Clearance issues 400 small block and 700r4 transmission

[rayray767]

Front driveshaft is almost butting up next to my transmission pan you can barely get a fishing string between them but it does turn freely. I tried reversing the driveshaft it doesn't bolt up right. I was told I could change out the yolks but the front and rear don't interchange. I had bought a new aluminum transmission pan it's even thicker and won't work at all. Any ideas I'm frustrated.

[warbucket]

I think you can get a driveshaft made with a smaller CV joint or some guys dent the pan in for clearance.

[rayray767]

Yeah I had open up the pan to check clearance before denting in my pan and there's no clearance to do so. If it had been the 350 tranny it would've had the clearance to Dent it in the pan. Thanks for your comment war bucket . I'll have to check about that CV joint.
Surely there's someone out there with the 400 small block and a 700R4 transmission I can't be the only one out there. :p

[DeadheadNM]

Not sure I can offer much help but I did a 700R4 install in my 72 K20, which has the correct 350 motor and NP205 t-case. FWIW - I do not believe there's a clearance issue in the K20. GM did use a "K" case 700R4 for 4wd applications. Maybe these used a pan that afforded more clearance?

[rayray767]

It's the 400 motor is whats giving me the clearance issue if it had been the 350 motor I was told all would of came together good with the 700r4. (UPDATE) ... So now I find out after putting my 4 inch lift on the truck I find out that the money I spent getting my shafts shorten and lengthen is out the window now because both will have to be made due to the spline is about 3/4 out. Needless to say that was about 250.00 bucks out the window !

[1rippen6]

I could be wrong but the 400 as far as length or width should be no different than a 350. You should be able to pull a 400 out and install a 305,307,327, and on and on and use the same motor mount and transmission. Even BB will work I installed a 454 in my 71 and used the same motor mounts and transmission. I know they have BB specific motor mounts but the small blocks will work. I think you issue lies in the 700r4.

[kwmech]

I've done 3 or 4 of these for friends and customers. It has nothing to do with the 400 engine. The 700 pan is wider in the back than either the th350 or the th400. Just mark where the drive line is going to rub with a marking pen and remove the drive shaft. With a smallish ball peen hammer massage the pan inward to give yourself some clearance. You don't need a huge amount as the joint is solid at the case, just enough so it doesn't rub on the pan and you can get maybe the tip of your pinkie finger in there. Don't forget that the valve body inside that pan is fairly large, but you can massage in at least 3/16 of an inch. Good luck

[rayray767]

Thanks for your info . When they took off the pan the showed me there was a resister or valve body or what ever you call the piece that almost up against the pan wall. I Was told you can't hammer that in or cut. They told me that the 350 tranmission when you open it up that there was clearance in that corner. I guess I will try to get a photo with the pan off and then you can tell me if I can still make it work . I'm no transmission guy for sure so I'm going on what there telling me and showing me. I don't know if this helps but the transmission is the year 87 up.

[rayray767]

Saw this on google images

[DeadheadNM]

To make use of the 700R4 you either move the engine/mounts forward ~1.75" or shorten the drive shafts. Which did you do? I moved the mounts forward and kept the drive shafts stock.

[rayray767]

I had the drive shaft shorten so I guess I need to buy all new shafts and make them custom $ this really sucks for me. The good weather is back and I'm not able to drive my blaze I don't know how long it take to get it right. I'm left with about 16 weekend days left to drive it. I spent a boatload on that 400 Block last year and I think I put 1 miles on it all my cash is invested in this Blazer and I can't even enjoy it.... Sad days for me . Thanks for everyone's comments I do appreciate them. I will be becoming a premium member shortly as this site has helped me so much and I have a lot of miscellaneous Blazer parts help out need.

[rayray767]

The members in need of them. Sorry voice control don't always work correctly

[DeadheadNM]

If you really need to go with new shafts you may want to look into moving the engine forward, which may help with your tranny clearance issue and give you more space between the firewall for an HEI. Good luck.

[rayray767]

I'm definitely going to look into that thanks .....

[Chulisohombre]

I don't see but did you use the stock 205 or the transfer case that came out with the 700? If its the 208 I'm guessing you can get a clicking ring and move the driveshaft out with a turn of the transfer case pissible.

[rayray767]

Still the stock 205

[Chulisohombre]

Ok so it's a fixed location off the adapter. If there is still some room between you could be ok. You can grind a little bit off the ears on the yoke and driveshaft to clearance a bit too. I think the 700 is 3 inches wider pan than stock 350. The 400 engine is still a small block and will sit in the same place as stock. As was said even a big block isn't the difference. You can move the engine forward two inches with the 6 cylinder mounting holes on the frame. You would also then possibly have interference with the radiator at that point though. I've seen where a lot of people will then put in electric cooling fans in that case. And also will need rework of the driveshafts though. It will angle the driveshaft back at a stock angle but I'm guessing the yolk on the transfer case will still be just as close to the transmission though.