The Stovebolt Site Forums The Shop Area General Truck Talk 700r4 tranny---good or bad

Does anyone have any experience with the 700r4 tranny? I am considering putting one in my 70 3/4 ton hooked up to a sm blk 350. I will be using the truck to tow my boat, as well as regular driver and like the overdrive for gas mileage. I currently have a manual in it. I know I need to get an adaptor for the transfer case. Does the tranny have a good rep--or would I be better off going with a th350--400. If so why?

I have bought a rebuilt one to put in my 72 behind a 230 6. As I understand it, the better 700r4s are made after 86. 87 and up have a number of improvements that made them good transmissions.

You can look up bowtie overdrives and they sell a switch kit to lock up the torque converter. This reduces tranny temps as there is no goo friction from the torque converter once the tc locks up.

If I had my choice, to put in a 3/4 ton tow vehicle, I would go for a 4L80. The 700's just don't have the beef for continuous heavy work.

A TH400 would be alot stronger that a 700R4 but no overdrive. 700R4's dont like alot of torque. I would go with a 200R4. They seem to hold up alot better and theres no electronics like in the 4L60 or the 4L80.

Oh yeah...Im on the 3rd "built" 700R4 in my GMC Syclone. Torque = Kaboom.

If you think the OD will get you much more MPG's, you're wishful thinking. It will get you more speed, but unless you drive it constantly, it won't pay for itself in fuel savings. Go with the durable TH350 or TH400 for a working truck.
Just my opinion,
Scott

If you get a late 80's one and not one of the mid 80's ones it would be better. Personally I have had two th-400's and they are awesome, but they are not sweet on the highway. The 700-R4 has a bad rap, and some of it is probably deserved but I think for a recreational tow rig it would work fine. You could also try new rear end gears and a th-400. Good Luck.

Kyle

Sounds like the th400 may be my best bet with higher gears in the rear. Right now I'm running the stock 4:10's. I'm still trying to figure out the cost involved in this. At least 400 is more readily available and I may be able to find one with all the attachments from a mid 70's truck. Thanks for all the input. Has anyone done this conversion from a manuel to a th400?

I think the 700-4R is the greatest trany out there. I had one in a 63 with 454 & it worked great. Idled down the road 1800 rpm at 70 mph. I,ve got one in my 70 stepside with 350. It goes into o-drive & the converter locks up you can,t hear the engine running.

I agree with Wrenchbender, I have a 700R4 behind a zz4 350 with over 400ft. pounds of torque, runs great. Reduced the rpm's on the highway alot. Running 373 gears. Made the same switch in the 72 Nova we owned, same results. Would never go back to the th350 or 400. Worth the extra bucks. Gas mileage did improve, but more importantly the rpm's were reduced , less engine wear. Just my thoughts, has been a good move for me.

I would go with a 4L80. Its not about fuel milege but being able to haul something with lower rpms so its easier on your engine. That trans is strong and durable enough in the long run all new heavy duty chevy trucks run them. Thats why you dont see 350s or 400s because the 4L60s and 4L80s replaced them. As far as the electrical harness part you can get aftermarket from Summit Racing and its not that hard to hookup to your existing harness.

http://www.bowtieoverdrives.com

... is one place to poke around and look at information and tech articles, I've seen it mentioned in many posts about swapping in a 700r4.

Some other places to poke around:

http://woogeroo.home.mindspring.com/autolinks/transmission.html

-W

rocket - the 400 was available in 70's trucks. I had a 76 with 400ci and th400, that thing was solid. The swap would be really easy, it would also be easy to swap in the 700r4. The swap will not be overly difficult, might have to find or fab a new crossmember? You will also have to get your rear driveline re-sixed. Is this a 4x4 or 2x4? If it is a 4x4 then there will be more to move around. Good Luck.

Kyle

Hog,

I currently have two Chevy trucks equipped with the 700R4 tranny. They have both been reworked by a tranny shop and they work perfectly. A 700R4 can be beefed up to take even a big-block, but it needs to be built by a pro. I fabbed up a floor-shift for my '59 Apache and it works fine, but you can also get a Lokar floor shifter. It's the only way to go while using 3.90 or 4.11 rear axles. The low gear, as I recall, is 3.05 to 1 and the O/D is 30% reduction. Do the math.

http://www.tciauto.com/tech_info/trans_dims.htm

more info... jsut stmbled across the site link again right after looking at this thread.

-W

I have an 89 model 700r4 in my 85 3/4 ton suburban with a small block 400 and 3.73 rear. I tow a 8600 pound boat with it and never have a problem, I even tow in OD which everyone says not too, but the 400 just hums along without so much as a hickup. It has been built with some aftermarket goodies, but nothing expensive. I think part of using the 700r4 is having enough torque and rear gear that you don't keep locking and unlocking at lower rpms without having so much torque that you munch the thing.

Thanks for all the info--Coachfrank and Apache kid, do you do much towing with your truck? That's my main concern is being able to tow my boat up and down hills without issues. Boat weighs about 5500 lbs. Truck is 3/4 ton 4x4. Rearend gears are 4:10's behind stock 1970 350 sm blk. 4.3in84toy, do you do a lot of hills or mostly flat?
The 700r4 would definetely be a cheaper conversion than the 4l80--no elctronics and I believe easier to come by. Any comments? Thanks, Matt

Not a bunch of hills. Certainly not any long ones down here. Whenever I think I might downshift, I manually shift out of overdrive instead of possibly lugging with a big load behind me. Then I just pop it back in OD on the way down.

I also had a 97 suburban 3/4 ton with a vortec 5.7 the 4l80 and 4.10 gears. I still used the 85 suburbanto haul the boat, but I think that is because the 400 small block is a towing masterpiece (if you have a giant radiator).

With your stock 350 and short 4.10 rear gears, I think the 700r4 would be acceptable. You would need to have it built with quality parts. The turbo 400 will be bullet proof in your application. You could change to 3.42 gears, but that would add some expense. None of these ideas are real cheap.

Before purchasing the suburban I used an 87 1/2 ton 4x4 with a 305 sbc, 3.08 gears and a turbo 400. It didn't like the hills too much, but it pulled my boat just fine.

Do you just want to get rid of your SM465? Ever thought of a gear splitter? The concept is similar to that of a 2 speed rear, when you begine to climb the hill, you shift into 3rd high (4 low) allowing you to maintain stay in your power band without revving too high.

I want to get rid of the manuel manly because we use the boat a lot and the wife can't do the 3 pedals with 2 feet dance coming out of the ramp. I would also like to get the overdrive on it because we will be using it on 4-5 hour road trips.
I checked into a couple of gear splitter units. They are definetely a cool set--but pretty spendy. especially nice if you have a wide ratio gap between gears. I guess I'll be on the lookout for a 700r4 out of a junker. Maybe I'll even get lucky and find one hooked up to a 205 case, which would save me a few hundred for the adaptor. M

Have you looked at the Ranger Torque Splitter from Advance Adapters? It goes in front of your SM465 and moves the shifter back 7 inches. It sould be the easiest way for you to get overdrive and then be able to split gears on the hills. Less than $1500 and you'll only have to shorten a drive shaft and cut two holes in the floor.

I understand your siutation completely, I owned a boat rental business and there was lots of time spent teaching the employees how to handle our "delivery" truck which was a manual trans 4x4.

With your transmission in granny low and your transfer case in 4 low, you should just be able to creep out of the ramp. Literally just take your foot off the clutch with greater than a 50:1 crawl ratio.

I hate to say it, but you might be better off selling your truck and buying one with everything you require already in it, cause the conversion just won't be cheap.