Captain bob

pulling my hair out on this trans swap.1971 corvette removed turbo 400 and installed 700R4 bolted up bell housing ,installed convertor,filler tube,for some reason em brake cable wheel no problem .the trans tailshaft center in tunnel and bolted to trans cross member bolt holes (OEM holes) it becomes way out of alignment with centerline of rear differentials ,the driveshaft would be way out of whack. i made centerline exact and tailshaft is against passenger side F/G in tunnel i am sure driveshaft yoke will hit F/G tunnel.has anybody ran into this problem.i went thru the extra expence installing 82 chevy caprice tail piece on trans to make rear mount fall in OEM trans crossmember and it does over original holes.--------HELP

Captain bob

has anybody had to cut clearance in passenger side of shaft tunnel fiberglass to clear driveshaft yoke??? i don`t remember anybody mentioning this on there trans swap.

bluedawg

I had to pry on the tail shaft some with the cross member bolts loose to keep mine from rubbing. I used the gforce cross member.

rickslt4

I got my cross member from Bowtie Overdrives, bolted right up.

Captain bob

past forum sugestions were to purchase new cross member to take in to account the 700R4 is 3" longer on cross member mounting block of trans,or change tail piece to 1982 caprice full size car which is 3" shorter and allows you to use OEM. turbo 400 cross member.i put a lot of time and effort into this trans with a CNC built billet machine pump.now i brought car to my friends shop to install trans utilizing a lift.a easy job right well the bolt holes in crossmember line up nicely in center of F/G tunnel but if you pull a string from centerline of trans yoke (no driveshaft) and centerline of yoke in differential the trans is off 1 1/2" .i am sure the short drivshaft could never take this miss alighment for long. a attempt at perfect alignment would require me to cut out F/G out of drivers side of tunnel around trans yoke.what gives! did you guys just just install and disregard acute misalignment and hope for the best??? those of you whom try to help used a non stock cross member and stock transmission tailshaft.this might change alignment factor don`t know.

mikem350

I would loosen up all the mounting bolts, and try shifting the trans over with a big pry bar. Then tighten. See post #3 above.

Possibly even loosen the motor mounts at the same time. But, make sure of fan clearance when you are done!

lionelhutz

The driveshaft has to be misaligned in one direction or the u-joints would go bad. The misalignment allows the cups to rotate keeping the grease moving and the needle bearings from just sitting and wearing in one spot.

mrvette

FI on a 355 engine, used to be a 4 speed car, put in a 700 for the OD, and have a 336 rear.....kept same cross member by cutting it out on each side, and welding 2" L angle steel to the top/back and bottom and a large bolt going fore/aft so the center can slide back when released, but kept the same mount as the Muncie, that 'shoe' that bolts to the trans/cross member....still had to cut the floorboard on the pass side to clear the trans 2" away....

I found the 700 was ok for the OD, but in normal traffic, the Trans Go shift kit had it slamming into second before I cross the street from a light, bogging the engine......went to the 200 4r and cured that problem, the 200 is a much better match, and would still have had to move the floorboard/tunnel.....another thing, the 700 requires a shortened driveshaft...at least mine did,.....the 200 does not.....

Captain bob

thank thats what i wanted to hear. i am not the only guy in the world that has to cut floor board or actually F/G tunnel on passenger side of car.i have seen a "jackshaft" that the name of a drive shaft on a boat run at a radical angle but that was limited to 2500 rpm, this car goes to 7000 rpm in third gear that shaft is spinning mighty fast at that angle!

lionelhutz

The most important thing is to keep the transmission output shaft and pinion gear shaft parallel to each other. When you shove the rear of the transmission over don't you end up with the engine/transmission crooked in the car?

Isn't the pinion offset to the passenger side of the differential housing? Any engine/transmission centered in the chassis won't line-up to the pinion.

What would the angle of the shaft be?

Captain bob

yes the pinion is offset in axle housing favoring passenger side.i can control out of alignment on the vertcal plane by shiming or decreasing transmission mount to crossmember connection,however the horizontal plane is way out of wack with the trans. tailshaft in center of tunnel.the spline end of yoke goes into trans and then a radical offset in universal joint to match trans yoke end of driveshaft to universal at differential end of driveshaft. just looking at it tells you there is a problem this will never work.forcing the engine/trans over with pry bar till front universal hits tunnel help considerably but just not right.axle has never been out of car and along with pumpkin is in perfect condition as well as spring mount,the problem is not there and worked perfect with turbo 400.

cv67

x2 they do have to have some offset so the ujoints can work the way they are supposed to.longer the trans is the more it will show

lionelhutz

I'm a little lost on how the TH400 sitting on the same mount could have lined up the driveshaft but the 700R4 doesn't?

How much angle would it put into the u-joints?

Captain bob

lionelhutz because i used the 82 caprice tainpiece the crossmember holes line up with the embossed holes in trans just like turbo 400 however the 700R4 is much longer going into tunnel . this would make the driveshaft angle much more pronounce because the driveshaft is making the same angle in a much shorter distance.cusinartvette pick right up on the problem together we can solve this.

lionelhutz

By my quick calculations the angle will change from about 3.1* to 3.4*, assuming your driveshaft started at 28" long which I think is the length of a TH350/TH400 shaft. I really don't see what the issue is with that small an angle since there are LOTS of RWD cars running straight axles with more angle than that.

Captain bob

i will measure with tail piece in center of tunnel and get back to you.also will push trans to passenger side just enough to prevent yoke from hitting tunnel og course this would entail redrilling cross member or welding adapter bracket.

lionelhutz

Don't forget that the 82 cars (and 81?) cars came with a 700R4. With the engine/transmission centered and the same differential offset, those cars would have come from the factory with the same angle that you'll end up with.

You also don't want different angles at each end. Having 3.4* at both ends is better than having say 1* and 2.5* at the ends. Anything more than about 1* to 1.5* difference in angles between the ends will start to cause vibrations. As I posted before, it's best to have the transmission and differential center lines parallel to each other compared to a configuration where the driveshaft appearing to be straighter but without the ends parallel to each other.

hugie82

I'm not sure why you are using parts from a caprice when you can use any 82 crossfire corvette as a template.

mardyn

Looking at my '73, it appears that the tail shaft housing on the Turbo 400 is slightly offset to the passenger side of the tunnel...

mardyn