Randy82WS7

hey all,

i just got another third gen f body today,,
and i have a Q or two..

i heard a little rumor that the stock 82 83 thm200 shaft will work for the short tail th400 2wd trannies in the third gens?
is this true ?

anyone who has put a th400 in one of these cars: can you tell me what you did for a driveshaft ?


background and info:

the car in question(85 Z28) is currently is 355 and th350 with the 2wd truck 9" tail length(700R4 length), and we just yanked that drivetrain combo out tonight, a couple hours ago.

this car was originally a 2.8L/manual trans way back in the day years ago,

i plan on putting in another 350 engine, but with the 87 pickup th400 tranny this time,

i do have a 700R4 length th350 i could put in, but i dont have a gas engine torque converter for it, and its 80-up lockup style, so finding a gas engine th350C converter is like impossible for me to find around here, the th350c i took out of an 81 c-10 pickup with 350 oldsmobile diesel in front of it, it would bolt right into the z28, but..... cant find the dang torque converter i would need to run the gas engine in front of it,,,,,,

so its back to the th400..

but the driveshaft length,,


thanks for anything on this.

EvilCartman

iTrader: (1)

Yep, I'm using my stock 82 driveshaft with a TH400 slip yoke on the end. The length was fine with a short tail TH400. Why do you want to replace the TH350 that you just took out?

Randy82WS7

hi thanks, so its short tail th350 and th200c length ?

neat, but its not all that good since i dont have a 200 shaft laying around so hmm ill have to buy one off someone, or have a longer shaft laying around here cut down(probably the latter)

and im like 75% sure i have a 400 slip yoke shaft laying around somewhere here, hmm ill have to dig through them all and see,

and then get the B and M tail shaft mount TA brackets,

i think on the th400 swap you just needing the stock outer clamp part of the mounting brackets, and not the bigger part that bolts to the tailshaft directly ? no ?

the 400 trans has to go into this car because i dont own the drivetrain(350/ th350) that we all pulled out of it last night

i am trading my 87 pickup rolling body for the rolling camaro

thanks

Randy82WS7

oh wow.....

well i got the engine and trans out of the 87 c-10 today and well the verdict is back,,

the th400 in it is an oddball,

its not like the 3/4 ton and 1 ton version of the 80's th400 trannies

this one is a slip style output shaft and overall the trans is about 35" long......

wow...


is 35" normal length of the long th400 trannies ?

like the 70s and older ones ?



usually the later truck th400 were short tail and had bolted on style out put shaft yoke,


not this one

it yet it still has two piece driveline, but its only 70" from axle to end of tranny(longbed 131.5" wheelbase)






thanks fpr anything

EvilCartman

iTrader: (1)

I'm not sure on the TH350 info but the 200c and short tail TH400 are within a half inch in length of each other. Used to know the numbers off the top of my head but not anymore hehe. You can always put the TH400 in and do some measuring to make up a new driveshaft, they're not all that expensive to have done.

AlkyIROC

It's rare to find a slip yoke TH400 in any truck. Make sure it's really a TH400. Will the slip yoke from a TH350/700R4 fit? If the shaft is larger then it's really a TH400 and not some variation of it. TH375 etc.

Randy82WS7

yeh the 200c vs. the short 400 sounds right

they would be VERy close to same length overall, not exactly, but close enoguh to use the same D shaft other than the yoke since 400 are oddball 32 spline

hehe


yeah i can just have this haft in this 82 cut down,

no biggie really, but what about my crossmember location ?

the 400 tans mount are waaaay back farther than the other models

im gonna have to drill holes in the subrame, eh ?

whos done this one!

help! /me falls on floor again


lol


thanks

Randy82WS7

yeh this one is an oddball cuz its an 87 305 TBI with the 400 trans(IL or TX shaped pan and the orange wire kickdown and no cable)

it is a "th400" no doubt about it, but...

it is 35" overall length.. give or take around an 1/8" maybe though,

and you know what,,,, i DO think the output shaft just might be a 27 spline, it does look smaller than a 400 one, i kinda was looking at that as i was yaning the driveshaft out of the ed of the trans just before pulling the 305 and 400 out,

hmmmm...


was the 375 around in 87 though ??

i thought that was a 70s era trans ?

what ?


oh and what was the length of the 375 ?
(400 case and 350 output- whichever 375 that is)
or was there more than one length of the 375 ?

GM did something real odd with these th400 c-10s in the 80s

this is the first 80s c-10i have ever seen with 400 trans in it and its not the typical short tail 400 with the bolted on yoke like you always see,

nope.

very wild..

