90 Chevy van transmission

T

TilliamWe

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Well, this isn't a huge deal, but I agreed to buy a 1990 Chevy G20 van yesterday. I was looking up transmission filters and it was giving me a choice of two transmissions it could have. The THM400 or a 700R4. The picture of the trans pan that I remember my 87 G20 van having is for the 700 R4 trans, but the site says my 87 would only get the THM400. So my memory could be totally wrong.
So my question is this: If the 90 van I'm buying has the 700R4, is that really bad? Or is the THM400 bad? The van has 104,000 miles on it, and has done some towing (16' flat trailer) in it's life. And I plan to tow my 1997 Chaparral 2135 (tandem axle galvanized trailer) about 10 times a summer, 14 miles round trip. Is it gonna grenade itself on the first pull up the hill from the river?
Thanks in advance
 
JustJason

JustJason

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Re: 90 Chevy van transmission

THM400 means turbo hydro matic 400 series... and so on with a 700R4.
The difference between the to is a T400 is a 3 speed, no overdrive. A T700 Is a 4 speed, it has overdrive.
The 400 is the best (most heavy duty) 3 speed gm ever made, and the 700 is the best 4 speed they made. hope this helps.
 
dolluper

dolluper

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Re: 90 Chevy van transmission

The 700 is a great transmission .....install a external cooler and when towing use drive {D} not the overdrive
 
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TilliamWe

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Re: 90 Chevy van transmission

dolluper said:
The 700 is a great transmission .....install a external cooler and when towing use drive {D} not the overdrive
Click to expand...


I have the cooler in my garage that I took off the 87 van.

Jason, I thought a 400 should be a 3sp only, (and I knew it to be the best trans ever!) but this link shows that a 90 could have either THM400 or 700R4:

http://www.autozone.com/N,11200543//shopping/partTypeResultSet.htm

Where this link shows the only filter for a 1987 Van as being the one for a THM400:
http://www.autozone.com/R,APP712878...partType,00543/shopping/partProductDetail.htm

And I know for a fact that my 1987 was a 4sp trans with a lockup torque convertor.

But basically, from yours and dollupers responses, I have nothing really to worry about either way.

Thnaks guys!!!
 
SuperNova

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Re: 90 Chevy van transmission

Look at the shift position indicator on the dash. If it has two drive positions then it's a 700. If it only has one then it's a 400. It will also depend on which motor is in it. If it's a diesel or a big block it will probably have the 400. If it's a 5.7 then it's gonna be the 700.
--
Stan
 
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TilliamWe

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Re: 90 Chevy van transmission

Oh this one is definately a 4 speed overdrive. (5.7 engine, no 454 in a G20 van in 90) And my 1987 was definately a 4sp O/D too. So is Autozone's information just incorrect? Cause according to them I had a 4sp O/D THM400 in my 1987.
 
SpinnerBait_Nut

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Re: 90 Chevy van transmission

TilliamWe said:
Oh this one is definately a 4 speed overdrive. (5.7 engine, no 454 in a G20 van in 90) And my 1987 was definately a 4sp O/D too. So is Autozone's information just incorrect? Cause according to them I had a 4sp O/D THM400 in my 1987.
Click to expand...
See how many bolts hold the pan on.
If 13, it is a THM400.
 
SpinnerBait_Nut

SpinnerBait_Nut

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Re: 90 Chevy van transmission

If 16 bolt, it's a 700R4.
If 17 Bolt, it's a 4L80E.
 
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qaztwo

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Re: 90 Chevy van transmission

Also there will be a tv cable on the throttle body if 700r.
 
T

TilliamWe

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Re: 90 Chevy van transmission

From your responses, I see AutoZone has the number of bolts correct. The original window sticker showed that a 3sp auto was standard and mine has the $235 4sp option. It must the 700R4. It ran good on the way home. Gosh, the difference between my old van with a 2.73 rear and this one with the 3.42 is Amazing!
 
SuperNova

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Re: 90 Chevy van transmission

TilliamWe said:
Oh this one is definately a 4 speed overdrive. (5.7 engine, no 454 in a G20 van in 90) And my 1987 was definately a 4sp O/D too. So is Autozone's information just incorrect? Cause according to them I had a 4sp O/D THM400 in my 1987.
Click to expand...
Their info must be inaccurate...there is no such beast as a 4 spd THM 400. They were all 3 spds. When the 400 became a 4spd it became the 4l80e.
 
T

TilliamWe

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Re: 90 Chevy van transmission

MD8 is a THM700 R4. You guys are all correct and AutoZone is just a little messed up at this point. Thanks!
 
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