Hi, I have an 84 Z28 and just took the 305HO out and put in a built up 327. My 700-r4 cannot hold the power or torque of my new engine, so I put in a th-350. I already have the torsion bar attached via a bracket, but my th-350 has the 6 inch tailshaft, making my 700-r4 driveshaft too short. I know I can either lengthen the driveshaft(but by how much?) or can I just use a stock th-200 drivshaft?? And another question, please tell me all you can about the vaccuum modulator on my th-350, it's a 70's one with NO computer on it, if that helps any. Thank you.

 

Since the 6" tailshaft is too short and the 9" tailshaft TH350 works fine, I'd say you need to lengthen the driveshaft 3".

The vaccum modulator controls the upshifts depending on manifold vaccum. Without it, the tranny will not upshift.

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But can I use a stock TH-200 driveshaft???? instead of lengthening mine???

 

since when can a 327 overpower a 700R4?

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91 RS W/carbed 350, Vortec heads, performer rpm, Comp cams Xtreme energy 280 grind. BFG Drag radials. 3.42 posi,Corvette servoed 700r4, ****ty stock converter
13.24@104

 

I'll tell you when a 327 can overpower a 700-r4. First of all, it is an 84' 700, which means that it is VERY weak, now if it were post 87, then it would be more powerful. Secondly, it's a 327, but I had it machined, so it now has a new 350 crank, and a .040 overbore. that's a 357 now. edelbrock performer RPM intake, edelbrock 600cfm carb, 489 cam, 2.02 #461 camel hump heads, aluminum roller rockers, new valvetrain, and keith black pistons. The machinist said it would make at least 350 horses, and the torque would tear up a 700-r4. THAT'S WHEN A 327 CAN OVERPOWER ONE!!

 

I think youre right about the pre '84 piece of sht, but I know that my 700R4 holds up fine to my engine......which as you may have seen is no slouch, and I've seen these trannies hold 12 sec cars w/o a problem.

 

cool engine choice...ok here goes THe modulator controls the part throttle shift points....you will want to hook it up to manifold vacuum source...this means the hole in the back of the manifold that suxs all the time.The vacuum modulator works like this......low vacuum later shift....high vacuum early shift.....NO vacuum and the trans will not go into 3rd gear and hunt all the time. I once made a adjustable vacuum control by taking a air vavle from a fish tank and putting it in the vacuum line to lower the vacuum signal to the modulator to get a firmer shift...worked purdy good ...and i think B&M used to offer a similar kit.I've rebuilt about 1000 350's so if ya gots questions let me know...later

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87GTA,350,Auto,MAF screens removed,195 thermostat,cold start injector UNPLUGED,K&N,modified air intake,ADSchip,3:73s,3inch cat back Flowmaster single outlet,TPS.54,Bosch Plat plugs,base timing 6BTDC,22 MPG and runs like a bear,Bilstiens in the rear....,don't let yer meat loaf

 

back to my original question, will a th-200 driveshaft fit my th-350? remember, 6 inch tailshaft th-350.

 

Yes 'chicksL69'.
I've done it with a 200C to 350(6" shaft) swap. Fits perfectly !
The only problem I had, was the shift cable bracket down on the trannie. I was only able to get one bolt on the pan to hold it on, but I just picked up a Megashifter, and it comes with the bracket I needed.

Good Luck,
Ron C. Terry




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'82 Trans Am
'81 Camaro Z-28
'94 Vette LT1 Coupe

 

2-3 "hunt" WTF??!!

WHAT ARE YOU SMOKING??!!

The modulator controls shift timing and feel- low vac = later shifts (all the way to 3rd), high vac = earlier shifts.

TH350s also have a kickdown cable (yours was probably misadjusted) that controls the 3-2 kickdown, it looks like a TV cable on a 700, but instead of controlling shift quality/feel, it only controls kickdown (hence "kickdown" cable).


Also, with no vac on the modulator the tranny WILL SHIFT!

CRASH COURSE IN TH350 SHIFTING:

3 things control shift quality/timing.

