-------- Original Message --------
Subject: Re: [oletrucks] '56 Rear End/Tranny Change
Date: Thu, 25 Oct 2001 13:37:59 -0400
From: Kirk <kpierce@charter.net>
To: Becky Ham <the_hams@hotmail.com>
References: <F133bvQoG9Bvo93GhAU00010add@hotmail.com>
Becky Ham wrote:
>
> Need advice on whether to swap trannys or rear end. Have a '56 1/2 ton step
> side with OE front and rear suspension and axles, 283 V8 with TH350 auto
> trans. Suspect the rear end ratio is 4.11 (you could get 3.90 or 4.11 in
> '56). At 60 MPH engine RPM is 3000-3200. I'm thinking about swapping the
> 350 for a 700R4 with lockup converter. Anyone had experience or can furnish
> advice? Would appreciate any help.
>
> Carl
> '56 stepside
>
> _________________________________________________________________
> oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
I can not say about the 700R4. I do have a suggestion and a comment.
You could jack up the rear of the truck using a floor jack under the
rear end housing to lift both tires off the floor. Put safety blocks
under the axle to avoid an accident. Then mark the driveshaft and one
tire with chalk. Turn the drive shaft until the tire makes one complete
round counting the drive shaft and tire rotations. If one tire turned
one direction and the other went in the opposite direction (non posi
rear) then you will notice one of the following situations:
3.90 Your axle turned slightly less than 8 revolutions per 1 revolution
of the tire
4.11 Your axle turned slightly more than 8 revolutions per 1 revolution
of the tire.
This is because axle ratio = #revolutions of driveshaft / (2 times tire
revolutions).
Now for the comment. I have the 3.90 in my '57. I really like the 3.90
for starting off on hills and for pulling loads. I have the manual 3
speed on the column. I have added an overdrive to the muncie 3 speed by
replacing the stock tailshaft with an overdrive from a 60's chevy car.
The overdrive brought my rpm at 60 down from around 3000 to around
2200. This results in much less noise and wear. I am very pleased with
the results.
I believe your choice boils down to 1 thing. How good is the rear end
you currently run? Does it have worn shafts where the shaft runs
against the outer bearing surface? Does it wallow out seals and leak at
the wheels? Do you get lots of noise from the rear? How about the yoke
area.. any leaks or slack?
If the rear is solid I would replace the trans. If the rear is in need
of lots of work, I would replace the rear. My rear needed lots of work
and cost about 400.00 to fix. This amount does not include the cost of
the "chunk"
I got from a local salvage yard. I onlyy found one place in
Birmingham, Al. where I live that would even touch the thing.
Good luck with whatever you choose, and please post to the list what
your methods and results are. Someone on the list will find the info
valuable when they are making their decision.
PS. You will probably get lots of replies to change the tire size. I
don't think that will meet your objectives. Just my 2 cents.
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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