Guest cap110680 Posted March 10, 2005 Share Posted March 10, 2005 hey guys, when i installed my my 350/700r4 in my 74 260z i didnt measure to see if the drivetrain was parellel. i didnt even think about the motor mounts being sloted so i just dropped it in. i measured from the center of the harmonic balancer to the frame rail and from the center of the trans bolt to the frame rail and they are about 3/4 of an inch off. so my question is what will happen if i run it like that? wont the drive shaft make up for the difference? i am asking because i know on 4wd the driveshaft is not always perfectly inline with the diff. anyway i feel really dumb for not measureing it and i already have my exhaust, linkages,line etc done. please help me.. thanx chris Quote Link to comment Share on other sites More sharing options...
2126 Posted March 10, 2005 Share Posted March 10, 2005 It will work for sure, but with a less than aligned situation you will shorten the life of your driveshaft U-joints and if you tend to do dragstrip type launches, you may wind up with a broken driveshaft. My recommendation is to spend the time and readjust it as best you can. Quote Link to comment Share on other sites More sharing options...
Guest Aaron Posted March 10, 2005 Share Posted March 10, 2005 Also, if the two ujoints angles are not the same you could have major vibration issues. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted March 10, 2005 Share Posted March 10, 2005 If you draw an imaginary line straight out of the back of the transmission yoke and a second line straight out of the diff yoke, they should be parrallel. So if the engine and trans are angled slightly right to left, then that is OK as long as the diff is angled in the same direction. Same for the up-down angles. If the two lines are not parrallel, you will get driveline vibrations like said above. The drive shafts on a Z are relatively short and, because of the generally low (high numerical) rear gear ratios they spin at higher RPM's than a car with say a 3.08 rear diff. All of this makes the alignment more critical. You aren't screwed yet. If you did the JTR style trans mount, then you can easily slot the trans bolt hole in the crossmember to align the engine right to left if needed. Some washers in the trans or diff mount can adjust the up down angles. Get the car finished and see if you have any vibrations when accelerating at speed. Quote Link to comment Share on other sites More sharing options...
Guest cap110680 Posted March 10, 2005 Share Posted March 10, 2005 so are you saying i should leave as is and test drive it first? then change it if it vibrates, or should i change it now. also are the frame rails a accurate way of telling if the front of the engine and the back of the trans are parellel? or is it better to just deal with the trans and the diff? thanx chris Quote Link to comment Share on other sites More sharing options...
SpeedRacer Posted March 10, 2005 Share Posted March 10, 2005 If you used the JTR method it shifts the engine over to the right just about ¾â€. This is to provide clearance on the driver’s side so the headers don't hit the steering column. I’d just slot the trans mount so it is centered and not worry about the engine. BTW, lots of production cars shift the engine over to the right (passenger side) for the very same reason. Quote Link to comment Share on other sites More sharing options...
Guest tony78_280z Posted March 10, 2005 Share Posted March 10, 2005 You could baby it for a short time and not drive it like you want to, but you need to get it fixed asap. A broken drive shaft is no fun. Quote Link to comment Share on other sites More sharing options...
Guest cap110680 Posted March 10, 2005 Share Posted March 10, 2005 what is the best method to slot that trans mount? it is so thick Quote Link to comment Share on other sites More sharing options...
mark Posted March 10, 2005 Share Posted March 10, 2005 The frame rails are hardly ever true on a 30 + year old car. I would bet that part of the difference you are seeing is in the technique you are using to measure. Try again and see if the results are the same. Also try a string from the front of the crank under the car to the output shaft on the trany and see how that lines up with the diff. Speed Racer has the best idea, put it together and drive it. If no vibration, your good. Mark Quote Link to comment Share on other sites More sharing options...
SpeedRacer Posted March 10, 2005 Share Posted March 10, 2005 At 3/4 of an inch you could probably just drill a new hole in the right place. Quote Link to comment Share on other sites More sharing options...
Guest cap110680 Posted March 10, 2005 Share Posted March 10, 2005 i guess i will have to get it running and drive it then. i wont step on it till i am sure it is ok. here are some old pics of my z, i have to update them: http://groups.msn.com/vintagechevyvanclub2/chris69a108.msnw?Page=3 thanx for all the comments and help, i will post when i get the damn thing running. chris Quote Link to comment Share on other sites More sharing options...
2126 Posted March 10, 2005 Share Posted March 10, 2005 Also, if the two ujoints angles are not the same you could have major vibration issues. Chris, Aaron is correct about the vibration. You may not notice it too much at lower speeds and under small loads, but you are more likely to hear and feel a vibration under heavier loading (putting your foot in it!) and at some higher speed. Usually, there will be a frequency (a particular speed the driveshaft is rotating) that the U-joints will resonate (at the resonate frequency the vibration will increase significantly) and will become obvious to you. For testing purposes only, it should be OK to put it under load to see if you have a vibration...I don't recommend leaving it that why for very long if you do in fact discover a vibration in the driveshaft. If we meet this weekend, we can discuss it further. Tom Quote Link to comment Share on other sites More sharing options...
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