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Old 10-05-2005, 03:21 PM
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700R to 350

I got a 89 chevy van (Work truck 350 motor) that keeps eating 700r trannys. 4 in 8 months to be exact. I got the transmission from a quality rebuilder and he has stood behind the trannys as in replacing the 3/4 clutches each time it has burned them up. He set the TV cable so i know that isnt a issue as well as i run the biggest transmission cooler i could find so i dont think its a overheating problem. I may be hauling more weight than the transmission can handle only the van always seemed to run strong and never acted overloaded. Anyway i am tired of changing out this transmission. I was planing to install a long tail 350 as i am told it is the same length as the 700r so i wouldnt have to change driveshafts. I realize i will loose some on gas mileage and i will have to modify the trans mount but at this point i really dont care. I'm tired of missing work over it.
Does this swap sound possible without alot of driveshaft changes or does anyone have any advice or see anything i may be overlooking in trying to preform this?? Thanks for any help guys

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Old 10-05-2005, 04:31 PM
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Quote:
Originally Posted by JH30906
I got a 89 chevy van (Work truck 350 motor) that keeps eating 700r trannys. 4 in 8 months to be exact. I got the transmission from a quality rebuilder and he has stood behind the trannys as in replacing the 3/4 clutches each time it has burned them up. He set the TV cable so i know that isnt a issue as well as i run the biggest transmission cooler i could find so i dont think its a overheating problem. I may be hauling more weight than the transmission can handle only the van always seemed to run strong and never acted overloaded. Anyway i am tired of changing out this transmission. I was planing to install a long tail 350 as i am told it is the same length as the 700r so i wouldnt have to change driveshafts. I realize i will loose some on gas mileage and i will have to modify the trans mount but at this point i really dont care. I'm tired of missing work over it.
Does this swap sound possible without alot of driveshaft changes or does anyone have any advice or see anything i may be overlooking in trying to preform this?? Thanks for any help guys
I suggest you get another tranny Guy! It does not sound like he knows what he is doing??
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Old 10-05-2005, 04:43 PM
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Originally Posted by ronb
I suggest you get another tranny Guy! It does not sound like he knows what he is doing??
You may be right, however this guy has been in business for about 35 years and has a great reputation. I dont think he's trying to screw me. He's as tired of fixing it for free as i am taking it out and reinstalling it.
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Old 10-05-2005, 04:57 PM
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Do you have the stock carb or throttle body? Has anyone driven it with a pressure gauge to monitor the line rise? Is he rebuilding the excact same transmission every time? Is it only burning the 3/4 clutches? not the band?
what type of frictions?

Sorry for all the questions but i can help much better with these answered
Are you sure you want to give up over drive with gas prices

Brendan
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Old 10-05-2005, 05:10 PM
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700-r4

Do you put the trans into 3rd gear when you are pulling a heavy load? They will not last if you drive in OD with a heavy load. Has the cooler been checked to see if it is flowing enough fluid? Does the torque converter clutch work? No TCC is hard on the trans also.

Rick
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Old 10-05-2005, 05:30 PM
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Its running the stock throttle body. As far as i know he run the pressure check when he adjusted the TV cable. I have installed 2 different transmissions. The 1st coming from Advance auto parts, It lasted about 3 months, the 2nd coming from this guy thats burned up 3rd gear and OD Twice in the last 5 months or so. Both times he showed me what happened. As far as i know its the same transmission.

Yeah i do hate to give up the gas mileage considering gas is $3:49 a gallon here but i am tired of getting broke down. Not only does it cost me the time to tear down and reinstall its also starting to put a strain on my job. I'm sure you guys know what i mean when i say if my vehicle breaks down the family dont eat. NTM if i take it to someone else they will want to charge me another $650 to rebuild the tranny so to me the cheapest option is to do the swap seeing as i already have a LT350.
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Old 10-05-2005, 05:43 PM
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Quote:
Originally Posted by Ricky Rocket
Do you put the trans into 3rd gear when you are pulling a heavy load? They will not last if you drive in OD with a heavy load. Has the cooler been checked to see if it is flowing enough fluid? Does the torque converter clutch work? No TCC is hard on the trans also.

Rick

No i dont pull it down to 3rd, Its never acted like was under a strain or anything. It would always drop right out of OD anytime I pressed down on the throttle trying to accelerate or go uphill. To me it always acted normal, no sliping or anything. In each case I got into the van headed home on the expressway and it suddenly just droped out of gear and refused to go into 3rd and OD. All the lines are new and the cooler is flowing perfectly. I wish i knew
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Old 10-05-2005, 05:50 PM
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You should definatly be sure to get that pressure checked, at idle in drive normal pressure should be 60 psi or somewhere around that, when you brake tourque(hold brake and give gas) it should rise steady to 175 psi approxiamtly, in reverse the pressure should be higher, up to 300 psi
also drive it with the guage hooked up and it should hold the pressure as it gets hot

it is crucial that the 700r4 gets that correct pressure , more than any other transmission, get that checked before you go putting another trans in

Let me know what happens

Brendan
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Old 10-05-2005, 06:41 PM
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Quote:
Originally Posted by JH30906
You may be right, however this guy has been in business for about 35 years and has a great reputation. .
I do not wish to bad mouth anyone! however there are allot of guy`s that have been doing tranny`s just as long and do Not work on the overdrive tranny`s! the 700`s are more complicated and need special care and seal tools!
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Old 10-05-2005, 07:17 PM
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For a repeat of a 3-4 clutch failure , something is being over looked.

Often the steel input shaft where it presses into the aluminum drum will loosen up. IF a builder does not put the drum / shaft into a vise and check for a loose shaft , pressure is lost there.

The stator support area where the sealing rings ride for the input shaft may be a problem.

I am sure the long time builder knows to check boost valves , servo piston bores and related items.

There is a cause , it has not been found yet

the replacement t-350 for the 700 tranny would have have a 9 inch tail housing on it.
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