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

[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.)

[Scott Liggett]

I did not even notice that. Thanks for pointing it out. I'll add that to the list for when I get drop spindles.

Yes, they are worn. If you are going to the hassle of pulling off A-arms for bushings, do the ball joints as well. Maybe new springs too if they are mushy.

[74NovaMan]

Your upper control arm bushings look ready to be replaced... whenever you get around to it. I didn't replace mine 'til the rubber fell out and it started clunking - though they didn't look as bad as yours do. :D

I did not even notice that. Thanks for pointing it out. I'll add that to the list for when I get drop spindles.

[yellomalibu]

A lot of those under-hood shots look eerily similar to my truck.
The valvetrain is much cleaner than mine was when I got it. Several years of running high detergent oil and running a quart of Marvel through it a day before an oil change have it looking about as good as yours is now.
Your upper control arm bushings look ready to be replaced... whenever you get around to it. I didn't replace mine 'til the rubber fell out and it started clunking - though they didn't look as bad as yours do. :D

[DanStokes]

Only notable was that the upper radiator hose connection was smaller than the hose by a significant amount. The hose looked to be a size or two larger than it needed to be to fit properly. I looked at the old hose and it looked like that one had the same issue but it had clearly been on there a while so I clamped the new one down with a new clamp and called it good. I suspect that the radiator is probably a replacement and that the inlet is not the correct size.

It's a pretty common deal. The new, big radiator in the Volvo has 1 1/4" connections top and bottom while the Mustang hoses are 1 1/2" at the t-stat (got lucky on that as the Mustang hose reduces to 1 1/4") while the lower hose is 1 3/4 out of the water pump but immediately reduces to 1 1/2". The original installer just clamped the 1 1/2" down on the lower connection (the radiator I pulled out also had 1 1/4" up and down). I had this sort of situation on my Vega/Buick conversion and I went to the local radiator shop and they had a reducer, just a sleeve, that slid over the radiator neck and made it the bigger size. Turns out that this is a standard part from Dayco, Gates, etc. though our local parts guys couldn't get them for whatever reason. A trip to <Summit Racing.com> turned up a set with 1 3/4" to 1 1/2" and 1 1/2" to 1 1/4" in a kit for like $7 or so - cheap. Summit PN 390003 and I've also seen them online. Makes a nice, clean job of it.

Dan

[74NovaMan]

If I did it at all, I'd put just enough anaerobic goop on it to hold it in place against the pan (very little).

oh - I'd make sure the trans body and pan were spotless and flat, but you already do that... just thought I'd mention it.

Thanks Beagle. I think I found a cork gasket kit at NAPA. I usually hit the surfaces with wax and grease remover as well before gasket install after everything is spotless.

[Beagle]

Technical Question:

When installing a rubber trans pan gasket, do you (or would you) use and gasket maker or sealant? I've always thought no, but the parts guy recommended Permatex Ultra Grey. I'd honestly prefer cork so I can put 3M Gasket Adhesive on it. I'm having some difficulty sourcing a trans filter kit locally that has a cork gasket.

If I did it at all, I'd put just enough anaerobic goop on it to hold it in place against the pan (very little).

oh - I'd make sure the trans body and pan were spotless and flat, but you already do that... just thought I'd mention it.

[74NovaMan]

Technical Question:

When installing a rubber trans pan gasket, do you (or would you) use and gasket maker or sealant? I've always thought no, but the parts guy recommended Permatex Ultra Grey. I'd honestly prefer cork so I can put 3M Gasket Adhesive on it. I'm having some difficulty sourcing a trans filter kit locally that has a cork gasket.