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  #1  
Old 07-15-2022, 03:33 PM
devildog80's Avatar
devildog80 devildog80 is offline
258 I6
 
Join Date: Apr 13, 2022
Location: Apache Junction AZ
Posts: 328
OVERDRIVE - BOLT ON - AFTER MARKET

Thread for general information as I had the thought to find one for my rig.

Overdrive unit available (for hiway OD only-which is what I want) bolts on back of the existing TC, requires a new rear only drive shaft, and turns the 727 3-speed into a 6-speed.

The bolt on unit electronically shifts in manual or auto shift mode with 1/2 gear increments, to the full gear shift of the auto trans.

So your 3-speed will shift like this
1 to 1-1/2 to 2 to 2-1/2 to 3 to 3-1/2

This is the site for Dodge 727 3-speed info
Dodge 3-Speed Auto - Gearvendors

Go here for more info-
info@gearvendors.com

Looks like the bolt on unit is right at $3200, then need shorter rear drive shaft, as unit is about 12" thick.

Best part about it, they have an exchange program so when you change vehicles, you get credit for exchange to different unit.

Units handle up to 1200 hp, then need hydraulic modification up to 2000 hp.

Looks promising....just need to find those money tree seeds and get that sucker growing

Honestly....would rather spend this kind of money for an O/D unit, rather than FI.
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'81 CJ5 Base, 258 I6, MC2100, T176 4 spd, 300 TC, D30 Front NT, 3.31, 2-Piece AMC 20 rear NT, 3.31, 4" high arc spring lift

'84 Grand Wagoneer, 401 V8 (.030 over), MC2150 HA Comp, 727 auto, Selec-trac NP229, AMC 20 REAR - D44 FRONT - WT 3.31, 4" high arc spring lift

Rather be driving, than waiting to be modified
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  #2  
Old 07-16-2022, 07:09 AM
wiley-moeracing wiley-moeracing is offline
350 Buick
 
Join Date: Feb 15, 2010
Location: arizona
Posts: 1,429
If you are doing this to save gas, it is not worth it, that $3200 will buy a lot of gas over the years, not to mention your labor and other parts needed to do the install. You could do a transmission swap that has a overdrive in it also.
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  #3  
Old 07-16-2022, 10:56 AM
devildog80's Avatar
devildog80 devildog80 is offline
258 I6
 
Join Date: Apr 13, 2022
Location: Apache Junction AZ
Posts: 328
Not to save gas, as there are still a lot of dead dinosaurs down there for me to burn through, but I like the reputation of the 727 transmission. Thinking the O/D would just make it nicer to drive for towing on the road, and if I save gas in the process, ok.....and working on that angle separately.

We currently are using my dads 16 ft Scamp camper, which the GW will be pulling when ready, which is less weight than most flatbed trailers empty.

So when I get the GW road worthy and driving, will see how it performs, and where improvements are needed.

Seems as with most add on devices for these old rigs, to make them more like our modern vehicles we are spoiled with, anything costs thousands of dollars. At the stage of my build, watching what everyone else is doing, to try and get my money best spent when the time comes.

Thanks for feedback, and keep burning the dinosaurs
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'81 CJ5 Base, 258 I6, MC2100, T176 4 spd, 300 TC, D30 Front NT, 3.31, 2-Piece AMC 20 rear NT, 3.31, 4" high arc spring lift

'84 Grand Wagoneer, 401 V8 (.030 over), MC2150 HA Comp, 727 auto, Selec-trac NP229, AMC 20 REAR - D44 FRONT - WT 3.31, 4" high arc spring lift

Rather be driving, than waiting to be modified
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  #4  
Old 07-16-2022, 01:58 PM
wiley-moeracing wiley-moeracing is offline
350 Buick
 
Join Date: Feb 15, 2010
Location: arizona
Posts: 1,429
Ideally, a different trans with the overdrive in it and a lock up convertor and changing gears in the diff to 373 will make it more enjoyable to drive. Something I may get around to one day.
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  #5  
Old 07-18-2022, 08:48 PM
fastjeep fastjeep is offline
232 I6
 
