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iTrader: (5)

I want to do a TH400 Conversion to my 94 LT1 and i dont even know where to start. Also, i need to do a rear end swap weather its a 12 bolt or 9inch which one is better and which is cheaper to put it. what is intailed with putting these mods in like control arm, sway bar etc........ any help would be appericated. Also, does any TH400 work or do you need an exact kind ?

lt197formula

iTrader: (6)

I'm not sure about the TH400, hopefully someone else drops in to cover that. As for a rear end it depends what your plans for the car are, street, track or both. Since you are an auto I would say 12 bolt beause autos don't put as much stress on the rear ends as manuals do. The pricing is quite close for the two if I remember correctly with the 12 bolt allowing you to keep ABS and the 9 inch does not. The 9 inch is slightly heavier and stronger but there are plenty of fast cars running 12 bolts so I wouldn't be worried unless this is an all out track car. You will need a torque arm, torque arm relocation kit, and I suggest lower control arm relocation brackets and lower control arms. A sway bar would be good but I'm still running a stock one so I don't know much on that. Hope this helps.

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iTrader: (5)

it helps for the most part. what about putting stronger axles and a upgraded cover on my 10 bolt with that help. The is made to race on the track but drives around town too. It does go mid 11s on my 10 bolt and a small converter right now. i really dont want to spend 2,400 on a rearend and a then all the re-location brackets etc..... plus install your looking at a easy 3,500 conversion, that i really do not want to spend. Any way to help the 10 bolt ?

GIZMO

iTrader: (8)

You would be much better off with a TH-350 over a TH-400 unless you are going to make huge HP. Otherwise you are wasting HP. I would also run a 12-bolt over a 9 inch for the same reason. A 2.75 gear set in the TH-350 would be a good upgrade. You can also buy cheap kits to adapt the stock torque arm to a TH-350 (I used to cut low 1.4 sixty foot times with one).

Good Luck,

Daren

97ssmokem

I think BMR makes a kit now to go from a 4L60E in an LT1 car to a TH400. They didn't when I did mine I had to find ways to make it work. It's a great tranny but like said above you loose more hp then with a th350.

slick1851

THs will bolt up to our blocks, and you need a different tail shaft, and maybe a trans brace..theres a few other lil things but a easy swap..

I suggest leaving your rear end alone, not alot of people are breaking rear ends on the street....

But since your auto just go with a 12bolt....unless you making HUGE power...

Puck

iTrader: (17)

The LPW brace kit with support cover and stronger studs is plenty for most street driven auto lt1s, maybe aftermarket axles if you want extra insurance. It addresses the main problem of the 10bolt, which is where the axle tubes walk under hard acceleration, which takes the gears out of alignment allowing them to shear and shred themselves up. As long as the gears stay perfectly meshed they can hold up to a lot more abuse...wheel hop and axle tube movement can bring them out of alignment.

Unless you are making huge power from an auto it should hold up fine. I know of at least one person who dead hooks with full slicks from 4500rpm in a 6speed with it and it has held up for quite some time *knock on wood*. An auto wouldnt put nearly the same amount of stress.

OutlawZ

iTrader: (4)

Rearend depends on plans..... I have personally 3 friends that have shelled multiple "built" 12 bolts.... I've never seen a 9" break (which is why one sits under my car).... You have an auto but you're talking about TH400'ing it so maybe a t brake is in your future which i'd lean toward the 9".... why worry about it...

The stuff you'll need for a Th400 swap is like this...

I believe you need the 400 with the 9" tailshaft first off..... Here's a list of stuff you'll need to make it happen.

Converter
Flexplate
Transmission cooler (external)
Braided steel lines from tranny to cooler (Must be lines for use with tranny fluid)
New Torque Arm that does not connect to tailshaft of tranny (Spohn and BMR make one)
Shifter for tranny
Crossmember (T56 x-member will work or you can order a tubular one from BMR)
custom length driveshaft (you will need to measure once you install tranny)

that's about it.... other odds and ends might be the VSS sensor you'll need to get it to mate up with your stock computer so you're speedo will work etc....

You can do a TH350 if you want depending on what power levels you plan on but then again you don't know what kind of beast your car will be in a few years so why skimp....

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iTrader: (5)

I appericate the help guys espically outlaw it helps out alot.
here is what im going to do for the rear end.
im sticking with my 10 bolt however im changing from the stock carrier to a auburn one, Then im putting different spider gears into it, upgraded moser axles w/ longer studs and putting on a aluminum gridle for heat reason.

