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700R4 into 3/4 ton Sub.

B

Brady

1/2 ton status
Joined
May 6, 2000
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Location
Parachute,Co
I have a '87 3/4 ton 4x4 Sub.Has 5.7 with the turbo 400.I believe it has 4:1 gears.Around town and on the back roads it is great.But on the Interstate it is a pig,as in gas hog!I usually drive about 70-75Mph.Using the gear cal I figure at 75 the motor is screaming at 3300rpms.
So I am thinking of swapping ina 700-R4 to get the overdrive.Figure if I can find a 1/2ton at the yards or someone parting out.I would take the trans,t-case and driveshafts.I know I would ned a conversion joint at the rear.
I figure it will lower the rpms down about 1000.Is this worth it?

PS>this is a 61000 mile original rig.
 
Could always just install a GV overdrive unit and not have to change anything except having the rear shaft shortened up a bit.
 
IMO 700r4's are not worth it for replacing a 400. I had one in my 84 blazer and it died a horrible death. Especially to pull one from a junkyard or anywhere else and rebuild it before it goes in.
 
I know these weren't that good in the early versions.But they can be built pretty tough now.The GV units are $3000!I can buy alot of gas with that.How about the 4L80E?
Pretty much all it's used for is me driving on the weekends for errands,camping and towing the Jeepster when finished.I just don't like the engine running that fast down I-70.Pretty much the only way to get anywhere around here.
 
The 4L80E is going to require a $1000.00 stand alone controller on top of whatever it cost you for a trans and t-case.
 
The 700R4 will not hold up no how matter how well you build it. BTDT and I replaced it with a TH400 and 37" tires instead.
 
700's can be built to withstand some serious abuse. When a 700R4 gets built it needs to have all the standard upgrades and then some other upgrades as well then IT WILL survive. I've been beating on my 700R4 hard for the last 6 years since i had my trans guy build it for me and i've yet to have a problem with it.
 
I'm not 100% certain but i don't think a manual valve body will eliminate the need for the electrics still.
 
4X4HIGH said:
700's can be built to withstand some serious abuse. When a 700R4 gets built it needs to have all the standard upgrades and then some other upgrades as well then IT WILL survive. I've been beating on my 700R4 hard for the last 6 years since i had my trans guy build it for me and i've yet to have a problem with it.
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Abuse in a K5 is one thing, put it in a 3/4 ton that weights 1500# more and start towing a load and it won't hold up very long. If you build it up the way your talking about, it will cost more than a stock 4L80E plus controller anyway.
 
kennyw said:
Abuse in a K5 is one thing, put it in a 3/4 ton that weights 1500# more and start towing a load and it won't hold up very long. If you build it up the way your talking about, it will cost more than a stock 4L80E plus controller anyway.
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We could argue the point until we're both blue in the face but the fact remains that the 700R4 got a bad rap from it's early beginnings and some people just want to believe that they aren't good and won't last. My rig weighs 6100 lbs. and i use it, abuse it, tow with it, DD it, and wheel with it.

Oh, i forgot to mention that i paid nothing for my rebuild thanks to a good friend who owns a trans shop but even so he builds 700R4's all day just like mine for under $1000.00 with convertor and all mods and upgrades. Guess if you pay as much as a 4L80E with controller then you need to find a new trans guy. :deal:
 
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