Modulator
Govenor
Kickdown cable/valve

(this also applys to 700s, only the kickdown and modulator are replaced by the TV (throttle valve) cable)

Modulator = engine load

Govenor = road speed

Basically you've got modulator pressure on one side of the valve and govenor pressure on the other side of the valve.

Modulator pressure will hold the valve closed until govenor pressure equals or exceeds modulator pressure and opens it.

You can tune the govenor with different springs and counter weighs to change the pressure at a given speed, and you can adjust the modulator pressure with different modualtor pins (VERY TRICKY) or by turning the adjustment screw inside the vac port on adjustable modulators (pretty simple if you know what you're doing).

Kickdown basically boosts the pressure on the modulator side of the valve to force it to close and kickdown....

There are a few other variables, but that's basically how it works.


Oh, and yes, you can use a 200c driveshaft out of an F-body with the shorty TH350.


Hope this helps,

John (Ex- AAMCO certified diagnostic tech & installer)


Note- if you've got a bad govenor, checkball missing, valvebody gasket leak, leaking valve, mis-drilled seperator plate, etc. you might have a problem with the upshifts and downshifts, but if everything is working properly you WILL have upshifts with no vac on the modualtor, they will be VERY late, and VERY HARD!

Viseversa, if you have a collapsed vac hose on the modualtor (trapping vac in the modualtor) you will have early soft (or worse, slipping) shifts (a GOOD way to burn up your tranny).

[This message has been edited by 812MANY (edited October 17, 2000).]

 

Shoulda kept the 700, man. It'll hold up fine to that engine if built even half-way decently. You are gonna miss that overdrive SOOOOOOOO bad that I bet you'll switch back within a month anyway.

I love TH350's, don't get me wrong, but only for 450 (or more) lb.ft of torque... Your mileage will SUCK without OD... my $.02

Have fun with it, though. Got a shift kit in the 350? They shift MUCH better than a 350 IMO with nice rebuilds and shift kits installed. Rear-end wrecking/u-joint breaking shifts are AWESOME!

FYI, The TH350's I have had DID NOT shift w/o vacuum hooked-up to the modulator...

[This message has been edited by FastBroker (edited October 17, 2000).]

 

Yes, I did put a b&m shiftkit in the tranny, I used stage 2. I wanted to use stage three(I LOVE very hard shifts,) but I was scared that stage 3 would have me shifting at 8 grand. not what I want for a street car. the only prob I might have is that B&M was'nt specific whether I should use their seperator plate on stage 2 or if I should use the stock one, so I threw in the b&m one. any clues on if I was right?? thanks everyone for the info, keep it coming if you can!!!!

 

oh yeah, and i would have kept the 700, but it's an 84 version, which you should know, suck! if it was post 87 then I would have kept it, and paid for the overly expensive 3000 stall that I had to buy for my cam. so yes, my th-350 has a 3000 stall right now. again, thank you.

 

B&M shift kits don't have a "stage 3", and the 700 TransPaks don't have a stage 3, but the TH350 TransPAk has stage 3. Did you use someone elses shift kit in TH350 or did yo use the TransPak???

[This message has been edited by FastBroker (edited October 18, 2000).]

 

Yes, I used the b&m "transpak" for my th-350. sorry if i was'nt specific, I call anything that makes your tranny shift different, a "shift kit"

 

You & I have almost the exact car, actually yours is the first thirdgen that I have seen w/ the 327.

I was wondering if your torque convertor is a lockup or non-lockup. I need to install the higher stall on my car but I want to go with a lockup setup. I am currently looking for some help in this area and I am not getting anywhere. My trany is too an old one from the 70's and I am lost to how to control a lockup TC.

By the way Good choice switching the trany. It only took my 327 2 months to tear the 700r-4 up.

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'84 Camaro w/ Large Jouranl 327 bored .030 over; 3.73 geared Auburn Limited Slip Diff. FlowMaster Muffler w/ Shortie Headers. TH-350 Built Trany Underneath B&M Mega-Shifter. Many Engine compartment Dress Up Mods. Edelbrock High Flow Water Pump w/ Flex-a-Lite Cooling Fan.
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