100% of all 80's c-10 trucks i have ever seen/came across have had either th350 longtail, or the 700r4 in them- if were not 3 or 4 speed manual(i had a saginaw three on the column/tree manual trans '84 c-10 not too long ago, so those 3 on the tree shifts were still aorund in the mid 80s even lol)


either way id like ot cut the 82 Z28 driveshaft down and put this trans in the car,
after i figure out how to move the crossmember back that far ?? wow..
:O

and which B & M torque arm brackets kit to get ?

this "th400" doesnt have the th350/700r4 tail shaft housing bolt pattern design

its not that common 4 bolts pattern like you always see,
no.. nothing even close to that,..

and i have forgotten what the normal th40 tailshaft housing bolt pattern was, or even if they were also 4 bolt, or more than that.

lol....

this "th400" is 5 or 6 bolts tailshaft housing bolt pattern


thanks for further on this

AlkyIROC

My guess would be that the truck was spec'd with a towing package or someone found an old TH375 and put it in to the truck. Nice thing about the trucks, many parts could be easily swapped around to still make it look like a fcatory installation.

My 91 454SScame from the factory with a 4L80E. The 91-93 454SS trucks were the only 1/2 tons to get this tranny but anyone with enough time and money could take a 350SS and make it into a 454SS by changing the entire powertrain and driveline. Everything could be exact except for the N engine code in the VIN.

Looking for codes on the truck could tell what was originally in it. Most of the time I don't really care. It's the component I'm after, not what it came in.

Randy82WS7

3 speed auto is original to RPO label

it wasnt hack job truck, it was a pastor owned truck he didnt have anything even close to this kind of work done to it he gave me all the receipts for it and also the dealer ship papers from when it was bought brand new

the hood had never been off the truck yet or nothing, if you saw it you would agree, its a non molested all factory original truck, nt screwed with

i molested this truck lol


the trans is 35" overall, it has 400 pan, it has 400 electric orange wire kickdown
that is 4" longer than the 9" tail th350 trannies and the 700r4 trannies

this is what threw me off initially.

i was like " what the hell?!"

crossmember was stock original, and everything else too, also including stock two piece driveshaft, and all,
70" from end of tranny tail back to the u joint cap seats in the axle pinion yoke
longbed 131.5" wheelbase pickup 2wd

these trucks(73-87) that got the longtail 350 or the 700r4
were 74" in this dimension and were one piece driveshaft, so this 400 looking trans is right on 35" long overall


everything is right, 80s style stock factory, the trans is definitely not an old 70s casting, for sure, all you have to do is jut glance at it real quick and oyu can tell immediately its an 80s casting, for sure hehe


it has sway bar and such so maybe it did come with a package

who knows,

ill have ot get info off the side tag and let ya see, hell it may even say what modle it is right on there lol!


duh for me,.

also will look for stamping code in the case and it says HD on the bellhousing i know, and another couple digits too,


thanks

Randy82WS7

ok i found out some info by researching

i found out that the 375B is th350 pan, and last used in 76

so this oddball 87 tranny is not one of those

here is tag info off this tranny

247 LJ A

HYDRAMATIC

87 LJA 8994


87= year

the truck was bone dead stock all original

everything matches


but what the tranny is, who knows,,

its a 400 externally in every way so far

chevy 6 bolt bellhousing pattern without BOP pattern

and has 6 bolt tailshaft housing bolt pattern



what do you think now ?

i guess ill have to see if chevy dealer can decode it for me ?


it looks like i can use the TH400 third gen F body torque arm mounting brackets kit
after i figure out how to move the crossmember back the extra 3 or 4" that will be needed, and have the driveshaft chopped down 4"

AlkyIROC

I was under the impression that all TH400's were long and required those modifications to install them in place of a TH350 or 700R4. At least all the ones I've seen are like that.

Randy82WS7

nope all the 80s C-20 and c-30 400 trannies are the shorties with the big bolted on output shaft yoke

look under one and youll see what im talking about

also the suburbans

not 4 wheel drive*


only 80 or 81 and up*

20-30 series

these 400s were still the usual 32 spline but had a threaded hole in the outputshaft to bolt the big yoke on it,
you can remove the yoke and use a normal car(or c-10 apparently) slip style output yoke on it- its the same 32 spline shaft other than the bolt hole or lack of one in some cases, but i dont recall ever seeing a th400 shaft without the hole in the end of it



before this 87 c-10 i had never heard of nor seen a 35" long th400 tranny in a c-10- let alone a 2wd one, and plus 27 spline output

although im sure some 2wd c-10s probably got a th400, although uncommon as ive had and been under billions and never found a th400 yet, not under a c-10
the 70s ones are probably longtail slip output also i bet

evilcartman sounds like he knows what i am talking about, as he has a shorty tail 2wd th400
but they also put the shorty 400s in the cars like the 79 or so and up caddies, etc ive snagged a few before such as out of a 77 electra and a 79 caddy limousine, etc, but they didnt bolt the output yoke on, but the threeaded hole is in the end of the output shaft for one(for 80s 20-30 series truck use)


th400 are pretty complicated lol

basically i have found an 87 th400 with slio put instead of bolt out, and its a long tail

just plain oddball imho, but factory original

learn something new everyday eh ?

some ppl think all 400s are short and others think they are long, and well the truth is that theres two lengths of the 2wd th400s,

and some ppl have no clue about the th350 tranny lengths, on them there was 6" tail and 9" tail and then the long 12" tail

3" was the 4x4 one, no tailshaft housing at all,

crazy huh ?

its all true.

