THM700R4, 4L60 & 4l60E, V6's & V8's

[robertbruce]

My THM700R-4 is cactus, reverse engages but slips crazy...

I am trying to get my head around which tranny to buy, how to physically identify it and the differances in the range... i want to avoid V6 T7's, however if i have the v6 varient fitted i would not know...

I would be better-off to repair what i have but im thinking to throw another box in it to keep mobile...perhaps even a upgrade to a 4L60E

My THM700R-4 is mounted to a 350Chev
On the passenger side of the casing is 8663549
There is a big "6" stamped up to the left of it...
I am yet to find the full tag...

This THM700R-4 may be funky (shaft-length) on the output end being it goes to a F Series 350 transfer case...
The output shaft casing is stamped as a T7.

Im hoping all the the drive shafts are standard so i can look at putting a 4L60 or 4L60E in.
Does anyone know if there is there much stuffing around apart from speed-sensor, speedo, cpu, gear-selecter etc... to put a 4L60E in it?
I have a Hurst shifter

Im not sure how many splines are on my input shaft or how to find out - box is still in?
Im not sure how to tell the differance between a V6 or V8 THM700r4 or a 4L60 or 4L60E?

can anyone help with these questions

[OzBinder]

Im no expert and can only pass on info i have or been given.

I have a 4L60E and from what i have been told the boxes you mention are all basically the same. Except the 4L60E which is controlled by the computer in my case the standard commodore unit (one ecu controls engine and box). As far as i'm aware the V6 and V8 boxes are the same.

As you said your better off fixing what you have.

In my case (box came out of 2WD commodore) to adapt the auto to the transfer you have to remove the standard ouput shaft and put one in to suit the transfer and adaptor, so its not just a simple replace the box with one like it, unless you pull it apart to get the output shaft from it to put in the new one.

Hope that helps you and not confuses you.

[DamTriton]

Addit to above comments: Output shaft replacement is best left to a transmission specialist as the output shaft is one of the first things to go into the case during assembly. Everything else gets piled on top up to the input shaft and torque converter. Not a job to do without the knowledge and familiarity of what you are doing.

Generally about $300-400 to have the shaft replaced

[robertbruce]

thanks for your replys - i reckon i wont know what the box fully till i get it out





some homework - google the link descriptons, there is too many for me to convert

the out put shaft on the t-400 is larger than the 700 tranny
Did you have any trouble inserting the converter into the tranny?There were two different splines used.......a 27 and a 30 spline version was used in production.Early 700R4's from 1982 to 1984 i think used the 27 spline converter,while from 1985 onward the 30 spline was used.I think if you tried to install a 27 splined converter upon a 30 spline input shaft or vise-versa,it would'nt fit anyway.

he means the kick down cable. when you select your engine make sure you get the trans and computer so it all matches. some vr and all vs on commodores have fully electronic controlled autos and you need the right computer to run them. pre vr ran the kick down cable and manual and auto computers are the same


The 700r4 still works/shifts from fluid pressure. The fully computer shifted transmissions are the 1993 and up 4L60E and 4L80E's

[OzBinder]

Thats totally different to what i was thinking and to most conversions.

You have a standard gearbox then a very short driveshaft to the transfer case. Mine and most of the ones i have seen has the transfer bolted to the back of the gearbox which is why the output shaft needs to be changed.

In your case it would just be a matter of finding out what box it is, get another one to put in there for now and repair/rebuild your original. Or better yet get one that is in good nick thats had a rebuild and put that in.

If you can get it to a good auto gearbox specialist they should be able to tell you what it is. Or try to get the info from the previous owner (if possible).

[robertbruce]

manys for that OB, your conclusions are exactly what i had come to... get it out, get another one in, get the first one apart and get it fixed...

utube "how to fix your thm700r4 in your driveway" has been very good help

[offroader-rama]

first i saw your pics on the other thread awsome rig
now i have a v6 auto in a mazda e2000 try truck its a 4l60e but have had the same issue it has dropped reverse a few times when it does i flush it out with about 10 ltrs of fluid and it usualy comes good. i did this 3 times in 2 yrs the third time it was well and truly cooked.
i had a new box built with all the goodies stage 3 shift kit bigger stall lock etc and run a huge front mount trans cooler.
this shifts heaps better and drive way better if you like to "drive your car", but as another hick up as happen with the standed box when i have the ute loaded up with a heavy load and do a decent trip it drops 1-2 gear for a day or so then comes good.
its my third box in 6 yrs this one has been the best by far but honestly the next time i wouldnt touch a holden/chev 4sp auto if it has to pull any wieght which you and i both need to do. ( mine is only around 1200kg empty but takes enother 1800kg loaded total 3000kg)
unless its my advice take it or leave it, is either spend a little more and buy a 4L80E or go back to a 3pd turbo400 other wise you "will" destroy box after box.
you will find people that will tell you, your box is good for 600-700 hp but in a 1500kg car not a 2500+ kg brick.
what revs are you doing at 100klm you may not need a 4sp etc do some research on your gearing before you do much more as its already geared up with your 33s so if your diff ratios are any were up to say 4.1 you could happerly get away with the cheaper stronger 3 sp.
ps. do a search what all your chev trucks use only on the show ponys will you find a t700 there all aither t400 or 4L80E

there is enother option and that is a nissan 4sp auto much stonger would need to either manulise box or run a computer etc if you want to investigate that path PM me i maybe able to help

from my findings my 2 cents IMHO

[robertbruce]

many thanks for your comment OR.... ive just finished fine tuning it...it's got a stage2 transgo with o/size valves, servo etc, a superior shaft etc

inspite of all the goodies i completely agree about the weight vs HP for this box, but im not sure if anything short of a true truck drivetrain would suit the weight issue... the nissan or possible a 4L85e and certainly gear ratios to suit the wheels are worth a look at...

the wheels are the whole problem i think....i would prefer then much skinner and taller, maybe a t350 would suit better then.... problem is my wheels are engineered to suit the truck and i hazard to stray from insurance issue...

all-in-all, i've thought if i could be disiciplined or make a hobby of rebuilding one, then i could probably bear it - what i couldnt bear is burning one out an low tide.... 3+ tonne is hard to move off the beach in my books...

[offroader-rama]

The T400 is way stronger than the T350 and the 4L85E is a T400 with a over drive, there the truck boxes you want or the nissan is a very good box and comes with a transfer etc but if your useing f100 transfer your front diff punkin must be on the left side and nissan is on the right you could locate a right hand punkin dana diff easy enough from a jeep or chev or use nissan diffs but then your starting all over again.
so your only options long term, are see what ratio your diffs are and if a 3 sp auto would work then the T400 is a strong low cost better option for around $1800 ( IMHO ) or the 4 sp 4L85E but be prepared to spend better part of $5000 by the time its fitted and changing gears properly.
enother option i just thought of and you have room for it is go a T400 and put an after market overdrive unit between the T400 and the transfer it would still be heaps cheaper and the overdrive would be turned on and of with either a switch so it could be on at all time if wanted or set it up to work your speedo and transpresure so as it only turns on over a certain speed when you box isnt working hard ie. coasting at 100ks

food for thought