3 speed with overdrive or 5 speed manual

Guest · Post by **Guest** » Tue Jun 22, 04 7:35 am

Hi my name is Dave and I'm new to the club - I have a 68 Plymouth GTX with a 383 with 727 and a 8 3/4" rear with 3.55 gears.
I am seriously considering changing from the 3 speed 727 to a 5 speed Keisler with 0.64 or 0.82 overdrive . The other alternative is rebuilding the 727 and adding a gear vendors overdrive unit. My long term plan is to build a 500 inch big block pushing out around 600 ft/lb and 630 HP.
I want to reduce revs when cruising, and gain some resemblance to fuel economy, and also want to put the maximum power to the ground i.e. reduce parasitic losses through the drivetrain.
The car will be primarily street driven, however my main concern is that the manual may not take the abuse - Anyone got any experiences with the Keisler 5 speed?

P.S. sorry for the long winded ramblings

Dave-R · Post by **Dave-R** » Tue Jun 22, 04 8:29 am

If you read their web site I think they say what power levels they can build them to. Same with the gear vendors that I use. My worry would be the clutch on a manual with that amount of power.

Dropping the rpms will not always give you better mileage. Best mileage is at peak torque. Peak torque moves up the rpm scale with longer duration cams. So the hotter the cam you fit the lower the gears you need and the higher the rpm you need to cruise at to get best mileage.

Dave-R · Post by **Dave-R** » Tue Jun 22, 04 8:44 am

I will just give you an example of mileage.

I drove from Newcastle to York at 60-70mph to 'conserve fuel' and had to re-fill the tank at York.

After racing I set off knowing I would have to re-fuel on the way back. It was late so I ran at 75-85mph. Not only did I get back without having to re-fuel but I had plenty left over!

DHenry · Post by **DHenry** » Wed Jun 23, 04 10:03 pm

Hi Dave,
I run a gear vendors unit on the back of my 727 which is behind a 511ci RB in a 71 B body, the only problem I had was making the tunnel slightly wider (big hammer) other than that you can either let it play as three speed + o/drive or 6 speeds in semi auto and its quite good fun cos once your in your rev range you only drop half the revs when changing gear and it keeps the engine on song. When I`m cruising on only the centre carb of the six pack I can get 20 MPG . In my book best thing I did was stay auto. Hope this helps.

Regards
Dave Henry

Guest · Post by **Guest** » Thu Jun 24, 04 7:47 am

Thanks Dave and Dave
Looks like both you guys are pushing me the Gear vendor route. I was tossing a coin between a gear vendors and a 5 speed manual as I enjoy rowing the gears, but my main concern was getting the power reliably to the rear end. The Keisler TKO 600 unit is rated at 600FTlb and 650 HP however that may not include dropping the clutch at revs and drag strip duty, whereas the gearvendors is rated at 1200 HP - way more than I will ever make. Thanks for the help

Dave

Dave-R · Post by **Dave-R** » Thu Jun 24, 04 8:52 am

I made this little calculator spreadsheet so you can see what rpms you will do in each gear at various speeds.

http://www.challenger440.pwp.blueyonder ... Echart.xls

Just input your tyre size as well as your rear gear and it does the rest for you.

I have adjusted the figures to give a bit of trans slippage. Actual slippage depends on how good your converter is.

Dave-R · Post by **Dave-R** » Thu Jun 24, 04 9:56 am

If you use the Gear Vendors unit here is a WARNING.

DO NOT JUST FIT THEIR TAILSHAFT WITHOUT CHECKING OUTPUT SHAFT ENDPLAY WITH IT IN PLACE.

The trans output shaft endplay is adjusted by selecting a washer of the right thickness in the rear clutch set-up.

I just fitted the Vendors tailshaft and used the car. THIS IS A NO NO!

The circlip in the Vendors tailshaft that fits around the output shaft bearing is not in exactly the right position. At least on mine it was not.

This pulled the output shaft reawards and removed what end-play I had. The result was this.

Dave-R · Post by **Dave-R** » Thu Jun 24, 04 9:58 am

That is the inside of the trans pan.

The metal came from rear of the trans case at the back of the overrunning clutch.

Dave-R · Post by **Dave-R** » Thu Jun 24, 04 10:02 am

The output shaft was pulling the inner race of the overrunning clutch into the rear of the case. It had got very hot here. The clutch had also become loose in the case which could have resulted in a failier of the clutch and a trans explosion.

After cleaning it up I drilled a hole to push pressureised oil into this area.

It was then just a case of setting the clutch back in the case and adjusting the output shaft end play again.

Everything has ran fine since.

However if I was doing this again I would use a bolt-in type rear overrunning clutch.

Dave-R · Post by **Dave-R** » Thu Jun 24, 04 10:09 am

Here is how I fitted my overdrive.

http://challenger.mpoli.fi/phpbb/viewto ... =9182#9182

You will have to register with my board to read it but that only takes a few moments. You will have to respond to an e-mail to activate your user account.

Dave-R · Post by **Dave-R** » Thu Jun 24, 04 12:24 pm

Just one more word of caution from me.

Dropping your rpms for long drives is fine. BUT dropping them below the stall speed of your torque converter is not.

The sort of power level you are talking about (630HP) will require a stall speed in the 3000-3500rpm region.

Cruising at lower rpm than that will be a waste of time because the slippage will be great your trans temp will increase and your mileage will drop.

Fitting the overdrive was one of the best things I have ever done to the car. It makes it great fun to drive. Kicking down a gear while braking with just a press of a floor switch is very useful. Being able to use a very low axle gear on the street has transformed the car. I LOVE it despite all the hassle I had.

Blue · Post by **Blue** » Thu Jun 24, 04 5:12 pm

And if any of you need a bolt in overunning clutch for a 727, I have them in stock!

Guest · Post by **Guest** » Fri Jun 25, 04 11:55 am

Thanks once again Dave. I have had a look on your Challenger website and viewed your overdrive install. There are a few quirks to getting the overdrive fitted, but nothing serious. However I have just built and fitted a stainless system with stainless flowmaster mufflers - these sit under the floorpan approximately below the front seats. I have a bad feeling that there will not be enough room between the two mufflers to fit the overdrive - so I'll be out with the angle grinder again!! You stated that I would need to use a 3000 - 3500 RPM stall converter. I take it from one of your first replies that even if I use a tighter convertor and cruise using a lower RPM with the engine I'm planning, I may not actually gain any economy as the engine will be running outside its peak torque range?

P.S. Dave Henry what stall convertor are you using and what HP is your motor putting out while still achieving 20 mpg?

Dave-R · Post by **Dave-R** » Fri Jun 25, 04 1:39 pm

I would like to know that too! I get 14mpg which I thought was good for 520hp.

DHenry · Post by **DHenry** » Fri Jun 25, 04 5:45 pm

Hi Guys,
I`m running a Hughes cam in the engine and a saturday night special TCI convertor. With the Edlebrock heads, Hughes`s recon I`d be pushing 550 - 575hp(I`m not sure how true that is?) But I must confess I`m running a 2.71:1 LSD 8.25 rear end and I have to be a bit careful. I got a 13.95 Et at 102mph at the pod last year. Dave I know how you feel with the exhaust, I had only just made up a 3" s/s X cross system and had to change the X to an H pipe when I fitted the o/drive, go for it you will enjoy the auto more. Dave whereabouts are you in Northern Iron, as I come over about 3 times ayear ,it be great to see the motor and have a few beers.

Regards
Dave Henry

Mopar Muscle Association UK

3 speed with overdrive or 5 speed manual

3 speed with overdrive or 5 speed manual

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