Transmission question of the day...


Old 11-11-03, 03:05 PM
89blaze's Avatar
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Join Date: Jan 2003
Posts: 140
Question Transmission question of the day...

I have the 3/4 ton, 4x4, 89 Suburban with a 350cid, turbo 400 tranny, and 241C transfer case. I need to go to an overdrive tranny for better performance and milege.
Is the 700R4 and the 4L60 the same thing?
Will the 241C T case work with a 4L60? Same adapter?
Will the measurements be the same on the 4L60 as the Turbo400 as far as the mount and the driveshaft lenghts?
What year of donor trucks (pickup and burban) should be used to get correct transmission and related parts?
Anyone near Seattle want to get rid of such parts?

Correct answers or thoughful ideas will be rewarded with slightly used cases of No Smoke Blinker Fluid produced by Sucka Inc.
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Old 11-11-03, 03:23 PM
Join Date: Apr 2002
Location: Pittsburgh,Pa
Posts: 2,417
The trannys are basically the same beasts,you should inquire at a auto recycler for specific fitment issues.The hollander manual tells them what fits what.My personal opinion is you may increase mileage but not performance.Any time you start swapping adjustments of some kind will be required,some easy some not,also specific to the situation.You will need an aftermarket kit to provide lockup for the converter.
Old 11-12-03, 07:20 AM
carguyinva's Avatar
Join Date: Nov 2003
Location: Shenandoah Valley
Posts: 1,147
in addition to...

...providing for lockup control (which btw will burn the tranny up if you don't have it working) the THM 400 uses manifold pressure to control line pressure in the trans...the 700r4/4l60 use a'd need the correct length cable and a different bracket at the throttle body. I have to agree with Davo...most of the time doing major swaps that appear seemingly uncomplicated turn into lengthy projects. Just to muddy the water a bit...a 4L80 trans is basically a 400 with a two speed unit in the's a much heavier duty unit than the 4L60 and can be retrofitted for use in non-computer controlled applications...this a very expensive proposition, however...core transmissions are big bucks and the harness/controller package required to do this conversion is also expensive. perhaps a newer truck might be the way to go...
Old 11-12-03, 12:57 PM
89blaze's Avatar
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Join Date: Jan 2003
Posts: 140
New truck or newer with what I want = $15000-$45000
Lift kit for new truck = $1000
Tires and wheels for new truck = $2000
Custom roll cage for new truck = $1000
Not to mention the $500 payment you can make for me every month.

My trucks value with lift, tires, and cage all done = $6000
Cost for all parts to do swap = $3000 tops
Weekend = free
Beer and steaks for 2 buddies and I = $100

I am doing the swap. Just wanted to know if anyone had some useful information to help me before I go to the Pull Apart and try to get info out of Jesus and Jose who speak great spanish and 8 words of english.

Now, what trucks did the 4L80 come in and will they work with the 241C T case or do they come with something else?
Old 11-13-03, 04:35 AM
carguyinva's Avatar
Join Date: Nov 2003
Location: Shenandoah Valley
Posts: 1,147

...had no idea of your attachment to that to the bone yard dudes...they can advise all that connectability stuff...good luck and let us know how it turned out...please

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