L81's TH350C Swapped for a TH200-4R

[GerryLP]

I had her transmission rebuilt a few years ago, and it runs very strong indeed; however, with fuel prices not ever returning to below $2.00 per gallon, I decided to find a way to extend her range and mileage.

The option was to either go back to her old rear end ratio (she now has 3.31:1 gears, and so she cruises 80 MPH at around 3,000 RPM), or swap the 350C for a 200-4r. And I felt that the new 4-speed auto would give her more range, and a better 1st gear for acceleration from dead stop. Also, the L81 engine should cruise at freeway speeds with just about 2,000 RPM's , which is a 33% improvement in lesser tear and wear of the engine, and lesser associated fuel usage.

Here is the 350C already out from the Vette. It is a very good tranny, but it has obviously been overshadowed by newer transmission designs, like the 200-4r.

GerryLP:cool

 

[Peer81]

You won't regret it! With my 700r4 I'm doing 2000rpm at 75mph (original diff ratio).
Are you also changing the gear indicator in the console?

Greetings Peter

 

[GerryLP]

Pull New Tranny from Crate

Well, here are Gail's new thighs.:L

It is a Level 2 Reptoid from PATC, in Louisiana.

Look at that larger intermediate servo (Well, it is most likely the size of servo that came with the Buick Grand National).

Here is the pump-side view...

And this is the left side profile...

The price included a new lock-up Tq converter as well. I could have gone as high as 2,800 stall, but I was driving her with the 350C and a 2,200 stall, and decided to save every bit of gas mileage. So I opted for an 1,800 stall.

They give you a choice of a T-Shirt or a cooler...really...,Really?, Really? :L

Not all is smooth, however. They forgot to send me the dip stick/tube and the TV cable as well. Luckily, I can install the tranny and fit those items in later.

GerryLP:cool

 

[GerryLP]

You won't regret it! With my 700r4 I'm doing 2000rpm at 75mph (original diff ratio).
Are you also changing the gear indicator in the console?

Greetings Peter

Hey Peter. Yes! I already ordered the kit from YearOne. I have a lot of work to do...:ugh:eyerole;squint:

GerryLP:cool

 

[22229stingray81]

Looking good Gerry! I can't wait for your full report on how it drives.


-Tatortot

 

[GerryLP]

Looking good Gerry! I can't wait for your full report on how it drives.


-Tatortot

Tatortot, my man!

Yeah, I can't wait either; however, I do have an idea how it will be cruising in the Interstate, for I have a bare-bones stock 200-4r in the Acadian, and in the highway, the matching-numbers 307 purrs along at 2,400 rpm with a 3.73:1 gears in the rear, and yielding 19 miles per gallon (and the engine does pack a Holley 4-barrel carburetor (stock was a 2-barrel), a Z-Series Aluminum Intake manifold (stock was a heavy cast iron manifold), an HEI distributor (stock was points-style distributor), and it even has a Dial-A-Mile kit on it withwhich one can control the fuel mixture(stock was a carburetor needle):L), but what I am anxious for is to put this tranny through the paces and hear Gail's engine roar past some rice-burner...:L

GerryLP:cool

 

[bill81vette]

Hope everything goes well for the tranny swap!!!!!!!

see you in Ill!!!!!!!

 

[Peer81]

Gerry,

I also have almost the same transaver radiator. I don't know if you're has normal mounting things but mine had tiewraps to hook up the transaver to the original radiator. I don't know if it works or not but I made a normal supporting frame from metal and mounted the frame to the evapurator frame.

Greetings Peter.

 

[GerryLP]

Hope everything goes well for the tranny swap!!!!!!!

see you in Ill!!!!!!!

Thanks Billy. It is getting a little snug in time, isn't it? But I hope to have it done by Wednesday. The new tranny is bolted in, so that leaves me about 4 hours of work left. A couple of hours Tuesday and two more Wednesday.

First thing tomorrow, I'll call PATC for them to ship me the missing dipstick and TV cable. Once I get those, it will be a matter of servicing the tranny, setting the TV cable, and perhaps even take her on a test drive. Then, I'll install the stick shift conversion kit.

GerryLP :cool

 

[GerryLP]

Ok. PATC is sending me the missing parts. The lady there appologized for the error. I explained to her my urgency, and said that I should have it by Friday, so while waiting, perhaps I'll start the shifter conversion kit installation.

GerryLP :cool

 

[bill81vette]

I hope she wasn't a.............................


Dipstick!!!!!!

 

[Peer81]

I hope your planning on installing the tv cable before putting the tranny under the car. Very difficult to do it the other way around.
Btw. Did they also change the lockup wiring for you? The 4 gear trannies use the same terminal wire to lockup second and third but a different for 4th. And our ECM doesn't have the other terminal to lockup a 4th gear.

Greetings Peter

 

[GerryLP]

I hope she wasn't a.............................


Dipstick!!!!!!

"Synthetic are synthetic!" ... That's a good one, Bill :L

No, she was very apologetic and told me that it was all her fault and that she felt bad...I told her,"Kim, as long as I get the parts by this Friday, then it should be ok."

GerryLP:cool

 

[GerryLP]

Well, the 29 teeth driven gear (green) is installed. I ordered the tranny with a 12 teeth drive gear, so that the speedometer will read correct.

