Automatic transmission upgrade

[Bruce-4310TX]

The 700r4 is longer than a th350 ck out this link at phoenix transmission. its such a small amount that you probably have enough gap at the end of the slip yoke it wont bottom out but needs to be checked. A 700r4 can be built strong some of the parts from the th350 are used to make it stronger such as the fwd sprag. ive rebuilt many of these transmissions there good if done right get a core built after 1988-1989 most of the weak parts were fixed (replaced by GM) before this year you have to buy more HD parts to make it last get one where GM's done most of the work any year prior to 85 all main parts are weak. Also get one with a 'K' on the side of the case has about 23 lbs of more aluminum in them where it counts these are 4x4 cases and yes they work in 2wd just change the output shaft and tail housing. i am still surprised you have a th350 in a 1 ton never seen one. Send me a pm ive got tons of info on this tranny if you need any. And yes 3.73 gears are great for towing and mileage dont let any one kid you.





700R4 - TH-2004R - TH-350 - 4L80E - High Performance Transmission Products

 

[carpenter383]

Hmm, didn't know about the K on the side, I'll have to remember that!
I've rebuilt quite a few 700r4's too
A th350 low roller clutch may be interchangable with a 700r4 (never tried to swap them) but the 350 dosen't have a forward sprag, it has an intermediate (2nd gear) roller clutch, which is a 1 way clutch but not the same thing as a sprag.
I'd say the weakest link in a 700 is the 3/4 clutches, but extra clutches can be added for more holding capacity.
The 700's sunshell is prone to breaking, they make a "beast" sunshell that won't break.
'87 and later 700's have a 30 spline input shaft and a 10 vane pump, so look for one '87 or newer.
Vette servo's are cheap and help 2nd holding power alot.
You can put a 4l65e 5 pinion planet in a 700 and all kinds of other stuff too, but you gotta stop somewhere or you'll have more money in it than it woulda costed to install a 4l80e
You should be able to get a decently rebuilt 700r4 for about 7-800 bucks if you bring in a good core.

 

[Bruce-4310TX]

Oops sorry about the forward sprag didn't have my manual in front of me, yep most of the 4l60e upgraded parts will work in the 700 the mistake most folks make is they get on e-bay order a bunch of parts save a little money and get the imported stuff. Just wasted all that cash, if you do it buy GM or quality USA parts For almost the same money you can get better servos than the Vette stuff those parts are great but for heavy towing you need more holding power and the longer those clutches last. buying complete kits from say monster or phoenix transmission means quality parts and parts that work together Even a mild shift kit is a must for a stock 700 works and lasts so much better. 'K' case only way to go also if its got a raised rectangle area near LH side of bellhousing top sometimes the sticker is still there, that transmission was a GM factory rebuilt transmission at least the first time.

 

[Diamondpilot]

I still say its 30 years old and has worked this long. You can buy a lot of gas for the price of the swap so why do it? My luck would be I would get it all the way I wanted it then someone would side swipe me and total it out. I would get book value which would be about $750.

I would just change the fluid out and install a large cooler on it then drive it like I stole it.

Chris

 

[machmeter62]

I have to agree totally. It's a lot of money and effort that may end up as a big disappointment in the end.

I have looked every where, under the hood, glove box, and door plates, for a code that would tell the transmission code, since the one-tons came standard with the GM TH-400, not the existing TH-350, that may have some more tired components, subject to failure? That still troubles me to think it was a factory mistake, however, GM installed in the 80's the small bloc Chev engines in Olds, creating a massive recall then!?

I know, I will never recover the cost of the upgrade, but my decisions are now based on the "misery index factor"... of a failure in the "middle of nowhere!" The cost of a new vehicle isn't an option, and with a stronger rebuilt GM TH-400R4, my future travel failures should be reduced?

 

[carpenter383]

I have looked every where, under the hood, glove box, and door plates, for a code that would tell the transmission code, since the one-tons came standard with the GM TH-400, not the existing TH-350, that may have some more tired components, subject to failure? That still troubles me to think it was a factory mistake, however, GM installed in the 80's the small bloc Chev engines in Olds, creating a massive recall then!?

I know, I will never recover the cost of the upgrade, but my decisions are now based on the "misery index factor"... of a failure in the "middle of nowhere!" The cost of a new vehicle isn't an option, and with a stronger rebuilt GM TH-400R4, my future travel failures should be reduced?

If you're mostly just worried about being stranded somewhere, and you feel like your th350 is on it's last leg, why not just have the th350 rebuilt? That would be the cheapest way to a reliable trans. You should be able to find someone to rebuild a th350 for around $350-$400 parts and labor. That's not counting R and R of the trans.

 

[machmeter62]

If you're mostly just worried about being stranded somewhere, and you feel like your th350 is on it's last leg, why not just have the th350 rebuilt? That would be the cheapest way to a reliable trans. You should be able to find someone to rebuild a th350 for around $350-$400 parts and labor. That's not counting R and R of the trans.

I had it rebuilt, after if failed from my abuse of exceeding it's limits towing. I can't remember the cost, since it was two decades ago now. My concern, it was too small for the job to begin with, since, according to all replies, the tranny was the wrong one installed at the factory. It was suppose to have the GM TH-400 in '78!

 

[machmeter62]

Let's look at the situation here. First you had the trans rebuilt after it failed due to abuse and towing. Then you say that you no longer tow with it. OK, the problem or cause is gone. You never did state if it was a high cube model which I think it must be. That being the case, too much frontal area to be thinking of overdrives and 3.55 axles. That really leaves you with a rebuild, maybe a heavier cooler, temp gauge and trans shift kit. The trans could have a heavier rebuild too. It's really the best option, and the wife can drive it normally and she doesn't have to find the unmarked OD on any transplanted transmission.



I think the RPO code is MX2 for what you have. If you have a list of the RPO codes, it will be a 3 letter option starting with M. No, it probably isn't a mistake. A few TH350's do end up in 1 ton models. It typically happens do to parts shortages. The TH350 ends up being mated to the small blocks and the lower GVW models of the 1 ton line.

The trouble with the Chevy small blocks being in the Olds and others was that GM never mentioned the situation to the owners. A lawsuit developed where the owners complained that they have purchased a higher class of car, but got the lower class engine. No mechanical problems were involved. The switch in engines was due to something that might be called a corporate wide item having to do with some governmental corporate breakup policies. It's a rather detailed item to explain here.

FYI as you've heard, the early 700R4s were rather poor. They were rushed into production with very little testing. Also, the TH400 is often overrated by the general public. Fix your TH350 and be happy.

In my first post, I mentioned that my GM Th-350 was mated to the 400 CID Chev. small bloc that had siamesed cylinders. I was told then, they were unpopular because of lack of cooling between cylinders, and only steam-holes? Did that bloc have a short production run too? I know that bloc is still in demand! Well, I guess the turn around of that bloc became very popular because of the high HP it could produce with any internal (bloc- twist!)

I assume that GM TH-350 never met a 454 in production then, of the one ton's? Thanx also, I will look for the MX2 code. This learning curve has been great! The GVW of my one-ton is 9000#, with coil-springs on the front wheels.