Thanks for continuing to consider my questions. Here's some more on my
situation.
Here's the thing: I have a perfectly good and strong TH-350 in-hand. I will
be towing a small car(on a trailer) or a boat every now and then (but a LONG
distance, and the rig might weigh 5000 pounds or a little more). As with
most pickups, it'll be empty most of the time, and when it is I'd like it to
be relatively fuel efficient and highway friendly. So I'm really looking at
a balance of hard truck use and highway travel at highway speeds.
I thought about a 700R4, but I heard they're not terribly strong, and the
installation is more complicated, and I had that good T350. Since the
engine will be a strong rebuilt, and the tranny the same, I thought it might
raise the durability factor of the rear if I upgraded or replaced it too.
Besides, running w/the T350 almost dictates very tall tire and or gear
change if I want to tach under 2800 at 60. Honestly, I've got to do quite a
bit better on the highway than 60 to stay happy.
Does anyone know just how tall and wide a tire I can fit in the stock rear
fender well? I figured the largest stock unit of 17x7.5 had to be close to
33.5 inches high. That's a mighty skinny tire to be driven by a 300HP 8. I
can run a 32.8" tire (255/85 R16) on my 16" rims and get pretty close to
stock height w/good width. But with the 4.56 I figure I'll be taching 2878
rpm. Is that too high??? I don't have enough experience w/V8s to know. At
70, I'd be taching around 3360. Can I run a 350 like that for 400 miles?
How about 2000 miles?
By the way, I found an incredibly good website for these gearing questions:
http://www.ring-pinion.com/home.html
Click on the Calculators link at the bottom.
Gary Perry recommended the 3.90 rear I can get from Randy's if I'm towing.
(It was the highest gear they have available.) I may go that route. What
happens if I find a 3.20 whole rear out of an old suburban and tow hard with
it? Does the engine bog? Will something just break?
Mainly, I'm guessing its best to keep the revs down as low as possible for
fuel economy, but need a little rev for power if towing. Randy's site says
1800-2800 at 60 is recommended. I can't quite do it with the 4.56 but might
try it for a while.
How high can a more or less stock 350 rev and still get decent fuel economy?
I'm rambling, so....
Jeff
'50 3600
-----Original Message-----
From: John Martinez [mailto:jsmartnz@cwnet.com]
Sent: Monday, January 21, 2002 10:42 AM
To: dnoyes@pacbell.net
Subject: Subject: [oletrucks] 50 3600 REAR END SWAP
I have a '50 3/4 ton with a 4.56 rear end. I'm installing a 350/T350 and
need to change the rear for highway cruising. I would like to only replace
the ring & pinion, but the best I could find was 3.90. I'm looking for more
like 3.20 or better.
I am not sure if they will fit but I do know that the ring and pinion from
an auto
in 56 is 3.26 ratio. in a 10 bolt rear end. I was never happy with it since
I
had it on a 56 with a close ratio 3 speed manual. I could go to 90 mph in
second gear!
Have you given thought to just doing a overdrive unit?
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