Crow Posted July 11, 2009 Share Posted July 11, 2009 I'm going to swap my TH350 for the 700R4 and know I have to move the cross member and shorten the driveshaft, but thats all I know. I searched a bit but still wonder what the length should be in my '72. I also wondered if there is a driveshaft from another model GM that I could swap in without modifying? Any suggestions as to what yoke and u-joints I should replace my stock parts for? I'm 95% street and have a crate motor advertising 450ft/lb peak. Quote Link to comment Share on other sites More sharing options...
monte70car Posted July 11, 2009 Share Posted July 11, 2009 There was a post a few months back on how long the a drive shaft should be and where the cross member needs to be moved to. Quote Link to comment Share on other sites More sharing options...
CrazyDavey Posted July 11, 2009 Share Posted July 11, 2009 There was a post a few months back on how long the a drive shaft should be and where the cross member needs to be moved to. Rob, did you try a search? I typed in "driveshaft lenght" and got quite a few threads....Dave Quote Link to comment Share on other sites More sharing options...
monte70car Posted July 11, 2009 Share Posted July 11, 2009 Should see a post there I made Dave I covered the th400 th350 and the 7004r. Quote Link to comment Share on other sites More sharing options...
Crow Posted July 11, 2009 Author Share Posted July 11, 2009 Thanks, still haven't got the trans yet, was hoping to get the shaft done now, but probably right to wait and see. Anyone have a solid 700R4 for sale? Still looking for quality and price here in Canada. Quote Link to comment Share on other sites More sharing options...
CrazyDavey Posted July 11, 2009 Share Posted July 11, 2009 Should see a post there I made Dave I covered the th400 th350 and the 7004r. well there ya go.... ...sorry Rob, I missed the top of the post!!! Quote Link to comment Share on other sites More sharing options...
monte70car Posted July 11, 2009 Share Posted July 11, 2009 and here is the post I did just last year on it http://www.firstgenmc.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=148485#Post148485 Quote Link to comment Share on other sites More sharing options...
Crow Posted July 11, 2009 Author Share Posted July 11, 2009 Like all things with older cars, I would suggest you install the trans and measure. No matter how many people tell you it will be a certain size, worn bushings and mounts could affect the final measurement. As far as the cross member, you should be able to slide it back to the furthest mounting hole and make it work. Some have found that you also need to remove the rubber bushings that the crossmember goes in to allow for enough room on top that the tunnel does not need to be beat into submission. I do have a driveshaft that is cut for a 700R4 and can give you the measurements off of that but I strongly suggest that you install, measure and then have it cut. I wondered if the was any 'massaging' that needed to be done to the floor to make it fit, a buddy said he had to beat the hell out of his Chevelle floor. Quote Link to comment Share on other sites More sharing options...
Crow Posted July 11, 2009 Author Share Posted July 11, 2009 and here is the post I did just last year on it http://www.firstgenmc.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=148485#Post148485 Thanks Rob, I'm stuck on dial up, so you saved me an hour or so. Chris. Quote Link to comment Share on other sites More sharing options...
kc8oye Posted July 11, 2009 Share Posted July 11, 2009 I swapped my TH350 for a 700r4.. *NO* mods are required to the floor pan. I use an impala crossmember that bolts to the frame w/o rubber bushings, and I just slid it back to another set of holes and that was that. I re-used my TH350 driveshaft yoke as they are a little bit stronger then a700r4 unit, and are the same spline count and diameter. I had to have 6" taken out of my driveshaft.. but like allan said, you need to measure. Best thing to do is find a machine shop that will do the work, and then find out how they want you to measure. Mine told me center of the ujoint to center of the ujoint. make sure you have your driveshaft rebalanced too! Quote Link to comment Share on other sites More sharing options...
kc8oye Posted July 12, 2009 Share Posted July 12, 2009 The shop I dealt with offered to balance it and I turned it down at first due to the lack of funds... I later had it balanced due to the severe vibrations ~ Quote Link to comment Share on other sites More sharing options...
680HPStroker Posted July 21, 2009 Share Posted July 21, 2009 Go to a reputable tranny shop that has done a lot of these swaps and have them measure for you, sent your driveshaft off to be modified, and then have the same shop re-install your driveshaft for you with new Spicer 1350 series u-joints on both ends. That way if they screw it up they will have to replace your driveshaft. Quote Link to comment Share on other sites More sharing options...
Crow Posted July 22, 2009 Author Share Posted July 22, 2009 Thanks for the tips guys, decided to keep it simple for now to get the car done sooner and rebuilt the th350, kept the cost and possible headaches down to half almost, will worry about mileage later... Quote Link to comment Share on other sites More sharing options...
680HPStroker Posted July 22, 2009 Share Posted July 22, 2009 If you do all the install work you can keep a 700R4 swap to under $1K for a mild street build. Even a turn key job at around $1.5K is still not bad considering you have to deal with nothing. Either way you get to enjoy better milage and lower rpm's which means less wear and tear. I've had two 700R4 trannies in the past and NEVER regreted it. I'd still have one if I wouldn't have got scarred about my last one being able to hold up to my power level while being beat at a drag strip. I'm actually thinking about a full manual 4L80, or maybe a 6L80 if I end up keeping my car. Unless you are racing for low et who gives a rats hind end about weight. In bracket racing consistancy wins races/money. Quote Link to comment Share on other sites More sharing options...
680HPStroker Posted July 22, 2009 Share Posted July 22, 2009 If you do all the install work you can keep a 700R4 swap to under $1K for a mild street build. Even a turn key job at around $1.5K is still not bad considering you have to deal with nothing. Either way you get to enjoy better milage and lower rpm's which means less wear and tear. I've had two 700R4 trannies in the past and NEVER regreted it. I'd still have one if I wouldn't have got scarred about my last one being able to hold up to my power level while being beat at a drag strip. I'm actually thinking about a full manual 4L80, or maybe a 6L80 if I end up keeping my car. Unless you are racing for low et who gives a rats hind end about weight. In bracket racing consistancy wins races/money. Quote Link to comment Share on other sites More sharing options...
kc8oye Posted July 24, 2009 Share Posted July 24, 2009 i put the 700r4 in myself, took the driveshaft to a shop and had it shortened.. had the 700r4 rebuilt with lots of go fast goodies, including removal and reinstallation and 2400 rpm stall converter for $1200 plus I think it cost me around $120 to have the driveshaft shortned. my trans got the usual upgrades, corvette servo, plus a heavy duty sun shell I think they're called, kevlar bands and a whole bunch of other stuff.. just a shame the guy couldn't take the time to clean the valve body out properlly. Quote Link to comment Share on other sites More sharing options...
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