A DIRECT SWAP '71 904 for '70 904 plus... ???

-
3

3LOWmileV's

3LOWmileV's
Joined
Dec 20, 2006
Messages
17
Reaction score
0
Location
Charleston, WV
Hi, I am getting ready to swap on my 1969 Valiant 100 2-door post with original 170 Slant six the currently installed Automatic 904 (part # 3515804 ALUMINUM bell housing out of a 1971, what car exactly I don't know, also has "0744" on bell housing) for a very low mile Automatic 904 transmission from a 1970 Valiant 4-door which is also a slant six but the 225 size (it is the original transmission in that car but haven't gotten the part numbers off it). Will the 1970 auto 904 bolt right up without anything additional being done after pulling the 1971 auto 904 currently installed? Any bell housing or internal parts issues with the new transmission being from a 225 slant? Any benefit to keeping the current lighter aluminum bell housing (weight)? I am wanting to swap the transmissions as I don't know the history/mileage of the current 904, the new one will only have 10K gentle miles on it AND I will already be swaping out the driveshaft and 8 3/4" sure grip raer from the low mileage car to my 1969 so think I should just do it all at the same time. Can anyone also confirm that the driveshaft & 8 3/4 " sure grip will bolt right up without any modifications from the 1970? The 1969 has some smaller non- sure grip rear in it currently which is date coded 11/5/70, so I think it probably came out of the same car as the current transmission in it. Seems to me that if the new transmission bolts right up that the new driveshaft & rear should also bolt right up - all from the same donor car so driveshaft length will be correct? Sorry for so many details but want to be SURE & give enough info to you tech wizzards. Paul Charleston, WV
 
The two 904 tranny's should be just a straight swap. If you put the 8.75" rear end in there, you'll need to shorten the driveshaft approximately 2.25" to compensate for the difference in the depth of the two rear ends - ie, the 8.75" pinion will be further forward than your current 7.25" (?). You will probably need to change the U-joint end on the driveshaft to fit the 8.75" pinion joint, and, the spring mounting plates will need to be changed to the 3" size for the 8.75" rear, as well as new / larger U bolts to go over the axle and into the mounting plates.
 
Thanks OLDVART, I understand your info but I am also taking the driveshaft from the 8 3/4" rear & can use whatever spring parts I need from the 8 3/4" car, SO the driveshaft from the 8 3/4" car will already be shorter & won't need to be shortened as it is already, RIGHT? THANKS AGAIN for sharing your experience with me. Paul
 
Being they are both Valiants and one is a '69 and one is a '70 even though the '70 is a 4 door it has the same wheelbase as the '69 2 door so the driveline will work for your swap.

Chuck
 
If you are swapping the rear axles and are taking the springs as well, and dont intend to do any cleaning or painting - leave the springs and axle bolted together and remove them as a unit from the donor vehicle, remove the 7 1/4 with its springs and hangers brake lines etc from your car and swap them as a unit.

You save the time it takes to remove and install the U bolts (a pain) and the cost of the items as well. Its normal to replace the axle U bolts once they are removed since the threads and nuts get messed up taking them apart.

The leaf spring hangers are bolted in from the front on each side with 4 nuts inside the torque boxes and two bolts each side on the rear shackle frame brackets. Undo the rubber brake line from the frame and the emergency brake cables from their "U" clips, and undo the lower shock mounts and move them up and away. Bingo......wheel it over to your car and reverse the procedure - done.
 
You must log in or register to reply here.
-

Back
Top