so the TH350 will not adapt to my 700R4 in my 88 chev ?

The length is different and the output splines will not match either. It is not a bolt in. It is stil easier and better to use a 700R4. Find cause of problem because the 700R4 is not a bad tranny. If you are have problems with a 700R4 is is because of how you are using it (gearing and usage) and cooling it, not because it is defective design. Unless you resolve these issue the problem with return even with a THM 350. Also as some lese stated, the wil be a performace drp with a THM 350 because first gear is about 22% taller than 700R4's. Second gear is about 7% taller too.

----------------- TheSnoMan.com

I had a new 83 Chev 1/2 ton with the 700R4.....compared to every other tranny I had experience with, it was godawful in terms of smoothness, driveability and durability. Someone on this group said a while back that GM did a major redesign on the 700R4 in the mid to late 80's which made it more durable and driveable.....which was just peachy for the suckers like me and thousands of others who were stuck with the first 5 years worth of garbage. Died after four years of light, non-off road, non-trailering use. Back in '87, they wanted some obscene amount to rebuild it. I replaced it with a TH350 with a lockup converter, switched the driveshaft, and that truck went another 10 years and 200,000 miles without a hitch. It was an easy switch. I was told the TH400 was doable but more of a pain to. This was on an '83 mind you, so FWIW.

On Sat, 9 Jun 2007 10:06:38 -0400, "Chevrolet" wrote:

Most 700R4 that I have seen toast is because they are in older 4x4's with big tires and stock gearing which play heck on tranny. There is a mindset with some that you do not need to install taller deeper axle gears and the tranny does a slow burn. ALso some try to tow with 700R4 in OD which is not good either. The tranny has a .7 OD so even with stock tires and a GU6/3.42 axle ratio the tranny will tend to unlock a lot in OD and ride converter for a while before downshifting from fourth to third. At 65 MPH with this combo you are turning about 1800 RPM in forth/OD. When converter unlocks because of load on it the coverter is slipping and building heat to try to make the extra 30% more torque just to cruise and it does a slow burn. Throw in oversized tires and it is even worse. Realistically you want at least a 3.73 (GT4) with stock tires in a big 4x4 and better yet a GT5/4.10 which which you would have about a ideal match for power and cruise with a

700R4 in a big 4x4. If you are running a lift and big tires figure on a 4.56 or 4.88 or even more depending on tires size becuase there is no perfect axle ratio for all apps as it depends on tires sizes. You do not have to mud to toast a tranny with tall gears and big tires. People think it does not matter and blame tranny not what they are doing with it. Go ahead, go back in time with a older tranny and only three gears and more limited performance potenail due to redcued gear ratio options or take the time to rethink this and study your axle ratios and maybe regear them and/or add a aux tranny cooler because stock cooler does not cut it sometimes and heat from tall gears and big tires cause tranny to run on converter stall a lot is the 700R4's number one enemy with maybe shift kits being its second biggest enemy. Actaully the 700R4 kinda keeps the myth alive about deeper gears are not needed with bigger tires in that it has a much deeper first gear and starts a tall combo better than a THM 350 or 400. Many still believe that the taller the axle ratios the better the MPG in a big truck (they think that a 3.43 or 3.73 is great with big tires and that even a 4.10 is all the gerar you need with any tire size) but the problem is that it still takes the same HP to move the load and the taller the axle ratio the harder the tranny and engine has to work to make the needed power. There is one knuckle head around these news groups that has tall gears and big tires on a 4x4 and cannot use 5th gear on his 5 speed and goes so far as to say that is just fine or normal whithout even thinking that there is power lost in the remaining four gears as well. (They figure that is what low rang it for even though that is not what it was designed for)

----------------- TheSnoMan.com

On Sat, 09 Jun 2007 14:57:19 GMT, "Augustus" wrote:

The 700R4 was troublesome from 81 thru 84 (easily spotted by 27 spline input shafts) For some strange reason, GM decided to bypass the cooling of fluid in upper gears when it came out. My guess is they figured that with converter locked there would be not much heat and it would save a little power/MPG by not pumping the fluid to cooler. They fixed this a few years later and by 85 they redisgn a lot in tranny based on in service failures and the 30 spline unit have these revisions. Also as stated earlier, ANY 700R4 can easily be upgraded to the latest revision on rebuild so you can make a solid 700R4 even out of a 81 version. THey started with the THM 350 and modified it and the gear ratios and added a OD to it too and it took a few years to get all the bugs out of it. GM is not alone in have problems with new tranny designs and the 700R4 was a major shift in tranny design and application. When they converter the THM 400 to the 4L80 they basically left gear case intack and retained existing gear ratios and added a OD section to it with some electronic controls as well and since GM had some track experiance with the 700R4 by then and basic tranny was not altered much other than as earlier stated the 4L80 was not trouble prone from start. Nothing wrong with 85 on 700R4's and they were last tweaked a minor amount on shift quality in 87 and left unchanged until the 4L60 came out around 92. The 4L60 and 700R4 share internal parts with only the valve bodies being different (700R4 manual/hyd and 4L60 is electronicaly controlled) Proper used and cared for the 700R4 is one of the better trannies GM built and its effective gear ratio range from first to OD of 4.37 to 1 is superior to the THM

400's 2.48 or THM 350's 2.52 range as it allows for the usage of even deeper axle ratios for even more power yet lower cruising RPM too. (you can run a 4.56 with a 700R4 and have a noticably lower cruisng RPM than a THM 350 or 400 with a 3.73 and a LOT more power in the lower gears too. The mistake is to use a 700R4 AND tall gearing.

----------------- TheSnoMan.com

I want to add one more thing. There is two kinds of 700R4 cases out there and the ones meant for 4x4 have a case that is about 30 to 40% stronger to handle counter torque from Tcase bolted to it in HD servvice. You could find them both ways though in standard and HD cases in a 4x4's. The really easy way to tell them apart is that the HD case has a casted bolt on lower torque conveter cover while the standard case has a stamped metal one.

----------------- TheSnoMan.com

had a 700 in my 87 K5 with a 6" lift and 35's regeared to 4.56 and never had any problems at all. just gotta know how to drive it. sure if your mudding or rock crawling the 350 would be a "better" choice. but for a DD i'd stick with the 700. or if you want drop an atlas in the damn thing.

I would still say 700R4 is better for off road because of 22% deeper first gear which is a BIG plus moreso off road than on it. I image that your 4.56's played fairly well with your setup.

----------------- TheSnoMan.com

yeah that and one hell of a tranny cooler...

This is not a good thing, you can over cool oil and a big cooler over cooling actual restrict cooling flow because cooler thicker fluid is harder to pump. Even a bbig cooler is not going to save you if you have the wrong axle gears for what you are doing.

----------------- TheSnoMan.com