tatersalad

Gents,

Is there any real downside to using a non-locking conveter in a 200-4r. It's going in a stock engine 80. The wiring kits don't look to difficult to install, so locking is probably the way to go, but if there is no real downside...................

Schmucker

About 3% increase in fuel economy by having a lockup converter.

gkull

Please explain to me why you would want Over Drive in a stock 80?

How many RPM are you doing going down the highway right now.

tatersalad

Basically, I don't like the way it drives now.

It's turning about 2800-2900rpm at 70mph. OD will drop that to approx 2000. I think it will cruise much better, and obviously the mpg will go up as well.

My car is the LG4 engine which eventually I'll replace. Being it's an LG4 car, I didn't figure I had anything to lose changing the original engine and transmission.

page62

Locking. Period. End of discussion.

joe73vette

The big reason to use a locking converter in overdrive trannys is because you are cruising on the highway with the motor below the converter's stall speed. This puts a tremendous amount of heat into the fluid. Locking the converter prevents all that slippage and heat. Joe

isosceles

according to Bowtie, heat is the #1 cause of tranny failure. Also, the slipping conveter is the #1 cause of heat in the tranny. If wired correctly, it will unlock when it should (like when you step on the brakes or flick a switch) and remain ulocked until it reaches the stated RPM.

tatersalad

Thanks Joe. That makes sense to me. Locking it is.

UKPaul

My '81 did 3000 rpm at 70mph (no locking converter with Th350C). A 200-4r gives rpms of 2000 @ 75mph with converter locked (rear of 2.87:1). Without locking the converter & a trans fluid temp gauge fitted you can watch the temps climbing right up. For the effort involved wire it up to lock for fuel economy, life of the trans & better engine braking (with the converter locked it fills a bit more like a manual than a soggy auto).

gkull

The reason I ask your present rpm is: I had trouble driving my 3.55 rearend gear ratio in OD. If you have 2.87 to begin with here is what will happen. Do you really think you have the power without lugging the motor to drive around in lockup 4th gear?

Transmission Ratios: with stock TH350
1st: 2.52 2nd: 1.52 3rd: 1

Tire Diameter 1: 27 inches
Rear Gear Ratio 1: 2.87:1
MPH
RPM 1st 2nd 3rd 4th 5th 6th
1000 11 18 27 0 0 0
1500 16 27 41 0 0 0
2000 22 36 55 0 0 0
2500 27 45 69 0 0 0
3000 33 54 82 0 0 0
3500 38 63 96 0 0 0
4000 44 72 110 0 0 0
4500 49 81 123 0 0 0
5000 54 90 137 0 0 0
5500 60 99 151 0 0 0
6000 65 108 165 0 0 0

Transmission Ratios: with 200R4
1st: 2.74 2nd: 1.57 3rd: 1 4th: 0.67

Tire Diameter 1: 27 inches
Rear Gear Ratio 1: 2.87:1
MPH
RPM 1st 2nd 3rd 4th 5th 6th
1000 10 17 27 41 0 0
1500 15 26 41 61 0 0
2000 20 35 55 82 0 0
2500 25 44 69 102 0 0
3000 30 52 82 123 0 0
3500 35 61 96 143 0 0
4000 40 70 110 164 0 0
4500 45 79 123 184 0 0
5000 50 87 137 205 0 0
5500 55 96 151 225 0 0
6000 60 105 165 246

tatersalad

Not having enough power is actually a concern my brother has as well about doing this.

I'm either driving in town or doing 70+ mph on the freeway. So I'm hoping it's not a problem, but......

What kind of power do you think it will take? Sounds like a good excuse to build an engine .

I'm getting the transmission for free BTW.

page62

...and where did this transmission come from? The reason I'm asking is that a stock 200-4R probably won't live very long in your car...

ICEMAN59

According to Bowtie and my GM certified mechanic without the lock the converter will be slipping (searching) constantly. The whole idea of a OD tranny is to get max performance and fuel economy. If the converter is slipping you are defeating both purposes and are putting unneccesssary wear on the trany and converter . Locking is the only way to go for anyone with comon sense

tatersalad

A transmission shop owes my brother (an attorney) a lot of money, and this is a way of paying up a little bit. It will be beefed up a bit, and I don't plan on racing, so it should be OK.