Tonight, I installed the auxiliary tranny cooler. Peter, I was not able to get as fancy as you did with your installation. I just followed the instructions and installed it with the plastic ties that came with the kit. Keeping it clear from the hood, headlight vacuum motors, and other areas was a bit challenging, but right against the A-C condenser just behind the vacuum cannister worked best. And, that gap on the passenger side of the air dam was perfect to rout the hoses to make the connection.

I hope your planning on installing the tv cable before putting the tranny under the car. Very difficult to do it the other way around.
Btw. Did they also change the lockup wiring for you? The 4 gear trannies use the same terminal wire to lockup second and third but a different for 4th. And our ECM doesn't have the other terminal to lockup a 4th gear.

Greetings Peter

As far as the TV cable installation, I suspected as much in installing it, so I am not installing the cross-member just yet; however, the 200-4r is about the same dimensions of the 350C whereas the 700-R4 is more masive and closer in dimensions to a TH400.

They wanted me to send them a picture of the wiring on the 350C to make sure, but then I decided that I will make it work later during the tranny fluid change in a bout a year or so. They use a pressure switch for the lock-up in 4th gear. So, it will always lock-up. I am wondering If I am going to get a check engine light if the way they wired it is incompatible with the L81 computer...

GerryLP:cool

 

[Peer81]

No check light, my brake switch isn't working so the lockup is always on when I hook it up. and without the wire connected I don't get a check light.
As for the 4th gear lockup. Maybe if you check the wiring diagram on your and 200R4 you can make it work without tomuch problem. If the switch only needs 12v with a brake switch to disconnect the 12v then you can simply move the 12v wire from position A to position C (I think).

Greetings Peter

 

[GerryLP]

Progress so far on Wednesday night

Welll, I got a little closer to the goal tonight.

I connected the oil lines to the tranny, but I had to reshape them first. Expect to do the same if you swap your L81's tranny with a 200-4r.

I bolted the Tq converter to the flywheel. The instructions recommend to ensure that the converter is all the way seated (How to tell the converter is seated all the way into the tranny pump? well >>> one would compare the gap between flywheel and engine block with the gap between Tq converter bolt pads and flywheel. It is all the way seated when the gap on Tq converter side is deeper than the gap in engine block side). However, when bolting the Tq converter to flywheel, the gap has to be bridged with spacers, or one risks moving the Tq converter too far away from the tranny pump. So you'll see spacer washers in the image below...

The new cross member support is a bit tricky to align the first time around. Also, the E-Brake cable pulley bracket is there, but since the cross member sweeps aft about 6-1/2", the E-Brake cable loses some tension. One possible solution would be to drill another hole on the bracket closer to the cross member. Also, the cross member is a bit tricky, for it will bump against drive shaft if you allow shaft to just droop in place. A piece of wire would help raise the shaft and keep it out of the way until reconnecting the shaft with the yoke is needed. The stock hardware works better than the one included, and no long cross bolt is included.

The front "Y" pipe support braket now bumps against the catalytic converter, so I will have to manufacture another one in its place.

This is a longshot view of cross member support at the driver's side end.

The passenger side view.

The 350C converter cover does not align 100% without modification, so I'll purchase one for it on eBay or another place.

I have to yet install the dipstick/tube and TV cable. Hey Peter, I think it will be alright for the TV cable. I am a little more concerned with the dipstick giving me problems. :ugh;squint::L

GerryLP:cool

 

[GerryLP]

I received the dipstick/tube and TV cable today. They are installed. And just as I feared, the dipstick gave me a little problem, but I did not lose too much work. I had to undo the cross member and lower the tranny a couple of inches, but it was a lot easier now that the cross member was already in place.

Tomorrow I'll install the starter, front "Y" pipe, and the shifter kit. But it is ok, since I am starting my vacation tomorrow as well.

GerryLP:cool

 

[TimAT]

The plastic ties that they give you to hold the cooler to the radiator are a radiator shop's best friend. Thru heat and cool cycles (expand/contract) they will saw thru the tubes in the radiator. Then you get to pull the radiator and get it fixed.

 

[GerryLP]

The plastic ties that they give you to hold the cooler to the radiator are a radiator shop's best friend. Thru heat and cool cycles (expand/contract) they will saw thru the tubes in the radiator. Then you get to pull the radiator and get it fixed.

Perhaps...but with the limited time I have before Cruise Fest, I opted to use them. The ties are not your topicAL plastic tie. They have a roudish plastic flange of perhaps 3/4" diameter ( it is more of a hexagon with two sides longer than the other four sides). A plastic stem extend from it approximately 10 inches, and a separate capping flange completes the tie.

I was mostly concerned with it interfering with the electric fan on the other side, but the capping flange is low profile, and it is about 3/4" away from the fan's circular edge. So it will allow the fan to rotate.

GerryLP:cool

 

[GerryLP]

Well, today I accomplished a bit more. I installed the Shiftworks shifter kit. The kit is right-on. I had no problems installing it. The stock detent plate has to be taken out by drilling the spot welds on it, and the surprising thing was how the new plate fitted the holes just fine.

The shifter indicator was also relatively easy to put on. I just hate to remove bolts to the plastic holes in the console plate, for they tend to break easily. I was very patient, and luckily, I did not break anything.

The kits is also very complete. It even includes the cable bracket (the pan bracket), the shift shaft adapter, and all the hardware...even the cotter key's.

I have to fix the oil temp sensor wire, service the transsmission, and install the passenger side cold air duct, which I removed when I was messing with the oil cooler.

Cruise Fest is upon us! Let the fun begin!

GerryLP:cool