Slant Six Forum
https://slantsix.org/forum/

Rear end change? Need lotsa help!
https://slantsix.org/forum/viewtopic.php?t=17726		 Page 1 of 2
Author:  RossKinder [ Thu May 25, 2006 7:05 am ]
Post subject:  Rear end change? Need lotsa help!
1965 Valiant:

Being in an area where Mopar has always been a missing word (no Mopar transmissions in the junk yards), I'm think about changing the rear end ratio as a way to get to something near overdrive highway performance. Horrible idea?

I've never had occasion to change _any_ rear ends - only axles. How much is involved? Can one merely swap out ring and pinion? Or does it require a complete change of what my dad always called the "chunk?"

Might one do as well swapping out the entire rear end, housing and all? (That could get me out of the 4 inch circle/13 inch wheel category, maybe even help with brakes.)
Author:  CrAlt [ Thu May 25, 2006 4:17 pm ]
Post subject: 
What gears are in it now?

If its got something like 2.76's in there then going any higher then that will just make the car a slug at low speeds.

If its got 3.23's in it then it might be easyer to hunt down a 2.76 rear then swaping the ring/pinion.
Author:  RossKinder [ Thu May 25, 2006 4:32 pm ]
Post subject: 
Quote:
What gears are in it now?
Being stock stick 225, I assume it's 3.23. It revs quite a bit when I get up to highway speeds, and shows no mercy at the gas pump.
Quote:
If its got something like 2.76's in there then going any higher then that will just make the car a slug at low speeds.

If its got 3.23's in it then it might be easyer to hunt down a 2.76 rear then swaping the ring/pinion.
Now there's the rub. As I tried to indicate by my question, I don't know the difference between swapping a 2.76 and swapping a ring and pinion.

And as I also tried to indicate, if swapping a 2.76 means the whole rear end, axle housing and all, that's essentially impossible in this non-Mopar, aggresively GM area. Thanks
Author:  69valiant [ Fri May 26, 2006 5:07 am ]
Post subject:  rearend swap
A few weeks ago, I swapped out my old, tired, leaking, stock 7 1/4 rear end in my 69 Valiant with a more solid 7 1/4 that I got from a friend. Anyway, not knowing much about grar ratio's and the such, whatever is in this new one has made a marked improvement on the highway. I know the speedo guage isn't right, but going 60 mph by the guage I'm actually going 68-69mph. One of those radar detection things on the highway that advises you of your speed showed me that. I can tell that the engine isn't working as hard to get me up to that speed. I'd call that an improvement. Anything to make the motor not have to work as hard is good for me. Also, I threw on 14" tires instead of my old 13's and it feels even better. Sorry, I can't tell you what ratio's they are, but it seems to be a good thing.
Author:  Doctor Dodge [ Sat May 27, 2006 8:19 am ]
Post subject: 
Quote:
If its got 3.23's in it then it might be easyer to hunt down a 2.76 rear then swaping the ring/pinion....

Now there's the rub. As I tried to indicate by my question, I don't know the difference between swapping a 2.76 and swapping a ring and pinion.

And as I also tried to indicate, if swapping a 2.76 means the whole rear end, axle housing and all, that's essentially impossible in this non-Mopar, aggresively GM area. Thanks
The first thing you need to do is figure-out what gear ratio is currently in the car.
From there we can decide on what a "better" ratio would be for your driving needs.
Note, a high rear gear ratio on a manual shift car can be hard on the clutch, an automatic trans car has an advantage here.

As for getting a different rear, that is the way to go on this project.
7 1/4 Mopar rears can be bought for cheap and they are not hard to ship.
DD
Image
Author:  RossKinder [ Sat May 27, 2006 10:15 am ]
Post subject:  Re: rearend swap
Quote:
Also, I threw on 14" tires instead of my old 13's and it feels even better.
What is the bolt circle on your car ('69?). My '65 is 4 inches and buying 14 inch wheels for it gets up to nearly $100 per wheel from what I've seen. Thanks
Author:  RossKinder [ Sat May 27, 2006 10:47 am ]
Post subject: 
Quote:
As for getting a different rear, that is the way to go on this project. 7 1/4 Mopar rears can be bought for cheap and they are not hard to ship.
DD
OK, I'm going out on a limb here and guessing about something that has puzzled me as long as I've read this forum. When anyone uses the word "rear" they actually mean the entire rear end, brakes, axles, axle housing differential housing and differential gears in entirety, drive shaft connections, etc. Right?

