GV unit causes the trany to overheat??

[green69rt]

I was reading thru some threads on this site and came across one that talked about a GV unit causing the trany to cook at low speeds.  Is this a cause for concern?  I've thought about getting one for mine (3.91 rear.)   But now just thinking that it may be better to just swap gears when I go cruising. 

I've always believed in dedicated transmission coolers and deep sump, finned transmission pans.  Is that enough to solve the problem with the GV unit?

[RECHRGD]

I've never had a problem with the tranny getting hot.  I only use it at highway speeds though.  I suppose if you used it at low speeds there MAY be an issue, but it is supposed automatically turn off at 40mph anyway.......

[303 Mopar]

Watch this video installation by Roadkill on their Super Bee.  GV warns against running the OD under 30 mph and in Reverse.  These are only allowed in Manual mode, Auto mode only engages in 3rd OD.

https://www.youtube.com/watch?v=SywsCGnoXOU&feature=youtu.be

[c00nhunterjoe]

I would imagine the converter slippage backed by the gear ratio causes the heat. I dont know why you would want overdrive in reverse or slower the 30 mph anyway? My car with 4.88s doesnt even need overdrive at 30 mph. 

[Kern Dog]

Reverse???!!

The GV I had was an older unit that was rebuilt when the prior owner ran it several hundred miled with NO oil in it...
Mine worked great and never caused the ATF to look or smell burned. The control box was a little kooky though. It would sometimes keep the trans in OD at all times. Try hammering the car from a stop in OD, effectively your 3.91 gear car is now a 3.05. It sorta takes the punch out of your launch!  
The wiring and control box was one of the early styles. The story is that they are designed to engage at 46 or so mph and then disengage below that but my operating switch allowed me to use OD at any time. I never tried reverse at any crazy speed.

[green69rt]

Some useful info, thanks to all.

[John_Kunkel]

I would imagine the converter slippage backed by the gear ratio causes the heat.

Yep, same problem with hi-stall converters and numerically low axle ratios, the converter is still slipping at lower road speeds and builds heat.

[flyinlow]

For what it's worth.

440 Charger with 518A trans. 3.55 axle.

I was driving home one summer night 200 mile drive on the freeway at 70mph. Big plate cooler and a deep pan. Transmission 0.69 OD makes the 3.55 axle seam to be about a 2.45 . Temp gauge in the pan stabilized about 140* in overdrive and lock up ( 0% converter slip). I flipped the switch and un locked the converter.  The rpm went up about 300. The trans. temp re stabilized about 20* warmer . Mostly from the 10-15 % converter slip I assume 

Low speeds with a tall overall top gear ratio can make the converter slip a lot.

[Kern Dog]

Was ther a lot of cutting to fit the 518 in the Charger? I would really like to do this but I hate the idea of cutting into the torsion bar crossmember.

[cdr]

For what it's worth.

440 Charger with 518A trans. 3.55 axle.

I was driving home one summer night 200 mile drive on the freeway at 70mph. Big plate cooler and a deep pan. Transmission 0.69 OD makes the 3.55 axle seam to be about a 2.45 . Temp gauge in the pan stabilized about 140* in overdrive and lock up ( 0% converter slip). I flipped the switch and un locked the converter.  The rpm went up about 300. The trans. temp re stabilized about 20* warmer . Mostly from the 10-15 % converter slip I assume 

Low speeds with a tall overall top gear ratio can make the converter slip a lot.

I have 512 & a518, took out the 3.91 & now have 3.23, I also have lock up converter, great street combination.

[Mike DC]

Was ther a lot of cutting to fit the 518 in the Charger? I would really like to do this but I hate the idea of cutting into the torsion bar crossmember.

Remember that physically bolting the A518 under there is only part of the story.  It needs to fit with enough clearance for vibration & engine torque, and still have decent driveline angles, ground clearance, etc.  The amount of cutting "required" will probably vary depending on the builder's idea of a streetable setup.

IIRC the overdrive version already starts out with a 1" deeper fluid pan (and valvebody inside) than the old 727s.  So that's an inch of ground clearance lost even if you get the A518's tailshaft to sit exactly the same height as the original.  




Having said that, I think even the Gear Vendors swap sometimes needs some whacks against the tunnel.  

[flyinlow]

 The Charger is a '73 so it has a separate T bar and trans. crossmembers. Minor body fitting, major mod to trans cross member. Tail shaft is same place as the 727 was as far as distance from the floor , but 3.5 inches farther to the rear.

After having OD for 30K.+ miles  , I would cut the entire floor out , install a sun roof and sit on a milk crate to make room for it if I had to.

[Kern Dog]

I had a GV for a couple of years. I wished that I'd had my 2 post lift at the time to be able to see everything from a better perspective. Laying on the concrete looking up sucks as compared to standing and looking at underbody stuff.  I must have had the unit too low because the GV unit was still 1/2" or more from the trans tunnel. I measured the distance of the floor pan to header collector as a reference, then with the GV in place, I modified the crossmember to get the same clearance. The car was on jackstands and the front of the car was higher than the rear. A torpedo level on the trans pan wouldn't have helped.
If I had a GV today, I could certainly get any kinks worked out with it. These 2 post car lifts are fantastic.