700r4 To Th400 Bad Idea?

Johnatthebox

Active Member
My 700r4 has been slowly dying, and I'm finally over it, and its time for a new transmission. As usual(especially now with no work) I'm on a minimal budget. 700r4s with any kind of performance build on them are expensive! I found a built th400 that is out of a drag/street car with hardly any miles on it(i think they switched to a 5 speed or something) that I can actually afford .I know I'm probably gonna have to get my driveshaft changed a little, but other than that, I'm thinking this should be an OK swap..... any thoughts?
 
what car are you installing it into, does it or has it ever come from the factory with the th400?
will the trans you buy, come with a shifter and torque converter?
(your parts from a 700r4 are unlikely to work on a th400.)
youll most likely also need a new trans cross member, and trans mount and certainly a drive shaft and yoke,
so the swap won,t be cheap or easy,
personally,
I think Id be looking in salvage yards for a replacement 700r4 trans
many salvage yards sell them with no guarantee, for a couple hundred dollars
and Id look for cars that obviously had been in accidents so you know they were driving when junked, not junked due to a defective transmission.
and Id be a bit sceptical on that th400 deal, you only have the guys word that its in pristine condition, he may have pulled it when it broke,
and is simply trying to get some cash return on the core,
 
Why not build the 700R4 yourself, it will certainly be a learning experience but fun ! I built my
first ever 200-R4 automatic a few years ago and it came out good. You just have to be well organized,
label everything and methodical about the process.

This time of the year going into fall, you will have all winter for the project unless it's your daily
driver. Oops, I just checked and you live in California, maybe a short winter.

What is your budget ???
 
I was prepared for the driveshaft, but the crossmsmber and mount too?!? I wasn't aware of that. Its for a 73 elcamino. I have a junkyard 700r4 already, but I dont know any history on it, except that its completely stock. I'm confident in the th400 being what its supposed to be, but an expensive swap would be just as difficult as an expensive replacement 700r4.
This is why this forum is golden for me. I have no one to bounce these ideas off of here.
Well, back to the drawing board I guess...frustrating....
I'm gonna look into affordably beefing up the junkyard 700r4 I guess..... if possible
 
Last edited by a moderator:
Im sure the trans could be rebuilt and, if you go that route..
youll learn valuable skills and knowledge doing the rebuild

browse through this thread on rebuilding a 2004r

it might give you some ideas

http://garage.grumpysperformance.co...ransmission-holding-bracket.13252/#post-77777


http://garage.grumpysperformance.com/index.php?threads/tbucket-200-4r-transmission-project.7230/

yeah getting in over your head in projects is SCARRY:rolleyes:
at first but you'll rarely learn new skills if you don,t try new things:D

https://www.monstertransmission.com...MI9ezXh_OH7AIVx8DACh3uZwMGEAQYASABEgK8oPD_BwE









 
Last edited:
Yeah...its not that I'm scared to try new things as much as its that I'm really bad at making decisions. The more I overthink a problem, the more either solution seems both plausible and impossible at the same time. Its also because either way this is gonna be a big spend for me. I've got one shot to do this, so I am hesitant to pull the trigger and commit to a solution. BUT, my slipping 700r4 in my car is forcing me to decide. Also, it always makes projects seem bigger when you're trying to do them on the cheap....
These are my thoughts on either option-
Th400 -
It wouldn't be hard to come up with a crossmember and mount because that's what came in the car originally. I would have to get a new driveshaft, converter, and im not sure about the shifter (b&m megashifter)
With the deal on the tyranny I could prolly get it all done for $1000

New 700r4-- prolly $1600 +shipping
Easiest route, but not really affordable right now

Build 700r4 myself--
Looks like performance rebuild kits are around $500 and im not sure about the special tools I would need.
With everything I'd need lets say $800 prolly less.
Definitely the cheaper route but id be counting on the rebuild to go well, cause there's no bail out if it doesn't.

I'm going to do some internetting and see how others have done at building their first 700r4, and then decide......
 
post lots of pictures and ask lots of questions, never assume anything,
but get a couple of detailed transmission rebuild manuals ,
and watch a few instructional videos before you start,
and personally Id look for an experienced mentor, if you can find one


ID START gathering instructional info HERE
https://www.monstertransmission.com...VBI9bCh2rkQG8EAQYAyABEgJiMPD_BwE#.X3H2MmhKi9I





http://garage.grumpysperformance.co...t-info-and-related-700r4-info.857/#post-70096



https://www.monstertransmission.com...VBI9bCh2rkQG8EAQYAiABEgLu4vD_BwE#.X3H2fGhKi9I

https://www.amazon.com/1987-1993-Tr...77Y1RX233FE&psc=1&refRID=02NA02K4V77Y1RX233FE

https://www.amazon.com/ATSG-700-R4-...E1HE68HDYPH&psc=1&refRID=4R99SBRB7E1HE68HDYPH
 
Last edited:
Definitely going to set up a TV in the garage and do it alongside a video tutorial.
As for a mentor, pppffbbbt!! I wish...
I'd be thrilled just to meet someone else who likes cars. I live in Vallejo CA. about 5 minutes from Sears point (Infinion) Dragstrip and the only Gearheads I run into are kids in fast import tuners, or LS transplant drift cars. Considering my location, every weekend there should be a conga-line of pro-street cars parading up and down the block, and street racing till Monday. Or at least a cruise night or something. Nope.

