have replaced my t400 with a 700r4 couple years ago but rear ratio is wrong now.
so going to swap over my differential from 3:08 to a 3:55 ratio.
rather than having the vette in pieces whilst it was rebuilt, i am buying a complete unit.

so what are the things to look for in doing the swap?
how hard of a job is it to do either on a hoist or using a pit?
is there a procedure to follow?
do i need to have the rear re-aligned afterwards?

any help/articles would be great.

and before you ask why don't i just swap the ratio in my original, i'm from ɹǝpunuʍop and parts take a while to ship/freight here.
so i don't want the vette taking up shed/hoist space whilst i wait for parts or a rebuild to happen.
that way if i ever sell the car, the next owner can put the original t400 and diff back if they want.

 

I would contact Bowtie overdrives...because the last Corvette I installed a 700R4 transmission in...required me to put a 3.73 ratio in it. Just sayin'. If you want to ask the owner on how well it works....contact 1974CorvetteJimCr here on the forum.

I personally with either raise the rear of the car with a floor jack or use my lift to only raise the rear of the car when I take out and install the rear differentials.

I take the differential out with the half shafts attached to it. I also leave the drive shaft attached...and with the rear of the car being higher...no transmission fluid comes pouring out.

Care must be taken when removing the rear leaf spring...and ESPECIALLY when you go and re-install it...or your can break an ear off your rear end cover. I generally loosen the four bolts for the rear leaf spring...while the car is on the ground!!!! and then un-cage it at each trailing arm. This will allow the spring to decompress. BUT...make sure you DO NOT loosen up these four bolts too much. To remove the outer long bolts for your rear spring ...with it up in the air...I place a safety stand under it near the bolt...lower the car until I see the bolt can move...thus NO PRESSURE on it. I take off the nut and raise the car so I can remove my jack stand. Then do the other side. Then when both sides have had the bolts released.. I begin to slowly loosen the four center bolts and I do them somewhat evenly. Then remove the spring.

Then I use the lower shock mount tool to remove the lower shock mount bolt that goes through your strut rod. more than likely the splines on it are wiped out and it may need to be replaced also. Remove the strut rod bracket that is bolted to the underside of your differential if you want to but it is not required.

Then remove the bolts and nut for your front differential mount bushing area and it may also may need to be replaced.

Then remove the two bolts for the crossmember for the differential. Then thread them back in about two or three threads...then using a long pry bar you will have to break the seal that the bushing that are in the crossmember as to the frame area...so you go between the crossmember and the frame and pry down on the crossmemeber... so it can drop that little bit/ when it has been released. Support the differential and then take these two bolts out and the differential will now be able to be lowered and slid back with the driveshaft attached ( and yoke also).

AS for spare tire carrier and exhaust...without knowing what you have going on there..I am tired of typing and do not want to type stuff that does not apply because I can not see what you have.

DUB

 

I m in agreement with Dub, I tried different ratios with my 700r4... 3.73 is the way to go.

 

I have found a complete rear in 3:55 ratio, v good condition, reliable source.
Has taken nearly a year to even find this unit, and that's going to cost me $1600Au (about $1230 Us)
There hard to find down here, importing one is out of the question due to weight.
We just karnt go to the corner store to get parts, have to order from over there, can take weeks for even a simple part.
I put the 4 speed/overdrive in to give better fuel economy,
Unfortunately with the 3:08's it lugs when you boot it, even dropping back a gear.
Going to 3:73's, to me, just seem to be counter productive, negating the benefit of the 4 speed/OD.
Anything would have to be better than 3:08, and the 3:55 seem the best comprise.

 

If you already located one, then by all means do whats best for you.. I was just giving my opinion on how it performs with different ratios.. I went from 2.87 to a 3.31 to a 3.73 .... 3.73 was the ideal ratio for me.. Several others I know went 3.73 with the 700r4 swap, on my recommendation, and are very happy.. good luck.. it must suck living there and being unable to get parts readily ... but I hear your beaches are awesome!

 

Well I assume you did not contact who I mentioned you to PM here on the forum and ask Jim about what kind of performance and fuel economy he gets out of his 400 CID small block....and also asking Bowtie Overdrives their views....but that does not matter honestly due to your circumstances. You have to use what you can get your hands on.

All I cans say...is I hope you have your Throttle Valve (TV) cable adjusted correctly. I know when I installed Jims 700R4...it took me a while to get all of what Bowtie Overdrives wanted to do what they wanted when it was tested with the pressure gauge.

Hopefully the gear ratio set-up you plan to go with does what you want it to do.

DUB

 

I had a 3.08 rear when I first changed to the 2004R, later I changed to the 3.55, it is a good combo.