Question about 700R tranny

[RicksTrucks]

1. Is it a direct replacement for a TH350? Same length so no need to change the drive shaft?

2. What would be a good price for one from a running 80's van? Would $195 be okay?

3. What would be a good ratio rear end for it behind a 350 motor? I have heard a 3.73 would work best.

[trukindud]

ive heard from my dad thats putting one in a 69 camero that there about 4 ich longer he said it would be good to rebild it well it is out cause you dont know how long the life it has left running dont mean much those gears would be awsome hope that is some help

[49m]

The 350 trans is not overdrive. the 700r is. The drive shaft would have to be remade. The 373 gear ratio is good but it will not get you good gas milage.

[cdowns]

if you have the original th350 with 6" tailshaft you need to shorten driveshaft// i only like doing a job once so i suggest getting it gone over and upgraded prior to installing

[Gray Ghost]

3.23's seem to be the best all around ratio for mileage and fun with the 700's deep first gear. Got a friend who has that combo in his El Camino and loves it. He gets 22 mpg when his foot is out of the firewall.

[68C15]

I just did the same swap in $700C10's truck 2 weeks ago. it came from an 89 astro and went in place of the TH350 9" tail shaft. we used the same drive shaft. I had to move the X-member back a little and drill new holes in the frame. i used the mount from the TH350 so I didnt have to drill new holes for the mount. (700R4s use a single stud while the 350s use a 2 studs mount) we gently bent the cooler lines to the slightly different place to mate with the 700. all in all it was a simple swap.

here is a list of the different trannies and their respective dimensions.
http://www.tciauto.com/Products/TechInfo/trans_dims.asp

I am getting ready to do the same for my truck. I think his has 3.08 gears. it moves quite nicely around town. I havent had a chance to take it on the highway yet. i will talk to him and see what he says about that.

[STP67-72]

I have done several 350 to 700's. The driveshaft will need to be shortened. You can move cross member and drill new holes in frame.The yoke will work but the 700 yoke is alittle longer. All of your shift linkage will also work. I have always run 373 gear.I have heard 308 does not work very good.I would say 342 or more.
Hope this helps.

[N2TRUX]

Good info Steve. You need to tell us more about what motor you are running, what tire size, and what is important to your personal needs. All of this will be important info to determine what gear ratio is good with a 700r4.

[chris71]

some years for the 700's are better than others, 82 was the first year, the first couple years are weaker, i think 86 and up are the stronger ones, dont get a 700 from a 6 cylinder car since the 6's have less clutches in them than v8's, the flexplate dustcover is the same between 700 and th350, you will need a 700 tv cable and dipstick tube, cant use the th350's. i had 3.73's in my truck when i had a 700 in her, i thought the combo was great, great off the line and good on the highway at 70 mph. you need to make sure your tv cable is adjusted properly, get this wrong tranny will blow in a matter of months, here are some links on the 700

http://www.purplesagetradingpost.com...o/700R4p1.html

http://www.transmissioncenter.net/700R4.htm

http://www.bowtieoverdrives.com/inde...FTgrOAodFU88Lw

[RicksTrucks]

Looks like it is from an 84 with a 350 motor. Would it be worth $175?

[Huck]

Rick, I would pass on that one. The better ones came in 88 &up. You will need to swap out the tailshaft to the older style for the manual speedo cable hookup. 308 gears on a 700r4 are a bit tall for most---with 373 or 354/342 being a bit more desireable.

[RicksTrucks]

Originally Posted by Huck

Rick, I would pass on that one. The better ones came in 88 &up. You will need to swap out the tailshaft to the older style for the manual speedo cable hookup. 308 gears on a 700r4 are a bit tall for most---with 373 or 354/342 being a bit more desireable.

Thanks

[70GMCer]

Originally Posted by RicksTrucks

Looks like it is from an 84 with a 350 motor. Would it be worth $175?

Some will disagree, but, if you know it's working right, use it. Just replace the 1/2 shift servo to a Corvette one and also change out the boost valve. These parts are easy to install. You will also need the lockup wiring for the converter. Then, you'll have a nice shifting tranny. Also, no need for a shift kit in these.

