) Try lowering the transmission x-member jackstand - to see if that will put everything level again. It is possible that there was more pressure on that jackstand than the rear ones when i started this... It was impossible to tell for sure when i was setting them up. I'm pretty freaked - an help you can give me would be greatly appreciated. Quote Link to comment Share on other sites More sharing options...
palosfv3 Posted October 27, 2008 Share Posted October 27, 2008 Pics ???????. Your making things more difficult for yourself with the drivetrain in place. Your going to need complete access to all rail areas for proper cleaning and welding. The additional stresses of the engine & trans weight can shift or twist the unistructure when apart. I believe there are unibody dimensions posted somewhere on this site. Get a copy .Then you can make up a set of centerline guages and check the datum plane measurements for twist and sag as you go. There is much to be aware of when doing this type of repair. Quote Link to comment Share on other sites More sharing options...
johnc Posted October 27, 2008 Share Posted October 27, 2008 Don't freak, the car is fine. You want the car square and level and not resting on the parts you're trying to replace. Carefully jack the car up and place the jackstands under the rocker panels (assuming theya re in good condition) in front and back and then lever the car again, measuring at the rocker panels. Place you're 5th jackstand under the front crossmember with just a light load on it. Quote Link to comment Share on other sites More sharing options...
trwebb26 Posted October 27, 2008 Author Share Posted October 27, 2008 John, Thanks for the reply! I like the idea of putting jackstands under the rockers because all of the jackstands would be the same height. A support on the rear subframe isn't needed? I remember when i had the engine/trans out one time - and the car was REALLY rear end heavy (I could easily pick up the front of the car). Quote Link to comment Share on other sites More sharing options...
trwebb26 Posted October 31, 2008 Author Share Posted October 31, 2008 An update on my problem... I took John's advice and set the jackstands under the 4-corners of the rockers. With just these four jackstands - the door gaps were aweful. If you jack up the front of the car (like John suggests) until the front frame rails are level then the door gaps will be perfect and everything will be right. Things to take away when doing this: - Buy a bunch of sheet steel and wood of varying thickness. Floors in general are not level due to settling, wear, cracks, manufacturing tolerance, and drainage... I used a bunch of sheets of 18ga steel and 1x10 wood under each of the jackstands to get everything perfect. - Be patient... it is amazing how changing the height of one jackstand by 1mm will tweak the car - and it doesn't take a lot to make a noticable difference. - Measure several places! Highs and lows are everywhere and where you measure as level on one place of the rocker may show it off on another. - Get the four rocker jackstands perfect before screwing around with the front of the car. - I had to put the jackstands under the radiator x-member in order to get the front frame rails level. Jacking up on the front x-member just picked the car up off of the front side rocker jackstands. My front side jackstand is sitting on the radiator x-member. - I tried to put a jackstand under the diff - but (like John has suggested) it had a very slight (if any) affect. I left it there with some slight pressure as a safety measure to keep the car up in the air in case the front end gets light for some reason. -Tim Quote Link to comment Share on other sites More sharing options...
johnc Posted October 31, 2008 Share Posted October 31, 2008 Two things to learn from this: 1. Its orders of magnitude better to remove the complete driveline before attempting frame work. 2. It takes buttloads of time setting up/preparing for just about any frame work. Quote Link to comment Share on other sites More sharing options...
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