Join Date: Nov 20, 2009
Location: York PA
Posts: 42
Have a 6L80 trans from late gm, bolted to a 208 transfer. Only 1.5 inches longer than 727/208 with Advance Adapter to 360. With a 4.02 1st gear and 2 overdrives will drop cruise rpm's about 1400. My J10 has 4:10 gears with 33" tires so current cruise rpms about 3400. Will have about $2600 in parts to convert. I figure with that 1st gear ratio will help towing starts also.
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  #6  
Old 07-19-2022, 06:33 AM
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Mikel Mikel is offline
 
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Location: New Haven, CT
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Quote:
Originally Posted by fastjeep
Have a 6L80 trans from late gm, bolted to a 208 transfer. Only 1.5 inches longer than 727/208 with Advance Adapter to 360. With a 4.02 1st gear and 2 overdrives will drop cruise rpm's about 1400. My J10 has 4:10 gears with 33" tires so current cruise rpms about 3400. Will have about $2600 in parts to convert. I figure with that 1st gear ratio will help towing starts also.

Hi - How do you plan on controlling the 6L80?
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1963 J300 Swivel frame
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  #7  
Old 07-19-2022, 08:38 PM
fastjeep fastjeep is offline
232 I6
 
Join Date: Nov 20, 2009
Location: York PA
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Zero Gravity Performance has a controller for the trans, needs a tach signal and an TPS to use.
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  #8  
Old 07-20-2022, 12:43 PM
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devildog80 devildog80 is offline
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Join Date: Apr 13, 2022
Location: Apache Junction AZ
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So if I do not have a TPS on my '84 GW, I would need to install one just to use this O/D?
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'81 CJ5 Base, 258 I6, MC2100, T176 4 spd, 300 TC, D30 Front NT, 3.31, 2-Piece AMC 20 rear NT, 3.31, 4" high arc spring lift

'84 Grand Wagoneer, 401 V8 (.030 over), MC2150 HA Comp, 727 auto, Selec-trac NP229, AMC 20 REAR - D44 FRONT - WT 3.31, 4" high arc spring lift

Rather be driving, than waiting to be modified
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  #9  
Old 07-20-2022, 08:38 PM
fastjeep fastjeep is offline
232 I6
 
Join Date: Nov 20, 2009
Location: York PA
Posts: 42
Yes you can install one on throttle linkage. I have Fitech injection and they have patch cables avaliable to operate 4L80 trans as so do Sniper and other throttle body injections do. Most are looking into getting able to do the 6L80 trans but not made jump yet. To use NP208 transfer must install 32 spline input gear to match trans output spline. There are 3 different output shafts on the 6L80 trans, a 2wd slip yoke, a 4wd shaft out of truck and a fixed yoke 2wd. I used the 2wd fixed yoke that requires some modification to shaft and install 2 small plugs in rear case to seal trans fluid from tail housing and a shaft seal that Advance Adapters has a kit to do. One thing that can be done also with the trans controller is a kit to do paddle shifter on steering wheel which I am thinking of doing.
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  #10  
Old 07-21-2022, 11:57 AM
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devildog80 devildog80 is offline
258 I6
 
Join Date: Apr 13, 2022
Location: Apache Junction AZ
Posts: 328
Wow....way too much modernizing for my taste.

Just a simple mechanical auto w/OD!
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'81 CJ5 Base, 258 I6, MC2100, T176 4 spd, 300 TC, D30 Front NT, 3.31, 2-Piece AMC 20 rear NT, 3.31, 4" high arc spring lift

'84 Grand Wagoneer, 401 V8 (.030 over), MC2150 HA Comp, 727 auto, Selec-trac NP229, AMC 20 REAR - D44 FRONT - WT 3.31, 4" high arc spring lift

Rather be driving, than waiting to be modified
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  #11  
Old 07-21-2022, 04:01 PM
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Mikel Mikel is offline
 
Join Date: Aug 09, 2000
Location: New Haven, CT
Posts: 6,330
Quote:
Originally Posted by fastjeep
Zero Gravity Performance has a controller for the trans, needs a tach signal and an TPS to use.

Thanks
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1963 J300 Swivel frame
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