I blame the internet(don't know why it just seems like it should be blamed).

I'll keep you posted on my progress. Thanks for the references
 


yes aftermarket parts ARE AVAILABLE FOR MANY G.M. TRANSMISSIONS
can be installed ANY TRANSMISSION THE PARTS ARE AVAILABLE FOR TO INCREASE ITS STRENGTH/
DURABILITY BUT THERE ARE LIMITS AND THE LARGER TRANSMISSIONS LIKE THE th400 AND 4L8OE
DO HAVE STRENGTH ADVANTAGES

https://www.monstertransmission.com/700R4_c_3942.html


transtrength.png

length.png
 
I think because I have the second 700r4 already, so I can still limp around town while I'm building it, and also the whole crossmember driveshaft problem, it makes the most sense to stick with 700r4. Im barely ever on the freeway so I never even take advantage of the overdrive. Its just what I have. Personally I'd rather have a 4 speed. But for now 700r4 it is......
Any recommendations for which rebuild kit to get? What company to go with? . I know about Monster, and someone on here mentioned probuilt automatics
 
What HP/TQ do you need from this 700R4? Just your best guess will do, but please be on the
conservative side ???

AGAIN, what's your budget ??????

I can't speak to the 700R4 directly, but you need a smaller shop that you can call and talk to directly
for advice and order parts from, . For me and my 200-R4 that was CK Performance or Turbo Buick
Performance, I choose CK Performance. I would think that CKP could do the same for you and your
700R4, since you are not on the bleeding edge just a performance street trans. Call and ask Chris/
Dave Husek what you need and then place the order, call them when you need advice or have questions.

Now both are experts on the 2004R, but could probably guide you thru the 700R4, but that's why I
know about them, you need to find your expert.

https://gearstar.com/overview-700r4-transmission/

http://garage.grumpysperformance.com/index.php?threads/tbucket-200-4r-transmission-project.7230/
.
 
keep in mind when I post info and links, in any thread,
it may be related to, but not specifically meant for your build or project,, I simply try to
post info that someone reading this thread months or years later might use.

Id suggest you look over all the kits and parts lists, watch the videos and purchase a few rebuild manuals,
and perhaps visit a few local transmission rebuild shops and ask what kits they suggest
tell them you want to learn how to rebuild a 700r4 and would like some info,
tips and suggestions on how to do it and where you can learn to do so,
there may even be classes someplace that you can register for,
if you look at this as a skill you need rather than an expensive P.I.T.A,
that needs to be dealt with,
it may prove very helpful in the long term


https://www.bonanza.com/listings/70...MI492GwPeM7AIVMvC1Ch0VPwucEAQYBSABEgKVKPD_BwE


https://www.ebay.com/itm/700R4-1987...3-Shift-Kit-HD-Torque-Converter-/382924065419


https://www.ebay.com/i/173792584586...MIy--z-_WM7AIVAtvACh2UAwB5EAQYAyABEgLcEPD_BwE
 
Sound advice for sure.
I've watched some of the "rebulid your 700r4" videos available on the internet and I was surprised at how thorough they actually were. I think i can do this. I need to find that specialty tool kit for the 700r4 rebuild and purchase it.
This whole car has been a big learning experience. First time with EFI, first time with ECU, 700r4, etc...
I do miss tuning with a screwdriver and a vacuum guage...lol
But.....things change.....
 
What HP/TQ do you need from this 700R4? Just your best guess will do, but please be on the
conservative side ???

AGAIN, what's your budget ??????

I can't speak to the 700R4 directly, but you need a smaller shop that you can call and talk to directly
for advice and order parts from, . For me and my 200-R4 that was CK Performance or Turbo Buick
Performance, I choose CK Performance. I would think that CKP could do the same for you and your
700R4, since you are not on the bleeding edge just a performance street trans. Call and ask Chris/
Dave Husek what you need and then place the order, call them when you need advice or have questions.

Now both are experts on the 2004R, but could probably guide you thru the 700R4, but that's why I
know about them, you need to find your expert.

https://gearstar.com/overview-700r4-transmission/

http://garage.grumpysperformance.com/index.php?threads/tbucket-200-4r-transmission-project.7230/
.
On paper my engine combo is good for 400hp, so let's call it 375. My budget to get this all done is around 1000 bucks
 
I can recommend this guy, he is a one man shop and is easy to get a hold of for a phone conversation.
@JohnHancock used him for his parts and called him 2-3 times, I was impressed with his service. Handling
400 HP in a cruiser should not be very hard, you are not racing so you are not putting a big load on
it very often. But I suspect there will be a few parts that will need upgrading, so ask him if you call and
see what he recommends. Also do your research, don't depend on just one opinion.

His most complete kit is $255.
http://transmissionbench.com/700R4parts.html

This is the guy you would be dealing with. I like his slower approach to his videos, gives you time to focus in
on a part in question. The 4L60E is just the electronic version of the 700-R4. He has 19 videos on the 4L60E.

.
 
Last edited:
Back
Top