This is what I bought along with a new valve body plate. Again, this is assuming that you don't have a big HP motor in front of it.

http://www.bulkpart.com/Merchant2/me...roduct_Count=4

[hvychve]

Well, for some reason, I have heard that the shaft needs to be shortened and some say it dont, however, I Installed a 700r4 into my truck and it used to have the 350 ENGINE, it bolted right up, I even used the same linkage, I also used the shaft, I shorted my slip yoke travel a bit but wasnt enough for me to worry, the front part of the shaft is pretty much stationary, it slips at the rear, near the center support, I than installed a stock 402 big block and used the big block mounts and perches, this ended up shoving my engine and trans back even further, now there was room for concern, I was butted up against the tail shaft seal, I than took off my center support bracket and shimmed it with about 1/2 spacers, ( I am talking about the bracket that bolts to the crossmember that bolts to center support bearing, this shoved my front drive shaft a little more than 1" and more than enough clearance from my tail seal, I improvised slippage from the two shafts but nothing to worry about , the two shafts still have plenty of in and out movememnt, So I am not clear on which trucks need to have shafts shortened and which ones dont.
I ended up using a custom bow tie trans , its above stock and can take some seriuos poundage( so they say) I soon will be adding some horsepower components to the big block, I guess we will see, good luck .

[red71cheyenne]

The TH350's had different tail shaft lengths. On one, you'd have to change the drive shaft, on another you wouldn't. When I first swapped mine in, no change to the drive shaft was needed. I eventually went to a one piece shaft though, and thats the only reason I changed. Did have to move the cross member though, as all stated.

One big point I would make, is have the TV cable set by someone that knows how to do it. It'll make a difference in the life of the tranny. Hindsight it 20/20 on that one. Good luck!

[Pont406]

After you guys swapped to 700r4 do you still tow with it or majority of these swaps are for cruising only? I am starting to consider 700r4 also but I need to make sure that I still can tow with it, 5000 lbs max. Thanks.

[red71cheyenne]

I don't tow with mine, but I don't see why a beefed up '89 or newer one wouldn't handle it. If you went with a 4L60 or 4L80, you'd be even that much stronger. Just have to figure out the electronics on that.

Last time I had mine rebuilt(2nd time), the guy that did all the work, upgraded it to '92 and up standards. It has lasted longer than the others. The first one was an 87 that had to be rebuilt after only about 2000 miles. Once again, TV cable is really important.

[sickred72]

yes you need to have the drive shaft cut 2" exactly. the 700r4 you need to look for is 1987 up ( thats the aux.valve body ) factory updated. 373 gears are the best, your gas milage would be great! 700r4's have a super low 1st gear..........i know all this because im in the tranny business...i own a torque converter shop in portland oregon. you can keep the lockup function by buying a part made by painless performance or tci. or you can buy a dummy lockup converter ( which would be the easy way ) and it would make the tranny the same as a th350 but with an extra gear. =) (you have to tell who ever builds your tranny to make it non lockup) if you want to use the lockup it works off a vacuum line.......dont let anyone talk you into using a toggle switch to go into lockup! YOU WILL FORGET TO FLIP THE SWITCH AND BURN IT UP COASTING DOWN HILL!!!!!!=(

[mnunn454]

One thing not mentioned yet is an external tranny fluid cooler. Highly suggested because the later model trannys don't tolerate higher temps as well as the TH400/350/PG trannys do. Particularly relevant if you're going to tow anything.

[stope4]

If any highway driving, 3.73 gears or greater. Nothing less. With 3.08 gears my rpms were down in the 1400s when the vehicle shifted into overdrive. In other words, the power was terrible. Shorter drive shaft by about 3". You can use the existing linkage but it is a little off. My recomendation is you buy the linkage conversion kit. This will allow the linkage to line up. Do not expect to get 22 mpg. I'd say more like 16 is about right.

FWIW, this is my opinion only:
I did this conversion on my first truck. I wouldn't consider it on my existing truck. Don't get me wrong, I didn't have any problems with the transmission but there was a lot of tinkering to get it right. I had to deal with linkage, tv cable, driveshaft, yoke, rearend gears, lockup converter and the concern about towing for a few extra mpg. MPG is what it is. If you really need better gas mileage, I would think a used Honda would get you better bang for the buck.

[piecesparts]

On myt ruck and my son's truck, the exchange was not that hard. The trannys were the same length (truck 350s have a longer output shaft tube, than most car trannys) The differences included the change in a my rear mounting points on the cross member, the front yoke (can be purchased), the shifter indications (I changed over to floor shifters) and the kick down cable. The 700 R4 is a little different than a 350 in it's principal---it needs to be adjusted just right.

