Joined: Tue Mar 12 2013, 11:31AM
Location: Germany
Posts: 70
I am considering to change my rear axle gears. Now I read about gear vendors overdrive. with the on/off switch you don't just get a 4th gear but you get 6 gears. I just copy the ratios from hotrod.com:
Gear Ratio Chart: Torqueflite 727
Axle Ratio 4.88 4.56 4.10 3.55 3.23 2.76 Trans Ratio Final Drive Ratio 1st 2.45 11.9611.1711.058.69 7.91 6.76 1st Over 1.91 9.33 8.71 7.84 6.78 6.17 5.27 2nd 1.45 7.08 6.61 5.95 5.15 4.68 4.00 2nd Over 1.13 5.52 5.16 4.64 4.01 3.65 3.11 3rd 1.00 4.88 4.56 4.10 3.55 3.23 2.76 3rd Over 0.78 3.81 3.56 3.20 2.77 2.51 2.15
Would that be smart? and if, should I go lower than 3.55?
Joined: Tue Mar 12 2013, 11:31AM
Location: Germany
Posts: 70
I don't want to change the final drive. I want to change the gear ratio in the rear axle to get a better acceleration. but with that the engine will rev up pretty fast. That would make an overdrive a good choice. But with te GV you don't just get one extra gear but (if you switch it on) 3 extra gears. so the gap between the gears os not that big and (as I understand) the accaleration gets better AND the engine wouldn't rev up that much
Joined: Sat Aug 19 2006, 05:03PM
Location: Ontario, Canada
Posts: 2919
FYI, you only get the intermediate gears if you shift manually and shift the GV on and off manually at the same time. If you have the GV in Auto, its computer controls just engage it when you get to a certain road speed, so it acts as an overdrive 4th gear.
Joined: Tue Mar 12 2013, 11:31AM
Location: Germany
Posts: 70
I know that. That's perfectly fine, since I don't race every 10 minutes.
But my question was (and is) if it is smart. I read that theres no good overdrive transmission for big block engines. But I want to change the rear axle ratio. So an overdrive would be good for the mpg and the engine. The intermediate gears would just be an extra. But an extra that is for the good of my goal (better street performance).
Joined: Thu Mar 22 2007, 08:13AM
Location: In the workshop
Posts: 1063
rage607 wrote ...
... I read that theres no good overdrive transmission for big block engines. But I want to change the rear axle ratio. So an overdrive would be good for the mpg and the engine. The intermediate gears would just be an extra. But an extra that is for the good of my goal (better street performance).
First, dont believe everything you read. Theres are a few on here that successfully use the GV, including myself. There are also a few that use another solution.
Second, the rear axle ratio is the final drive.
Thirdly. I realise that for you, writing in english is writing in a foreign language, but try to be more polite in your answers. Also, do a bit more research before you ask the questions.
Joined: Tue Mar 12 2013, 11:31AM
Location: Germany
Posts: 70
If I was unpolite, I apologize. I thought you meant, that I want to change the ratio in the transmission. I didn't know that you meant the rear axle (I now did the math, that the third gear is 1:1 so it is the the rear axle ratio = final drive). Sorry about that. I also don't use sarcasm or irony because written down no one would get it. So if something sounded sarcastic or something, it was not meant like that.
But I do have to say, that I use this forum for reasearch because I don't know the good american sites. What I find are truck, mustang or corvette drivers. But I think, that you guys know better because you drive the same 2 ton whales across the streets like me.
I also might be a bit obtrusively (I hope that's the word) with my questions. That's because I want to make my plans with your opinions and experiences in mind, before I buy that stuff and everything is wrong.
And that brings me to your first sentence. I don't believe what I read on the internet (especially not, what the manufacturer says). So I ask you guys. You guys live where the cars were built. You guys have more experience with those cars and with parts that special. I could ask anybody here and I would be lucky if I would find just one guy with a GV overdrive (or even one who changed his gear ratio).
Everybody here is like: whoa dude, I got a 5 Liter Big Block... look at it. (that is really not sarcastic) I don't have to say that no one drives full size cars (maybe a riviera).
this forum is so specialised, it is like wonderland for me.
We have a shop here just for mopars. Everytime I want something special to a c-body: nothing. No control arms, no steering parts, no knowledge if that header or that part would fit. Maybe it is not the right thing to do, but I rely on you guys.
And in every threat I write an honest "Thank you". And I really mean it. Sure some people have a big closet full of "thank you"s. But that's all I can give. If I the day comes and someone asks something just I know, I will be there and help with happieness.
Sometimes we lose sight of the fact that not every one has been doing this for a long time or is familiar with these cars.Ask away,most here will be glad to help.
Joined: Sat Mar 04 2006, 08:01PM
Location: Tucson AZ
Posts: 171
Rage607, you were perfectly polite. I don't see how Uncle Joe could read otherwise.
There are many options for an automatic with overdrive that will work with a big block Mopar. Despite what you may have heard/read, the A518 transmission can be made to run very reliably behind a BB. It's not the best choice in a full race application (as it robs HP) but then neither is any other auto OD transmission. There are also GM transmission swaps many have used successfully including the 700R4, 200R4, and 4L80E. All of these transmissions will require modifications to run, from transmission cross members up to modifying the transmission tunnel, and have their pros and cons. There is a lot of info on putting any of them behind your BB. The info will be the same for hooking them up your engine so read up on each one of them. The only differences will be chassis related like cross members, exhaust, and transmission tunnels mods.
Lastly, there are also quite a few manual transmissions with OD that will work as well. I personally don't know about those so, if you're interested, I'll let someone else with more knowledge on them inform you about the options.
If you first spend the money to change to a Rear Axle 3.2:1 Final Drive Ratio --- you may never have any more thoughts of what you have asked about with The Gear Vendors Over-Drive.
This is the same unit that is used with The Factories Performance Package, Police Package, Tow Package and etc - etc .
Because of this ratio - the engine does not "work" as hard to move The Mass from 0 to The Posted City Speeds. Once out on The Auto Bahn it also permits you to have a very strong Traffic Speed when you are in a Open Area.
( remember the suspension is best designed for a Max Speed of under 120 MPH )
You are in a vehicle marketed for people of better than average means, who can carry a car load "of nicely dress stiff shirts" --- not a Ralley Want Ah Be.