Hi, I have a 93 firebird with an automatic tranny. I'm pretty positive it's a 4l60 which is the same thing as a 700r4. From what I understand the 93's got the 4l60 and the 94 and up's got the 4l60e... correct me if i'm wrong. Anyway the tranny that is in the car shutters in overdrive when I step on the pedal at a certain rpm... and something about the tranny just doesn't seem right to me when it's in overdrive. I was thinking of swapping it for a turbo 350 because from what I understand they hold up a lot better. I was wondering if any of you guys could give me some tips on this and if you've done this swap yourself please tell me what you went through.
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Injuneer Fred has a TH400 in his 94 Formula.
Actually, I'd recommend a mildly modified 4L60E replacement. This way, the install is no big deal and you keep the overdrive. The 4L60E will hold up quite well when built properly.
Gordon
www.provenperformanceconcepts.com
Gordon Arnold - '00 WS6 T/A - Sold -
Depends on what you use the car for. TH400 and TH350 are 3-speed automatics, with no OverDrive. With my TH400 and 4.10 gears, on street tires (25.6") it was buzzing along at almost 4,000rpm at 70mph. Not good for a caily driver. A Gear Vendor O/D unit helps, but now you've doubled the cost of the conversion.
4L60 in the 93 is essentially the 700R4, as you pointed out. You have to use a non-computer controlled tranny, so the 4L60E isn't going to work. What kind of HP are you making? Art Carr can sell you a 700R4 that is good for maybe 750HP. He claims its good for 1,000HP, but a friend of mine proved that wasn't true....
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Fred
381ci all-forged stroker - 10.8:1 - CNC LT4 heads/intake - CC solid roller - MoTeC engine management - 8 LS1 coils - 58mm TB - 78# injectors - 300-shot dry nitrous - TH400 - Gear Vendor O/D - Strange 12-bolt - 4.11's - AS&M headers - duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP/800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117MPH straight motorComment
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Hey Fred, that wouldn't have been George would it?
How do you like the gear venders OD? I'm thinking about a TH400 with the OD swap for my GN.
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When my trannie goes (and it will, its the last weak link) I will be doing a TH400 w/Gear Vendors overdrive...but then again...she is no longer a daily driver.
You can get 700R4s made to be nearly bullet proof, but I am going with something thats been proven to take a LOT of abuse.
It all really depends on what your intentions and HP requirements are for the car...
KnightFireComment
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You could try the TransGo
You could try the 700R4 TransGo shift kit. Fixed a few problems in my friends 93 Formy. We found alot of things about why his tranny was having problems. One of the servo parts was actually shattered for some time. The 700R4 kit was more work than the 4L60E shift kit, but the improvement is worth it (eventhough he only went with 2 washers)1995 Firebird Formula
(A4 3.23)Ram Air w/ K&N, TransGo Shift Kit w/3 washers
,SLP~Shorty headers, LoudMouth, Air Foil, LineLocks. Catco Cat. Hypertech 160. TB Bypass. MSD~8.5mm. Walbro 255lph. FT MAF ends. LT4KM. BMR~Adj LCA's, Rear sway, Panhard rod. HAL QA1 rear shocks. Random Tech adj TQ arm. Nitto NT555R's. Covered in Zaino. 13.466@103.85 N/A. [1.948 60' 
13.410 @ 102.66 11/20/05]Comment
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Hey fred... i was checkin out the pics of ur car and i noticed the pro stars... what size are they like with backspacing and all?Comment
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Weld Pro-Stars:
Front:
15x3.5, 1.75" BS. Requires 5/16" spacer plate to allow wheel to clear the clip that holds the pads on and the big horizontal arm on the steering knuckle that the calipers rest on. Requires 2.67" knurled 12mm studs from LPE or GMPP to meet NHRA tech.
Rear:
15x10, 7.5" BS. Requires grinding the corners off the fins on the brake calipers. Requires longer studs, as above, or I have 1/2" x 3" screw in studs in my Strange.
Fred
381ci all-forged stroker - 10.8:1 - CNC LT4 heads/intake - CC solid roller - MoTeC engine management - 8 LS1 coils - 58mm TB - 78# injectors - 300-shot dry nitrous - TH400 - Gear Vendor O/D - Strange 12-bolt - 4.11's - AS&M headers - duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP/800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117MPH straight motorComment
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That shutter is probably the lock up clutch shuttering at highway speeds. It may be able to be fixed without pulling the unit out.
If it does have to come out, the 4l60 can be built pretty well. If your driving on the street, I wouldn't go to a TH350. I swapped out my 4l60e for a T56 6 speed. If you have a donor car, its not a bad job - it took me a weekend to do it. It holds up alot better and is much more fun on the street I know a guy in PA who sells the whole conversion for a reasonable price. I paid 1300.
If you do swap in a 3 speed, at least go with a truly bulletproof unit like the TH400. The 350 would be a waste of time.96 WS6 Formula: Ram Air, 383 Stroker, Ported LT4 Heads and Manifold, 1.6 Crane Rollers, 58MM T.B., AS&M Headers, Borla Exhaust, Meziere Elec. H2O Pump, Canton Deep Sump Oil Pan, 100 HP OF TNT N2O!! , T56 Conversion w/ Pro 5.0 shifter, SPEC Stage 3 Clutch, Hotchkiss Subframe Conn., Lakewood Adj. Panhard Bar, Spohn Adj. LCA's, BMR Adj. T.A., Custom 12 bolt w/ 3:73's, Moser Axles, Eaton Posi, Moser Girdle
11.6 @ 123mph (1.6 60' - getting there
)
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Thanx for replyin everybody... u've given me some awesome ideas... i think im gunna start saving some funding for the art carr 4l60 lol... the gear vendors would be awesome but i don't wanna break my bankComment
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