T-400 to 700r4 in '84 C20 sub,454,4.11s

[Darth Vader]

I think it was like the last one on earth.....company in Texas called Unique Concepts (I think).
I called them and they said they didn't have any more and while I was talking to him I noticed a link for e-bay on their website.......clicked it and made an offer. $200 w/ shipping.
I checked it out w/ my local auto parts supplier....he said he could get one for $175 + S&H.

Heres a link to where I bought mine:
http://www.ebay.com/usr/uniqueconceptsusa?_trksid=p2047675.l2559

Go Industries:

http://www.goindustries.com/home/go1/page_81/down-spoiler-chevygmc-pickup-81-87-and-suburbanbla

 

[89Suburban]

That thing is sweet. Where are you in PA?

 

[Darth Vader]

Butler, Pa....'bout an hour North of Pittsburgh, Pa

 

[89Suburban]

Butler, Pa....'bout an hour North of Pittsburgh, Pa

I lived a few years in Clearfield area. And I got a buddy over in Waynsesburg. Never made up to your part of the state. I'd like to take the boat up to Erie, it's on my bucket list.

 

[MadOgre]

For about $700 you can have everything needed to run a 4L80E minus the transmission. But 2wd 4L80s should be pretty reasonable to pick up at the wreckers and they should give you 90 days return on it too.

You could probably have a running 4l80 for $1000 or less.

Use the FAST transmission control module =$5-600, And use there TPS sensor as well, it hooks to the carb like your TV cable would and then the other end is a self contained TPS sensor that you can mount just about any where. Plug your transmission controller into that and your transmission and your done.

Just be sure to grab the cross member from the junk yard donor

Once you have your cross member figured out you would have to shorten the drive shaft 1 1/2 inches

 

[80goldenburb]

It has a 454 and 4.11 gears. I'll use it for towing my '66 GTO. Car and trailer weigh 6500# combined.

if your 7.4 is factory specs, your 700 will hold up. Torque is killer of auto OD transmissions. most 700s are rated for 400 lb ft. the stock big block that year is 360-370, so yould be fine. 7k max trailer weight rating. I go that from my previous suburban ('85 1/2 ton 305/700r4/3.73 geared HD tow package). Main thing is to install a temp gauge and watch out if the trans oil gets hot. Don't allow it to hunt between gears as that creates heat. OD on flat roads is fine, drop to 3rd gear on ANY incline.

Anyone done this conversion and can tell me what I'll need to swap? Any specific cross member I'll need or a driveshaft that I caqn use that won't need to be shortened?

The trans crossmember will need to be bolted 4 3/4 inches FORWARD from its factory position for correct trans mounting. The driveshaft does not need to be modified as the th400 is the shortest version (with a 4 inch tailshaft). The 700 is only 2 inches in difference so it technically a direct swap. Youll need a 27 spline c clip yoke that will be used with the 700 output shaft and will attach to the driveshaft. Thats it.

Carb brackets from a newer year that will bolt onto the quadra-jet and aleviate and TV cable alignment woes?

Quadrajets on 305/350 motors from 82 and up had a TV cable bracket and a welded stud on throttle lever. You can swap the primary lever onto your current one or just get a whole new carb. They go for cheap. I copped one for $30 on craigslist.

I have what I believe to be an '89 700r4core and I also have access to a reasonably fresh '84 700R4 for $200.

Any '86 and newer core is what you want. they had the tougher guts and upgrades.

Gear Vendors are awesome, but they're so expensive, unless you're driving 100 miles day, they'd take forever to pay off.

Inferior 0.78 OD ratio that almost makes no difference with 4.11s and a slipping non lock up converter,the th400 will be running hot like it does at 1:1 ratio. taller 3.21s will make a better differences in rpms but still not as good as the 700r4.

 

[HotRodPC]

I'd pass on the 84 700r4 for $200 and build the 89. It's 87 and up that are the better units, and preferably the 88 and up. 86 down are the bad units, 82-84 being the worst units.

 

[Derick C.]

The 700r in my 90 burb works great. I tow regularly and the temp rarely gets up to 180 usually runs about 160 unless I am pulling a long hill.

I am getting ready to put a stock 454 in front of it. We will see how it does.