Getting the answer to this would tell me exactly what you meant by "hunt down a 2.76 rear."
Author:  mcnoople [ Sat May 27, 2006 11:46 am ]
Post subject: 
The only chrysler rear axle with a removable center section (pig,chunk, etc) is the 8.75 axle. Since the 7.25, 8.25, and 9.25 were all 1 piece assemblies if someone mentions hunting down a rear end they more likely than not mean a complete assembly.
Author:  Joshie225 [ Sat May 27, 2006 12:54 pm ]
Post subject: 
Ross,

Most people don't swap ring and pinion gers in the Salisbury rear ends. It takes some special tools and experience to do so. Read your factory service manual to see what it takes to set up a new ring and pinion. If you don't have a FSM you need one. It will answer many questions you have and you will be better for the experience.

When folks say "the rear end" they mean the whole rear axle assembly usually with the brakes. For instance I am going to pull the rear end out of a '76 Duster to swap into a '67 Valiant so that the car has the bigger 4.5" bolt pattern for the wheels as well as 10" brakes. They are both 7 1/4 rear ends so they bolt right in place of one another.
Author:  RossKinder [ Sat May 27, 2006 4:35 pm ]
Post subject: 
Quote:
The only chrysler rear axle with a removable center section (pig,chunk, etc) is the 8.75 axle. Since the 7.25, 8.25, and 9.25 were all 1 piece assemblies if someone mentions hunting down a rear end they more likely than not mean a complete assembly.
Thanks.
Author:  sandy in BC [ Sat May 27, 2006 8:34 pm ]
Post subject: 
Its not hard to swap gears in a 7.25 axle if you have some mechanical experience....I put my 3,23 gears from my 65 rear into a 75 rear when I swaped axles to get BBP and 10" brakes. That being said , swapping the entire unit is much less complicated (although more physical) It is far easier to swap gear sets in an rear that has been removed fom the car.

Find a rear with the gears you want, 10" brakes and BBP and you kill many birds while hardly stoned.
Author:  RossKinder [ Sun May 28, 2006 6:49 am ]
Post subject: 
Quote:
Find a rear with the gears you want, 10" brakes and BBP and you kill many birds while hardly stoned.
OK, it took a while searching, but I finally learned that BBP means big bolt pattern, and that seems to require 1973 or later.

1. Is there any kind of reference to know what gears were on which cars?
(Hm, probably automatics have the shorter ratios, but...)

2. Do all A-bodies have the same distance between spring pads?

3. Is there any likelihood that one could find a stick tranny with a longer bottom ratio? (Maybe from a 170?)

4. What would be the "ideal" auto tranny to install into my stick '65 Valiant?

5. They didn't make stick '65s for highway mileage did they?

Thanks
Author:  Doctor Dodge [ Sun May 28, 2006 7:23 am ]
Post subject: 
If your 65 Valiant has a "3 on the tree" manual trans, my guess is that it has a 3.23 rear end ratio. There is a possibility that it is a 3.55
Get under the car and look for the ratio number stamped into the housing flange.

Those 3 speeds do have a low first gear ratio so you could most likely go with a 2.93 rear ratio without much problem. A 2.76 ratio would be tough on the 9 inch clutch.

Just as a ref, I could sell you a 2.93 SBP 7 1/4 rear end assembly and throw-in a couple of SBP 14 inch wheels for right around $100.00 plus shipping. This is the least expensive way to get the improved freeway milage you are after.
Drop me a PM if interested.
DD
Image
Image
Author:  sandy in BC [ Sun May 28, 2006 7:23 am ]
Post subject: 
There is no reliable reference for what gears your 40 year old car may have now....look for a tag or use the old jack up one wheel method.

A body spring pad distances are consistent. I put a 75 rear in my 65...bolt in.

If you are going to switch trannies... go to a box with more gears ( 4 or 5 speed)

The easiest way to change final drive ratios is to get bigger tires.

Standard trans cars get better mileage than auto cars all things being equal.
Author:  RossKinder [ Sun May 28, 2006 10:05 am ]
Post subject: 
Quote:
There is no reliable reference for what gears your 40 year old car may have now...
Actually I was talking about hunting for a replacement rear on another car
Quote:
If you are going to switch trannies... go to a box with more gears ( 4 or 5 speed)
Will those actually give me a longer starting ratio? A place like car-part.com gives no clue one way or another if you don't know in advance which car has what - thus the need for a reference. For that matter, it would help to know what I am looking for if I'm wandering all over a yard.
Quote:
The easiest way to change final drive ratios is to get bigger tires.
With an SBP?

Thanks
Page 1 of 2 All times are UTC-08:00
Powered by phpBB® Forum Software © phpBB Limited
https://www.phpbb.com/