I think there is no question about the converter. It has to be locking. My bigger concern at this point is driveability. Is this too high gearing for a 180hp motor? It's probably right on the edge. I know this is a common transmission to put in a C3, and they can't all be for racing.

I plan on building a motor at some point anyway.

AD2VET

I don't see your point. My '82, with the 700r, has similar ratios and I haven’t had any engine problems although I have gotten into the habit of dropping it into 3rd around town unless I’m consistently going over 40/45 mph.

As far as 180hp not being enough, my ’82 was only rated at 200.

UKPaul

I know I do! I have to manually shift into 3 when the speed drops to below 55/60mph (no problem as I've driven cars with manual g/box's all my life), but once above 60mph the motor will pull quite strongly in 4th with the converter locked. I guess if I was doing 50-55mph it might be a different story, but at highway speeds (60mph upwards) the OD is brilliant. No longer do I have to pace Nissan Micras, Fiat Puntos, etc at highway speeds with my exhausts howling away at over 3000rpm, it now burbles along at just over 2000rpm Glasspacks on the end of duals make one heck of a din at around 3500rpm &, to be honest, cruising at those speeds at high revs (for a SBC) & making all that noise while alongside an econobox is a good way of feeling like a complete pratt! Far better to rumble along at just above 2000rpm. Having happily kept up with ZR1's, C5's & a blown C4 while cruising between 2000 & 3000 rpms I'm happy to say that my puny L81 has adequate power to run an OD trans (the torque figures aren't that bad for it & the curve shows most of the torque available at the engine speeds we'll be doing most cruising). 2 other C3's with us were literally miles behind as they slowed down after finding that they were cruising at very high rpms (one was running at the red line with 3.55 rear gears). In case any of our boys in blue are reading this, the above was done in another country
For sprightly accelertion & general playing I just knock it into "3" and leave it there as I wouldn't expect an OD gear to give a lot of pull (I'd be pissed off it it did - it wouldn't really be an OD gear if there was bags of power in it). At the other end of the scale, the 1st gear is a lower ratio than the Th350 had, giving better get up & go from standing (& lets face it, a pretty much stock L81 needs all the help it can get!).

No way am I going to question your engine (the only question I've got is can you send it over when you've finished with it ) but I'm surprised that it didn't like OD with a 3.55 rear end Have you got most of the torque at the upper end of the rev range?

vetteman1100

Interesting! My 81' has a locking TC. Since you are in England, did the export version not have locking TCs?

GasketDude

I installed a 200R4 in my '71 Cutlass Conv. a few years back. Got it from a bone yard for $250. Did some research on how to beef it up and ended up going with Art Carr products. Look here for info about Lock vs. Non-Lockup. I ran the Non-Lockup, the way the fluid flows is the issue when in OD, so an additional trans cooler is required (plumb seperate from Radiator). The torque converter was cheaper in Non-Lockup if I remember correctly (2200 stall).

You could probably get away with a few minor upgrades if you find a 200R4 from a Monte Carlo ('84-'86) and don't get carried away with engine power later on. Setup in your Vette will be easier because O.D.'s were more common in Chevy's than Olds.

Your carb's throttle arm may need to be modified for the T.V. cable to operate correctly (T.V. cable pin 1 1/8" away from throttle shaft c/c). On my Olds this was the biggest hurtle, as none of the GM brakets worked with my old style carb. Did some custom fab'in to make it work.

Highway driving was much better with the 3.73 gear I was running. Never did follow up with the MPG gains as I sold the car to buddy who is doing a frame off resto on it currently.

gkull

UKPaul - It's going for very cheap today. Some reassembly required. It's actually what's left of my original L-82. It's a pretty bare short block that's been sitting on my garage floor with one of the melted pistons removed. It failed the test and My car got a 400 some mile ride home on a car trailor.