You must be registered for see images attach

This is what I tow most of the time. It is small but it is old and very heavy for its size. 4600 without all the toys in it.

 

[HotRodPC]

The 88 and up units have more corrections, seconday valve body, more splines and better hardened parts in them. Still doesn't make them bullet proof, but certainly stronger than the early units. With some mods to the 88 and up units like Vette Servo, Trans Go Jr shift kit, Beast or Smart Sunshell and Raysbestos Z pak or Alto Commercial 3/4 clutch pack they can be OK units. In the one I build, I intend to use a wider 2/4 band also and a Super Hold 3/4 servo and try towing in OD and see how that works. Hold the clutches tight enough, converter locked up that should keep the heat down.

Also if you intend to see over 5000 rpm frequently, you should sleeve the input drum otherwise you'll have issues stripping or breaking the input drum where shaft comes in.

 

[80goldenburb]

i just want to point out to everyone that any 700 manufactured after 0ctober 1986 is the same as the commonly advertised "88-93 better units" ive seen all to often. Also 27 spline input shaft was upgraded to 30 in mid '84.

 

[bucket]

Unfortunately, the 700r4 will likely die an untimely death even if properly built. I mean, you might get several years and 50K out of it, but the current th400 will probably last that long as it is. Having overdrive will save on engine wear and tear, but if you are primarily towing, you won't really gain much mileage.

Just quoting myself because I still strongly feel this way, lol. I've killed 700R4's with stock and mild small blocks. Not from abuse or neglect, just from using the car or truck how it was supposed to be used.

 

[80goldenburb]

Just quoting myself because I still strongly feel this way, lol. I've killed 700R4's with stock and mild small blocks. Not from abuse or neglect, just from using the car or truck how it was supposed to be used.

Nothing lives forever, but with mild 350 breaking a 700 means it wasnt properly built with tougher guts. Inability to break traction at WOT is a big killer also. especially anything above 400 lb ft torque.

 

[74 Shortbed]

I have a stock 700R in mine, even hauled a few vehicles on my trailer with it just fine, I just don't tow in overdrive. I will be building it up when I put the big block in though..

 

[bucket]

Nothing lives forever, but with mild 350 breaking a 700 means it wasnt properly built with tougher guts. Inability to break traction at WOT is a big killer also. especially anything above 400 lb ft torque.

Some have been properly built by a trustworthy shop that knows what they are doing. Others were stock GM units in a stock application.

In a truck application that sees much towing, a stock th400 will outlast any built 700r4. There's also no MPG benefit if you can't use overdrive. A 700r4 simply doesn't belong in a 3/4 or 1 ton truck. Been there, done that... it doesn't work. Yeah, I've got almost 70K so far out of the last one, but it has about every part you can throw at it and I've babied it the entire time. And that's behind a stock TBI 350. I have a big block that's going into the truck, and a th400 to go behind it. It's what I should have done from the start.

 

[80goldenburb]

In a truck application that sees much towing, a stock th400 will outlast any built 700r4.

Im not disagreeing with that. With a 700, it depends on how much weight your towing and making sure no overheating occurs (by hooking up aftermarket gauge). Most of em dont last because they are not taken care of. 400s can suffer the same demise. the one in my suburban ran hot and slipped all 3 gears on a 660 mi round trip. I had to park and wait for it to cool down multiple times. Smelled of burnt fluid since the day I bought it too. Also has a faint whine and harsh 1-2 shift. th400 is FAR from bulletproof when its not maintained.

There's also no MPG benefit if you can't use overdrive.

Ive towed 4k with a 97 suburban (350 Vortec/stock 91 700r4/3.42 gear/stock tire size) in OD on FLAT land at 70-75 mph and got 15 MPG.

My current Burb gets a whopping 10 mpg at 2k rpm (54 mph) with 454/400/3.21's. With my 700 swap soon to be, Ill be revving 1670 at 70 mph. There's DEFINITELY a benefit if your not towing too heavy of a load or do alot of highway cruising.

I have a big block that's going into the truck, and a th400 to go behind it. It's what I should have done from the start.

a manual valve bodied 4l80 would be more ideal. Durability plus an OD gear, especially if you have steep rear gears.