74 NovaMan's 1979 Chevy Truck - LS Swap - 5/6 Drop

[DanStokes]

Fashions change...........

Dan

[Deaf Bob]

Green and purple carpet!

Stiny be PIMPIN in his PIMPMOBILE!

[silver_bullet]

Chris,
Have you considered BFG Radial TA 295/50R15? It would fit the stock 15X8 wheel. I used to run 31X10,50X15 on my old C-10's

[Russell]

Green and purple carpet!

[74NovaMan]

That's great! Thanks!

[STINEY]

Underhood vacuum switch that takes the signal from the carb and completes the electrical signal to the transmission. Only allows lockup with high vacuum signal, and unlocks as soon as the signal drops (throttle blades open further)

Literally a ignition hot input and output.


Underdash showing the other end of the wires above.

I spliced a toggle switch into the circuit, and a indicator light so I could "see" the converter lock and unlock.



Black toggle is the one I used to control lockup. The red light below lights up when locked. Not necessary but interesting to watch at first......later was lots of fun as passengers would panic when the red light came on! Oh my!



Not much to it in reality. Very simple to figure out if already there, and very easy to add to a vehicle without th350c lockup from the factory.

Hope this helps.

[74NovaMan]

need to figure your tire diameter in to the overall gear ratio as well... I'd probably run a 3.42 with the OD 3.31 without...just my personal experience...3.73 works well with a 31 inch tire... about 2000 rpm at 70 mph...in OD...locked converter...

As much as I like the stock rims that are on it, options for the 15" rim in a low profile wide tire are not good. Tires that are on it have like new tread but are 7 years old. The stock replacement tires are about 28.3 inches tall. When the time comes I am hoping to get a set of these:





and wrap them with these:



It's a 245/50 R16 - the same tire the Camaro takes. (cheap and available and not likely to go out of production soon - I hope) 25.7 inches tall with a 8.5 inch tread width and 10 inch section width. I'll probably want to lower it some first.

[74NovaMan]

Then I decided to hook up the little vacuum switch that engages the lockup electrically just to play with it. Wired in a toggle switch to be able to deactivate lockup from the drivers seat. That did come in handy while towing on long gradual grades, it tended to "hunt" a little bit.

Reading back over your post reminds me that my first 700r4 (in the Nova) used a vacuum switch for lockup and I remember liking that setup better. You have me rethinking my no lockup decision. I ran some math and figure if I drive 10,000 miles a year (which would be using it as my summer DD) and I can increase mileage by 3 mpg (with overdrive and/or lockup) it is as much as $500/year, figuring a 14 mpg starting point. If I only drive 2,000 miles per year (more likely), that same 3 mpg gain only nets me $100.

If you need pictures or info on how the 350c lockup is actuated let me know, I'll snap pictures and spill the beans.

That would be very helpful. I'm guessing that that would be applicable for the 700r4 as well. Thanks for the help.

Edit: The savings above were calculated at $4 per gallon.

[STINEY]

Do you have any feel for how much you gained (mpg-wise) with the lockup?

It gained a solid 3 mpg. 1980 Chevy Vandura 1/2 ton, all the aero of a breadbox, edelbrock intake and carb, mild rv cam, dual 2 1/4" exhaust thru turbo mufflers, #4000 on the scales, driven like a punk kid - 15 mpg. Parked it when gas prices shot up around 2004?

I wonder if the TH350C and the 700R4 use the same converter? Sounds like something GM would do.....

If you need pictures or info on how the 350c lockup is actuated let me know, I'll snap pictures and spill the beans.

[silver_bullet]

need to figure your tire diameter in to the overall gear ratio as well... I'd probably run a 3.42 with the OD 3.31 without...just my personal experience...3.73 works well with a 31 inch tire... about 2000 rpm at 70 mph...in OD...locked converter...

[74NovaMan]

What's the rear end ratio?

That is a good question. I would guess its a 2.7 or something in that range based on the freeway behavior on the trip home. I'd like to upgrade to a 3.08 or 3.23 posi at some point which is another argument for overdrive.

[74NovaMan]

My last van had a TH350C.....local guy rebuilt it for me. Said it took all the same standard rebuild parts (he added extra plates/discs since it was originally behind a 250 I6) except for the converter.

I drove it for a couple years with it unhooked. No problems. Then I decided to hook up the little vacuum switch that engages the lockup electrically just to play with it. Wired in a toggle switch to be able to deactivate lockup from the drivers seat. That did come in handy while towing on long gradual grades, it tended to "hunt" a little bit.

I put over 120,000 miles on it, and its still good. Planning on putting it in a different project now.

Overall the lockup function saved me a bunch of fuel money. I'd keep it unless the converter is unavailable or way overpriced?

Thanks for chiming in. I haven't been a fan of the lockup converter in my Nova (700R4) and mileage seemed to improve on that one when I disconnected it. It started acting funny about half way through power tour in 2013. We averaged 17 mpg over 1,007 miles to get to the start and almost 18 mpg for 1,270 miles on the way home. I'm sure that result is a atypical but I also like how it behaves without the lockup.

If I do the 700R4 in the truck, I was planning on using a non lockup converter figuring I'd gain enough mpg-wise with the overdrive.

Do you have any feel for how much you gained (mpg-wise) with the lockup?

[STINEY]

My last van had a TH350C.....local guy rebuilt it for me. Said it took all the same standard rebuild parts (he added extra plates/discs since it was originally behind a 250 I6) except for the converter.

I drove it for a couple years with it unhooked. No problems. Then I decided to hook up the little vacuum switch that engages the lockup electrically just to play with it. Wired in a toggle switch to be able to deactivate lockup from the drivers seat. That did come in handy while towing on long gradual grades, it tended to "hunt" a little bit.

I put over 120,000 miles on it, and its still good. Planning on putting it in a different project now.

Overall the lockup function saved me a bunch of fuel money. I'd keep it unless the converter is unavailable or way overpriced?

[Stewzer55]

What's the rear end ratio?

[74NovaMan]

I found a cork trans pan gasket and installed it. Same huge puddles as before. One leak is through the center of the slip yoke (the rear seal is completely dry but fluid is dripping off the u-joint.) The speedo cable is also dripping. I pulled the pan back off and got an aluminum pan thinking that was still the majority of my issue but the drain plug hole was not threaded well so I had to wait for a new one to exchange it for.

While this is going on I figured out that the transmission is actually a TH350C (the lockup version - wiring not connected - nor is the kickdown cable). That information coupled with the leaks and poor shifting characteristics has me thinking about finding a TH350 to rebuild for it or rebuilding and installing the 700R4 I have sitting on the shop floor. The TH350C in it now is the long tailshaft version so apparently my driveshaft will work so I'm looking at probably $1,000 - $1,200 for the 700R4 (rebuild, converter and TV cable setup). A TH350 will run me about $800 - $900 assuming I can find a good core. If I return the aluminum trans pan ($84) the gap closes even more. I could easily go either way but I was really hoping to spend that money on more fun stuff (not that I have these funds in hand waiting to be spent.)