scottyp99

Hi, all,
I am thinking about swapping a 700r4 into my 1980 Corvette. It has the L48 engine with a th350 auto, and 3.07 rearend gears. I would like it if someonbe could give me a comprhensive list of issues I will be facing with this swap. For instance, I am aware that I will need to modify or replace the transmission crossmember, and have the drive shaft shortened by 3", but what other issues will come up? Can I use the shift linkage that is used on the th350, or do I have to get a new one? Can I use the mount that the kickdown cable is attached to with the tv cable, or do I have to get a new one? Can I use the torque converter from the th350 on the 700r4? The donor transmission I have is out of an '88 IROC Camaro, and I anticipate having approx. 350 horsepower at the crank, what sort of mods do I need to do to the trans internally (I am planning on at least a stock rebuid, as the donor car had 114,000 miles on the odometer) Also, what sort of issues have I not even mentioned, and are lurking to ambush me in the night. Thanks, folks,


Scott

mrvette

For internal rebuilding you need talk to TimAT, he is the tranny guy....knows as much or more than anyone....

replace the lockup solenoid...they get old, and hang up in one position or other.....

I would go with a TRANS GO shift kit.....but Tim can explain it all....

I also am more of a fan of the 200 4r as lighter, simpler, and just as reliable, apparently....

SIXFOOTER

+1 for the 2004R over the 700. Couple reasons: no drive shaft mod needed and depending on the year of the 700 it might need more mods to take the HP you want. That said:
as you mentioned xmember needs rework or replaced.
Shifter can be used but needs a $90 mod kit for the correct detents and silkscreen, kit from shiftworx.
Different torq converter
+1 on the transgo shift kit too.

scottyp99

OK, so the torque converter is definately different, and I will need to buy a new one. Do I REALLY need to buy a $90.00 mod kit, or is it just nice to have? I'm just gonna leave it in Drive, anyway, so what's the difference? How about stuff like tranny cooler lines? Can I use the existing ones, or do I need to get some for an '82 'vette, or what? Also, save yer breath when it comes to selling me on a 2004r, I've thought about it and made my decision, I have a 700r4, and that is what is going in the car. I like the low first gear ratio, to go with the relatively high axle ratio, and the wide 1st to 2nd spread doesn't bother me, my engine will be built to enjoy a wide, flat powercurve. What I'm looking for is a list of all the issues that will need to be dealt with, so I'm not sitting there with my car up on the lift, going "Huh, how come nobody ever told me I would need a new thing-a-ma-jig? Now I need to wait two weeks for one to come mail order! RATS!" OK, I'll check back tommorrow, and see if that Tim guy has spotted this thread, meanwhile, I'll search around on the internet and see if someone has maybe written an article about it or something. Thanks,


Scott

TimAT

I've never installed a 700 in a Vette, so Not much help there. I can tell you to get one from late 88 up to 92. The rear planetary set was one of the weak spots and they(GM) fixed that in late 88 model year.

Use a Trans-Go kit, get the Corvette Servo, TV valve, and reverse boost valves. Make sure it has at least a 10 vane pump with hard rings, and the drainback in the pump has been drilled out at leas to 1/4".

The stock shift plate/detent will work, you just won't be able to select manual low gear- I have a 200-4R in my 77- thats how I found out about the low gear thing.

You might have to tweak your cooler lines a bit to get them to fit but they are real close to the 350/400 locations. Close enough anyway.

Make sure your TV cable is adjusted properly and has the correct travel. Too loose, and line pressure won't build enough to keep the trans from slipping- too tight and it'll bang shifts- line pressure will be too high all the time.

markdtn

There are many posts on this topic, so do a search.

You need a different crossmember, shorten the driveshaft (I would never say an exact number, you really should measure),you can use your shifter if you modify the detent plate, you need a floor-shift 700R4 cable bracket-Fbody is fine, you can use the TH350 yoke. You can buy a conversion kit from BowTie Overdrives that has the detent, shift plate, and other parts. They also sell a nice tubular crossmember. You must use a 700R4 torque converter and you must adjust the TV cable before you start the car-it is that important. Various people sell carb brackets; for a Qjet you can use '83-86 truck or similar Impala/Caprice (w/ 700R4), for Holley or Edelbrock you can mod one of those or get an aftermarket one. The Tuned-Port Camaro TV cable is not correct for a carb application so you will need a different one from a carb car. Hope this helps.

scottyp99

OK, thanks for the info, I really appreciate it, I feel like I know what a little more about what I'm getting involved with now. I have a friend who has an '82, and retro fitted it with a manual transmission, he says he will sell me the old drive shaft for $50,I assume this will fit my car since '82s came with 700r4 tranny in them, and is cheaper than getting old one cut, any thoughts? He says he may also have the shifter and cable and detent plate , it should work on my car, shouldn't it? He doesn't have the old tranny lines, and he modified the crossmember for the manual, so it looks like I will be getting a new crossmember from bowties.
OK, so I am also gonna need a new tv cable?And a bracket on the carb linkage in order for the geometry to be correct for the tv cable, right? Will the attachment point on the intake manifold for the kickdown cable be correct for the tv cable, or do I need a new one of those too? How do I deal with the lockup converter? Is it better to get a non lockup converter and just not have to deal with it? I have heard the lockup converters are a lot heavier and really only give you a couple hundred rpm, so is it really worth it? Also, is there a rebuild kit that has everything I will need, or do I have to buy additional parts along with the rebuild kit?