4 different th350 lengths altogether

good thing theres only one 2004r and only two 700r4 lengths(corvette 700 are a little over an inch shorter than all other 700's)


what do you think now ? lol

ive learned a little in the last couple days now
and maybe some on here have learned some things too
thats what this is all about

Randy82WS7

oh wow

i just found this:

http://en.wikipedia.org/wiki/Turbo-H..._after_1990.29

do some scrolling

good reading

i forgot about the little mid to late '70's thm200 and thm200C(also is same length and spline as the 6" tail th350 and th350C and thm250C and thm2004r trannies)


and, OMG... check this one out

http://chevcarclubvic.org.au/technic...tification.htm

375 is another tranny different than the 375B

and then theres the 3L80HD and the THM475HD

i think that this one i have is one of these latter ones
since it has HD cast on it in big letters, and its its a THM(the pan is scripted turbo hydramatic across it,

i need to find pics
and i need to look under the tailhousing for a cast 375THM on it

quotes from page:

"THM350 - Medium duty 3 speed trans used from 1969 to 1989, Used in Buick, Olds, Pontiac and Chevrolet cars and Chevy & GMC light trucks until 1987. Generally used in straight and V6 and small block engines. Generally able to handle up to 400 foot pounds of torque.

THM375B - This trans is identical to the THM350, but is considered a heavier duty transmission.

THM375 - This transmission is a derivative of the THM400 sharing the external appearance of the 400. It'll be marked 375-THM on the bottom of the tailshaft housing. It's a light duty version of the THM400, has ABSOLUTELY NO RELATION to the THM375B, and was found in 1972 to 1976 full-size cars. The Turbo 375 was modified to accept the Turbo 350 driveshaft yoke.

3L80 - The 3L80 is a renamed THM400, used in the early 1990's. The 3L80HD would be the THM475 (heavy duty unit) "



this is getitng complicated


GM made a bazillion trannies

tons!

a total mess!

lol

Randy82WS7

called dealership jut now with the tag info and yep it is the 3L80HD and according to everythig ive sene online it a re-named THM475


finally know what the heck this thing is

th400 TQ arm brackets should work fine with putting this thing in the 82 Z


thanks

Randy82WS7

got pics of the 3L80HD finally, this is from last week when i yanked the drivetrain out


http://www.picturetrail.com/gallery/...9104&members=1

Night rider327

iTrader: (13)

Thats just a common long shaft th-400

Seen them many times in trucks. In trucks the th-350 and 400 was long tail shaft transmissions.

In the 3/4 ton and up trucks/vans the th-400 has a bolt on yoke. In all others the trans is slip yoke.

The lenghts on the th-400s are

short shaft 28-1/4"
long shaft 34"

Theres 1 big prob with putting that trans in a third gen..

On the th-350's the face to mount is the same for both the long and short shaft trans, just longer tailshafts but

On the th-400 the face to mount is 26-3/4" for short shaft and 28" for long shaft.

The B&M kit won't work on a th-400.. You have to change crossmembers to put a th-400 in. The frame rails don't have enough to drill so you have to have the aftermarket off set cross member.. The hurst swap kit for $125 comes with the new crossmember and torque arm bracket.

Now the prob with the long shaft th-400.. The crossmember will have to have a steel tab set back 1.25" for the mount to match up.

Now just some info for you..
For driveshafts

A th-400 short shaft trans can use a 200C 3 speed shaft
A th-350 long shaft trans can by swapped in easy if you use a 700r4 driveshaft.

Randy82WS7

you have everything right except the part about this one being a th400

its not a th400

its a 3L80HD which is a thm475 in which i confirmed with the tag info at the local chevy dealer

it is a longer than a long 400
it is 34 and 5/8" overall length

and has the 27 spine output shaft


have you ever had or seen a 475 trans?

ive had a billion cars and trucks with a 400 trans,
both lengths,
but they all had an actual 400 trans= 32 spline

this is the first time ive come across a 475

pretty different

i already knew everything that oyuve said in your reply,



thanks for tryin