Topic: 403 with 700r4?

[ronnie]

ive got a 403olds in my 79TA, its been built and the engine dyno showed the following... 500ftlbs @2900rpm and 396hp @5000rpm. im running a 400 tranny with 2500stall and a 3.42 rear end.

im considering going to a built 700r4 (with 3500 stall) and 4.10 gears. the reason i want to do this is more get-up and go. the overdrive with 4.10s should give me around the same cruising rpms as with the 400 and 3.42s but i should have much better acceleration with the numerically higher gears in the 700r4 and of course, 4.10s. also, i believe that my engine can safely handle the bigger jumps in rpm from one gear to another. with all that torque i shouldnt have a problem falling out of powerband.

am i wrong? is this a bad move? anyone ever done something like this before? what do i have to do to make the 700r4  bolt to my 403?

[brian c]

Well you'll need an adapter plate to bolt the BOP engine to a Chevy tranny. Then you'll need to shorten the driveshaft. Then you'll need to fiddle with the tranny cross member.

For what you're doing, why not consider a 200R4 instead? It won't need the adapter plate and can be built to handle the HP and torque of your engine. Its more of a drop in than the 700R4.

[ronnie]

hmm, 200r4? i hadnt considered it because i know nothing about this tranny, i will search for info. the reason i like the idea of the 700 is that i know a guy who builds them and installs them for a suprisingly low rate. a friend of mine had one put in his 81 z28 for about $1700. (3500 stall, electronic lock up)

am i right thinking that this swap will give me more performance?

[brian c]

The 200R4 came in Monte's and Buick GN's - to name a couple. They're shorter than the 700R4 which is also a good thing.

Performance wise...well you'll get a lower 1st gear and get OD out of the deal so you're gas mileage will improve on the highway. That's the whole thing driving my conversion once I get the tranny built to handle my 469

[ronnie]

after doin some brief research i may stick with the 700, its 1st and 2ng gear ratios are numerically higher than the 200 offering more exceleration. im also considering building another engine in the future, im not sure if it will be a SBC or stick with the olds. if i do go with a small block i may as well use the 700.

[defend21]

Just curious, what did you do to your 403 above factory to get those numbers?  I did the 403 rocket buildup but have no idea how it improved hp.  It's still a dog with the TH350 and factory rear.

[Wallington]

1st and 2ng gear ratios are numerically higher than the 200 offering more exceleration.

Exactly the opposite of why you'd want it. It's too short geared for a low-rpm high-torque engine. 10 year old post but has possibly bad information in it.