Ahhh, the more answers I get the more questions I have!!! Sheesh! I am determined to have an overdrive, tho. Thanks,


Scott

markdtn

An '82 driveshaft only works in an aluminum diff car (80-82). Yes, the '82 shifter should work fine. For lockup you have choices-Painless (among others) has a vacuum kit or you can just go with a toggle switch. I would keep the lockup. Yes you need a 700R4 carb bracket and carb TV cable.

TimAT

Not having the lockup on a 700 is a quick way to cook it. that is a mandatory thing on the OD transmission. Without the lockup the trasn won't cool properly in 4th and it'll burn the thing up.
Having a simple toggle switch works, but you (or anyone that drives the car) have to remember to turn it on, and then turn it off when you stop. A locked convertor will act just like a manual trans car at a stop if the convertor is locked. I've seen TCC solenoids fail in the lockup position. When you stop, the engine dies.

rpoL98

I installed a 700R4 in my 78 behind my 540 big block, replaced the factory TH350.

you can take advantage of the TH350 crossmember brackets and fabricate a mount adapter that mounts to the trans case instead of the trans output shaft extension housing. I think the trans case provides a more solid mount than the extension housing. and it keeps the trans lower so the trans output u-joint don't hit the tunnel. You want the trans output extension hsg to be as close (low) as possible to the trans crossmember to provide tunnel clearance.

mounting adapter bracket was fab'd from some 2" x2" angle iron and some steel "strap" e.g. 2"wide x 1/8" thk. put it in a vise, bend, and hammer. then weld and paint and it looks beautiful. or you can use your original TH350 bracket that mounts to the front of the cross member and mess with the bolt holes. I didn't want to modify mine, so therefore the angle-iron solution.

you'll have to cut the parking-brake-cable wheel-mount off and angle it just a little bit different to clear the trans (welding req'd). it just gotta be a "functional" weld, don't have to be pretty or anything. and while you're at it, might as well fill in all the gaps on the skip welds on the trans cross member.

you can get by with your stock shifter but won't be able to pick up 1st gear manually, probably won't be able to get 2nd gear manually, but if you're only going to leave it in Drive (actually OD), then not a problem. I went to the trouble to install a C4 shifter in my console but there wasn't any advantage to that at all (dumb idea that didn't pan out but not worth the trouble of de-installing). you can modify your original shifter with a jigsaw (sabre saw) for the detents and 1st, 2nd gear.

yup, you'll have to change the drive shaft. I got mine from Denny's (it's a Work of Art!) but I forgot the dimensions. I know it wasn't an even 3", there was some fractions involved for the "just right" length.

trans output yoke is the same. I used the GM torque converter that came with the trans (package deal), no problem yet. no torque converter interchange between TH350 and 700R4 at all, no way.

I wired in the lockup so that it locks up anytime it's in 4th gear. forget the vacuum unlock, and brake pedal switch unlock, those make for a cumbersome driving experience, trust me. I had bought the Painless Wiring whole darn kit, but ending up bypassing the vacuum switch and brake light switch, too annoying. The PW kit included the 4th gear pressure switch which is attached to the trans valve body, the wires come out from the factory connector on the trans. You could probably get just the pressure switch separately (it had a GM part number... long since forgotten).

you'll have to play with the governor to get the desired 4th gear shift point. a shift kit is mandatory, of course, and a cooler in addition to the built-in radiator cooler is always desirable. I mounted my trans cooler in series, using some fab'd aluminum angle brackets and large hose clamps to the big vacuum reservoir at the front of the nose, I think it's the vac reservoir for the headlight doors. been many years, and never has budged or gotten loose.

I had bought a later-year C4 governor but never got around to installing it (my trans originally came out of an camaro). I've learned to live with the "somewhat mundane" shift point. I did have to change the extension hsg to the "Caprice" version (avail from GM parts) since i didn't have any use for a torque arm hookup which also got in the way of the tunnel. It comes with a new bushing and seal. the latest version of the bushing looks like a golf ball surface, I guess for oil retention, "science".