It was a low 400 hp class 355 ci with 10.7 compression, nice heads, 7000+ rpm. Just a refresh with a couple of new pistons and your heads and it's all ready to bolt back together!
**************************************** *************

I was actually very dissapointed when I installed my 700R4. It actually slowed down .2 or .3 seconds in the 1/4


I have a friend with a nice 383 ci and 3.08 rear gears and he keeps kicking around the idea of 3.73 rear gears.

Somebody ask what's the point? Well just look at the MPH chart in 4th gear lockup. That car has to be a dog. I doubt if it will ever even go much over 3000 rpm. It will be a car that can go faster in third gear than 4th. Lugging a motor is worse for ware and mileage than a properly geared car.

Yes UKPaul it didn't run very well below 2000 rpm with it's cam and single plane

UKPaul

Yes it had lockup. It used to run 2700rpm @ 70mph & then one day it started running 3000rpm @ 70mph. The archives around 3 years back will have large amounts of posts from me re: TCC lockup. I never fixed it. I was driving down roads at night & getting my wife to connect wires to ground, others to +12v, etc & concluded that the converter or trans had failed. After I fitted the 200-4r the computer still didn't ask for lockup (so I had a fault with both the ECU & the trans/converter). I think the ECU problem might be because I'd fitted a 180 stat (maybe the ECU didn't think the coolant was warm enough to allow lockup?). I can't be bothered to change the wiring to find out as it works how I want it at the moment. I also took the TCC solenoid out of the Th350C one evening & found one of the tiny oilways gummed up with that horrible swarf you find in the pan, which may explain why the TCC didn't lock when my wife was feeding 12v to it & earthing the return? It's a lot easier finding things like that on the bench than it is lying under a car with a torch
Gkull,
It's not unusual to be able to go faster in a lower gear than in OD. 3000rpms equates to 123mph in OD & mine was pulling OK at that speed (in another country ) & didn't feel like it was lugging. As I said, for generally going mad you'd be better off putting it in 3 & keeping it there. This also applies to modern autos who's owners I've spoken to about it. I've only been in a couple of other types of car with OD autos but both had computer controls that prevented OD from engaging at low rpms (to prevent lugging) & I assume that at higher rpms they'd either run out of steam or get shifted down a gear? The problem with finding out is that our national speed limit is 70mph. Any speed over 100mph gets you an instant driving ban & I think they shoot you for anything over double the posted limit As I understand it, OD is really that, an overgeared ratio that is fine for cruising in the region of the powerband where peak torque is found. It's not an extra gear that you'd expect the engine to pull all the way up to the red line in. The problem with throwing OD units behind C3 motors is that there isn't a computer to prevent OD engagement at low rpms, so the driver has to shift between 3 & OD manually.
Damaging the engine? When cruising behind later Vettes at around 3000rpm mine didn't feel like it was lugging at all. It would pull OK to match any gentle acceleration, but if a couple of ZR1's, C5's & a supercharged LT4 decide to hammer off down the road then a very mildly tuned L81 is gonna have to drop a gear or 2 to stay with them. I had no concerns about my engine at the time, in fact I was really happy at how well it ran - it was singing right in the middle of it's powerband The guy behind with a th350 who was constantly running at 5000rpm was very worried about his engine!!
Look at it this way, if a C3 had the power to pull up to 5000rpm with an OD installed then we'd all be peering into the jaws of death! 205mph in a C3? No thanks, f that!!!! Mine felt fine at the speeds we were doing, but we were on high speed roads with good surfaces. If they'd been twisty roads with bad surfaces I don't think I'd have stayed with the later Vettes. And always at the back of my mind is the fact that one of my wife's Canadian cousins was killed when his C3 left the road at over 140mph. So my 200-4r lets the engine pull to speeds at well over what I would normally do on public highways & if I want to go faster & have more acceleration I'll just use 3 (which reminds me that I must wire up the locking TCC for 3 - something I was going to do last winter ). Consequently I'm very happy with it, it drops cruising speed rpms down & saves on fuel (liquid gold in England!). If you're using it on a track then it's a different matter, but why would you want an auto in a track car?? Put in a stick shift (manual) 5 or 6 speed & really enjoy yourself