As, for the trans i just recently put on a trans cooler but it has been leaking trans fluid on thus the reasoning for the bad shifting issues but im also upgrading from my 2400 stall to a 3800. Now does anyone know why 3rd and 4th gear blowout in the 4L60E and is there any perminant fix ?

96capricemgr

iTrader: (1)

The 3-4 clutch packs are a weak point, the answer is a competent builder. I mean a truely competent builder not billybob down the road who says he can do it. I mean ProBuilt Automatics, FLT, CPT, or the other CPT, Rossler, there are more but these just came to mind, they are not your run of the mill shops. These are guys who have 4L60Es lasting in serious power applications, I know several of them have customers running 9s on 4L60Es, Rossler has a customer doing that in a 4400lbs Impala. I see little reason to go to a three speed unless an all out race car. When I ran my 11.9s it was on a three year old ProBuilt I had asked him to build for a 13 second car, obviously my plans changed along the way. Tranny is still doing fine, changed fluids and filters redrilled one hole in the seperator plate when I added the extra power that is all the attention it has gotten or needed.

Last time I was at the track I helped push a friend's Camaro onto a trailer, fragged the spiders in the Auburn Pro on street tires with a 6 speed, best ET ever out of that car was 12.8 on slicks with the old automatic tranny so it is not making huge power or anything. He had a cast diff. cover on it too with the preload studs. Was not a hard launch attempt and the track was poorly prepped, don't think it lasted long enough to shake the tires.

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iTrader: (5)

thanks for the help. I have had the trans redone before but this time i went with a probuilt trans from DRC transmission. Most guys in IL knows who that is. I also put on a trans cooler this time and the trans has been holding up fine. However, i have notice the lines in the trans cooler have been leaking alittle bit. could that be a issue with shifting ?

96capricemgr

iTrader: (1)

If in IL I would go with FLT.

When I said "ProBuilt Automatics" that is the name of a shop out in CA and the guy who did my tranny.
Before this I had one done at one of the big reputable shops in Green Bay, blew it up in just over a year making much less power than I told them it would have to take.

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iTrader: (5)

FLT ?
never heard of them....
any information of them.

96capricemgr

iTrader: (1)

http://www.finishlinetrans.com/

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iTrader: (5)

seems like some serious **** in those trans. thanks for the link

OutlawZ

iTrader: (4)

yeah like caprice said don't think that a flimsy cover and different spider gears will solve your problem with your 10 bolt since you seem like you want to maybe stick with the 4l60.... It's just not a big enough strong enough unit to deal with alot of power when combined with traction.... on street tires it'll last all day but when you get tired of 2.3 second 60' times you're going to want some good tires..... and then welcome to blown rearend land...

Believe me I shelled 5 of them at 500 bucks a pop to fix em before I learned.... with the cost I had in repairs I could have done a 9" to begin with. I bought my 9" when my wife was my girlfriend in like 1997. same 9" sits under my car to this day without so much as a whimper...

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iTrader: (5)

well trust me im already in rearend braking land lol. Im pulling 1.4 to 1.5 60FT im running a 26 x 11.5 x 16 E/T Street and pulling mid 11s with a small 2400 stall and a 3:73 rearend stock housing. This is all off bottle the car has never and will never be sparyed

I want to put the auburn carrier in it, with the aluminum cover and moser axles to save the 10bolt and see where i can go with that. if im pulling 10 seconds on a 10 bolt for a season ill be happier then ****, just everyone doesnt think it will happen.

OutlawZ

iTrader: (4)

You ran a 1.4 60' running mid 11's?????? That's one helluva launch for a mid 11 second car..... Most 11 second cars run in the 1.6 short time area.... I'm surprised the 10 bolt lived thru the 1.4.....

96capricemgr

iTrader: (1)

Well I will say it seems that truely hooking is easier on parts than shaking the tires.

Worst parts breakage nights at the local track are the foggy ones where traction comes and goes all through the 60ft. mark.

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iTrader: (5)

ya it is almost 1.4 its actually 1.52 but close enough i say. Nice for only a 2400 stall

but you seem to be really good with these kinda cars maybe you can help me out with this.

I have been running 10 w40 in my 396 motor. Although my mechanic suggested 10 w30 in it and that run smoother. I brought it up to the track and had the needle passed 115 and lost all oil pressure. I did the same thing the next path. Now i do have a oil leak in the front so that could be a small issue but not that big enough to do any damage. I turned the car off waited alittle and drove really slow in the return lanes to the pits during that time the oil pressure was deffently there. Now alot of freinds/LT1 guys are telling me its my gauge because it only happened twice and hasnt happened since. should i be concerned and if so what should i do ?