The price is USUALLY commensurate with the quality of what you are purchasing. For instance; $195.00 for a GOOD 700 R4 is a rarity at best. My guess would be BEWARE! Unless you want to rebuild it before installing it. As for the gear ratio: I run 3.73 gears in my truck and my Son's and that gear ratio works great for all around driving. I personally would not go higer than a 3.42 gear, because you will loose what you are working for in the end with anything higher than that. Personal experience---My son's truck had a 3.08 geared rear end in ti , when we put in the OD tranny and we lost gas mileage, due to the truck working harder to make up speed and go over hills. My truck had a 3.42 geared rear end and it had to work more than I wanted it to to keep the cruise working on hills. The 3.73 gears allows my 383 stroker top work easily on the highway and to burn tires on the street. When we changed the son's truck to 3.73 gears the change in gas mileage wasa PLUS, going from 11 MPG to 14.5 MPG.


Our trannys do NOT have the lockup converters on them. We chose to eliminate that part and we still get the OD, just not that final lockup thing. I even have a 2400 stall converter on mine, due to the cam that I have in my engine. However I would do the change out again and even connect the lockup electrical switch. It was a great improvement to my truck. My DD is a 91 Silverado SWB with a 5.7 litre and 700 R4, and 3.42 gears. It gets about 20 MPG on the highway (it is a TBI truck) and it runs great. The fuel injection makes a remarkable difference in the driving on the highway.

[BigSky71]

Originally Posted by piecesparts

On myt ruck and my son's truck, the exchange was not that hard. ...

Our trannys do NOT have the lockup converters on them. We chose to eliminate that part and we still get the OD, just not that final lockup thing.

In the research I have done I have seen this option advertised, a change to non-lockup that as I understand eliminates the whole TV cable setup, which obviously would make the installation easier. PParts, do you run the TV cable on your non-lockup 700s? In the Transgo ad I read that the non-lockup has a "negligable" effect on fuel mileage, so non-lockup sounds like a win/win to me unless it caused an overheat issue...

[zerwar]

Originally Posted by BigSky71

In the research I have done I have seen this option advertised, a change to non-lockup that as I understand eliminates the whole TV cable setup, which obviously would make the installation easier. ..

You have to run the TV cable because thats what controls your shifts.......no tv cable = Toasted 700R tranny

Yes it is really needed. This is the most misunderstood part of installing a
TH-700R4 and getting it correct is critical to the very survival of these transmissions. This TV cable system controls the internal hydraulic pumps production of hydraulic pressure and volume, if that isn't enough, it also has a major influence on shift timing, quality and "feel".


check out this link http://www.btobeta.com/700R4/

[piecesparts]

Originally Posted by BigSky71

In the research I have done I have seen this option advertised, a change to non-lockup that as I understand eliminates the whole TV cable setup, which obviously would make the installation easier. PParts, do you run the TV cable on your non-lockup 700s? In the Transgo ad I read that the non-lockup has a "negligable" effect on fuel mileage, so non-lockup sounds like a win/win to me unless it caused an overheat issue...

In the late Nineties, I originally purchased the trannies for my truck (84 GMC) and my son's truck (86 Silverado) from a company called "Premier Performance", which is now the "JET Performance" company ( http://www.jetchip.com/ ). They sold their TH-700 trannies with the lockup feature removed BUT that was all--they still have the TV cable for the valve body to work. The trannies were sold with stall converters for a better use of the engine's power. I moved on from their intial 2200 stall to a 2400 stall and it works quite well. I have taken those trannies and rebuilt them to a heavier duty tranny and updated the planetaries in them to match what is on the market today. I have used the "Transgo" kits, and they are a good quality product. I get decent mileage for a 400+ HP motor and 3.73 gears and it does run well. Since the original purchase the trannies have gone through quite a change in my trucks and are stronger than before. The valve bodies still have the Transgo kits in them.

My Daily Driver is still a full fledged 700R4 tranny with the lockup converter and all of the original design parts. However, it has been also built up with the heavier duty clutch packs, larger planetary, Corvette governor, and sun gears, as well as a stronger valve body. It will kick your butt when shifting.

[streetstar]

$175, is a decent price for a rebuildable core i think -- but i wouldnt expect it to be reliable unless you had it gone through first.

'84 model shouldn't be a big deal as long as the trans shop rebuilding it understands you are putting it into something intended to go sorta fast, and not an old Fleetwood in a Donker project or something