1st gear on the 700R4 is just plain mean. you'll have to be very careful on rainy days, my rear end always breaks loose on curves with just the slightest gas pedal twitch! especially on the 1-2 shift. that's with the standard 255 rear tires.

I hooked up the TV cable to the readily available adapter stud that bolts to the lowest bolt hole on my Holley double pumper throttle shaft bracket. modified a Holley throttle cable bracket which has got the lower fitting for the TV cable to clear my 14" open element air cleaner. the lower bolt hole on the Holley throttle bracket is pretty darn close to all those "engineering recommendations" for TV cable arc movement specs. I measured it and it's been very satisfactory, no trans burn-out problems (after many years).

I put on a TCI deep pan, but it hits every darn speed bump, so I have to come to a complete stop for those before proceeding very slowly (I guess that's the intended purpose of the speed bump...). small price to pay.

the trans that I rebuilt was an '88. I think the word is that you don't want to use anything before that year because of all the bugs. the later, the better. I used a combination of (the original) Art Carr, TCI, and B&M parts in the rebuild, along with the hard parts that were available back then (e.g. sun shell, etc). Nowadays, there's some really good hard parts available.

I don't have a shift indicator working yet, but I'm kinda leaning towards a DakotaDigital setup, just haven't gotten around to it yet. If I hadn't changed to the C4 shifter, I could've gotten by with the stock TH350 indicator (just wouldn't indicate 1st gear, etc).

well, that's kind of a memory dump for what I did a few years back to make it all fit and work. haven't had any problems yet, pretty darn reliable, the least of my worries.

george2066

hey rpol98, ditch the low vac and brake sw, is that why mine sometimes goes in lockup, driving issues?

rpoL98

I did ditch the low vac and brake light switch, they've been bypassed for a long time already.

I bypassed those because, when you use the brakes just to decelerate slightly for highway cruising, the de-coupling of the trans clutch and re-engaging was very annoying. makes the cruising very un-smooth.

similarly for when the vac switch decided to disengage the TCC when approaching a slight hill. my BB 540 has enough torque that didn't need to dis-engage the lock-up. even with the small block in my car before the BB, didn't need to unlock the TCC just for a small hill if it's still in 4th gear.

leaving the TCC locked up anytime you're in 4th gear has worked very fine for me. by the time you come to a stop, the trans has already shifted out of 4th gear long time ago, so brake light switch is totally redundant.

and if the engine load (~vacuum) gets high enough (low vacuum), it's already downshifted (no longer in 4th), so that darn vac switch is also totally redundant.

but I guess the idea is to give you options.

redwingvette

I installed a B&M trans controller that works off the speedo cable. It locks up above 40mph and unlocks below 38, It has a switch that lets you setup the speeds that controls the lockup.
I found mine much cheaper then what is shown with this link.
B&M shift control unit

george2066

thanks rpoln8, 406 sb has plenty of power, that explanation makes a lot of sense.

scottyp99

Lots of good info here, keep it coming, folks. What else is lurking in the shadows for me to trip over?


Scott

scottyp99

Oh, one more thing. Is there a rebiuld kit that has everything I need in it? I don't wanna have to go around looking for parts, and worry that I missed something.


Scott

rpoL98

nope, there isn't a all-included hop-up kit. the rebuild kits have the clutches, maybe the steels, gaskets, seals, maybe bushings.

but for the serious hard parts, you'll have to shop for those, e.g. sun shell, planetaries, special clutch packs, (the list goes on and on...).

there's been a lot of magazine articles with details on these parts. some avail from GM since there's some interchangeability with the 4L65E.

71rdster

There may not be a complete kit that has everything you need, but there are a number of Transmission Performance parts vendors that provide one stop shopping. Search the web to find them. Look for vendors with an 800 number so you can call for advice from the "Pros" on selecting parts that meet your performance goals.

doctorgene

Yes Sir: Why don't you buy the cross member, The shifting tower, drive shaft, trans. cable bracket, (fits the cable to the trans pan) wiring loom off of an 1982. They will all fit right on to the older car. Lots of luck, Gene

markdtn

Not so. You cannot use an '82 driveshaft directly except in an '80-82 because when they went to the aluminum diff in '80 it moved the position of the front pinion and yoke. An '82 driveshaft will not fit an iron diff car-I know the hard way Also, the later crossmember has a different mounting and is only cut for single exhaust. The shift cable is the same for all C3 automatic cars from 78-82. You can modify the detent in the shifter to add overdrive or buy a new detent from BowTie for the existing shifter. It is not a difficult swap. If you use an '82 crossmember, you have to have an '82 tailhousing which are hard to come by. The BowTie crossmember uses the rear mounting holes just behind the pan so it doesn't care which tailhousing you use. Just be careful if you get a C4 transmission, the C4 700R4 is not tapped in those locations. I also found that out the hard way.