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Rear end ratio with a question
https://www.slantsix.org/forum/viewtopic.php?t=31711		 Page 1 of 1
Author:  Scamp [ Wed Oct 15, 2008 4:07 pm ]
Post subject:  Rear end ratio with a question
This may be a stupid queation, BUT. I am not a mechanic. My 1971 Plymouth Scamp has a posi rear end. It makes a noise when you change the speed by going down on the gas pedal or letting up on it. Maybe a pinion bearing???? I found an other Scamp that was set up with a V8 motor. Mine is a slant six. The parts car is setting down where I can't see what rear end it has. My question is: If this car was a V8 would it have a larger ratio rear end that would make my car go easier at higher speeds? That would be my only lead to changing rear ends. Thanks Ping
Author:  dakight [ Wed Oct 15, 2008 4:49 pm ]
Post subject: 
What kind of noise?
Author:  Scamp [ Wed Oct 15, 2008 6:11 pm ]
Post subject:  Rear end noise
Its a whinning noise that changes as the speed increases or decreases. Thats the best that I can do in explaining it. Ping
Author:  volaredon [ Wed Oct 15, 2008 7:53 pm ]
Post subject: 
Sounds like you are describing the "hum" that every SURE GRIP vehicle I've ever had, has done; On the ratio, chances are that whether a /6 or V8, the ratios could very well be identical. What are you wanting out of YOUR car? MPG? EZ Burnouts? hiway cruiser? is it an in town, never sees the open road type? has the engine been modded (cam, etc) theres more to picking a gear than "/6 or V8".
EDIT; How do you know that you have a Sure Grip (GM and Mopar are not the same Co---- yet, anyways) Posi is a GM name.

Also what do you mean "go easier" down the highway; does the engine seem to run "too fast" for a given road speed? Does it not want to get up to the speed you are wanting it to go? Or does it seem like the engine is "lugging"? Is the engine running the best it possibly can? If the answer to this question is NO, then get the engine into the best possible state of tune; that will definitely help; being a 71 it may well still have points. (if someone has not switched it over from orig equipment) Burnt or maladjusted points, timing issues, timing advance, carb tuning issues can all make the car "struggle". Like I said we need more info to help. THEN look further into gar ratios, tires, etc.
Author:  Scamp [ Fri Oct 17, 2008 8:01 am ]
Post subject:  Rear End
Quote:
Sounds like you are describing the "hum" that every SURE GRIP vehicle I've ever had, has done; On the ratio, chances are that whether a /6 or V8, the ratios could very well be identical. What are you wanting out of YOUR car? MPG? EZ Burnouts? hiway cruiser? is it an in town, never sees the open road type? has the engine been modded (cam, etc) theres more to picking a gear than "/6 or V8".
EDIT; How do you know that you have a Sure Grip (GM and Mopar are not the same Co---- yet, anyways) Posi is a GM name.

Also what do you mean "go easier" down the highway; does the engine seem to run "too fast" for a given road speed? Does it not want to get up to the speed you are wanting it to go? Or does it seem like the engine is "lugging"? Is the engine running the best it possibly can? If the answer to this question is NO, then get the engine into the best possible state of tune; that will definitely help; being a 71 it may well still have points. (if someone has not switched it over from orig equipment) Burnt or maladjusted points, timing issues, timing advance, carb tuning issues can all make the car "struggle". Like I said we need more info to help. THEN look further into gar ratios, tires, etc.



Yes, Sure grip is the term. I told you I am not a mechanic. Only know I do like Chrysler Products. I had a new 1966 Plymouth Fury III with the sure grip. No whine to that. The whine is what I am worried about. The only reason for changing the rear end would be I don't need sure grip to run in the summer months and I have the rear end avialable and thought it might be cheaper to change the rear end than to try to get the howl out of the sure grip. I am restoring this car in hopes that I will drive it to Florida one winter soon. this not being the winter. Its not the speed so much as it is running at a lower rate for the motor. It is the slant 6 225 engine. They tell me it had been re done not long ago. It doesn't idle good. The minute you get it rolling it seems to straighten out and runs good. Re built carb, wires, plugs and all the vaccum is also new. I am at loss for the poor idle........The dist hasn't been changed over. Maybe in the spring, I should try that. ???? Thanks for your imput. Ping
Author:  Doc [ Fri Oct 17, 2008 10:21 am ]
Post subject: 
My bet is that the poor idle is caused by mis-adjusted valve lash.
Most SL6 engines have solid lifters which needs careful lash (clearance) settings. Today, most engine rebuilders and mechanics do not know how to do this setting correctly and it is often the cause of poor idle quality.

As for your rear end "howl", is the gear oil level OK? Has the unit ever run low on gear oil?
DD
Author:  Scamp [ Fri Oct 17, 2008 5:01 pm ]
Post subject: 
Quote:
My bet is that the poor idle is caused by mis-adjusted valve lash.
Most SL6 engines have solid lifters which needs careful lash (clearance) settings. Today, most engine rebuilders and mechanics do not know how to do this setting correctly and it is often the cause of poor idle quality.

As for your rear end "howl", is the gear oil level OK? Has the unit ever run low on gear oil?
DD
That is something to think about with the valves. That very well could be the case. I don't think the fellow that had the car knew just what he was doing in some cases. I know just enough to be dangerous in mechanics. Been around it all my life, but my father didn't have the patience to teach me. So, What I know I have picked up on my own working on my own vehicles. As far as the oil in the rear end. I just bought the car this past summer. I have driven it about 1600 miles. That howl was there when I bought the car. Doesn't seem to be any different than it was the first mile that I drove the car. May I ask where you are writing from? I am in central Maine and on my way to Florida in a couple of days. We will be there for the winter months. Then back to Maine to work on the Scamp once again. From what you know, would the pinison bearing being rough make the howl and change pitch when pressing down on the gas or letting off? Thats just a guess on my part. On a positive note, I have been looking for a set of Rally wheels for my Scamp. I found a set today. They have been hard to find. I didn't like the hubcaps that came on the car. Looked like a chinese hat to me. :)
Author:  volaredon [ Fri Oct 17, 2008 6:08 pm ]
Post subject: 
I'm in Illinois and its impossible to hear the noise you talk about from this distance (I'd hve to ride in it) but the last couple Sure grips I had did what I believe that you are talking about; but again cannot tell for sure; yes a bad bearing can definitely cause a howl as can scored gears. My suggestion? Drive it; keep an ear to it and if you notice any change in it (pitch, change in speeds, lane change or corners make difference, where maybe they do not now, etc) then worry about it; the fact that you say it has not changed since "Mile 1" of your ownership tells me itcould be nothing to worry about; Me? If I did determine that there is actually a problem, as long as it is just a bad bearing or if you have a seal leak (I know that won't cause a noise but is a common rear diff problem) I'd be inclined to fix what i had; the donor rear may be worse off! Its when you get into carriers, gears, and having to pay flat rate to have it done for you is where it gets costly; Be Sure there is actually a "problem" to be fixed before you tear into something like that; Tires can cause a howl/hum; and the A bodies were not known as having the best insulation
of the line as they were "economy" cars; just like with the B vans; any "noise" is amplified in any that were cargo vans and not conversions. (no carpet/padding/insulation)
Author:  Charrlie_S [ Fri Oct 17, 2008 6:27 pm ]
Post subject: 
Quote:
I am in central Maine and on my way to Florida in a couple of days. We will be there for the winter months.
What part of Florida are you coming to. I live in north central (Ocala area).
We have some big car shows/swap meets this time of year
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