700R4 with a 373 Rear
- Thread starter Jsup
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JPhil
Huh?
Couple of my hot rod buddies run that setup in their big block Camaro & Chevelle. They like the deep first for launching & great burnouts. They run 3000 RPM stall, and live for drag racing, but these are street cars.
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bobs77vet
Well-known member
i think this would be a great combination, i have the 700r4 with the 3.07.....you are thinking about first gear.....but the real test is when you are in lock up and still in fourth gear.......at 1100 rpm at 40 MPH its way too low. i am in fact toying around with this gear ratio. first gear will definitely be a blast because it is now with the 3.07 . the math i would be doing is for these two situations....... what is the RPM at 70 mph and what is the rpm at 40-45 mph because thats when the 700r4 wants to down shift. so you want to be in your torque band at 40 mph and not too high of an RPM at 70.
bottom line is i think you are in the ball park with a 3.73 i dont think i would go higher. i wonder what the rear end ratio was for the cars they stuck hese into to begin with.
mrvette
Phantom of the Opera
Well my '87 vette had the 308 rear, as I recall, pretty sure...it was a vert with aluminum heads gone some 15+ years now...never messed with the rear anything much...the 700 in there seemed well suited to the L98 torquey engine, but with a cammed up engine, and higher idle like I have now, I was having problems with WAY premature shifting outta the 336 rear in this shark....not across the intersection and into second....this engine was 1/2 to boggsville, injection or not...thing is, I did the L98 on top of the rebuilt L48 that was in the car...no cam in it....just a nice 600 rpm idle....Muncie...
I got a line on a '89 truck block all fresh with new parts for like 1200 bux...had it assembled for another 300, tossed heads on it for 300 maybe, then got the 700 built.....WAY overspent on a cam for it....had nothing but trouble since....
finally maybe maybe maybe I may be getting down the end of the troubles...
Jsup
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I'm running a 3000 stall.
big_G
Blown Member
The '82 and most all cars with a 700 are high 2's to very low 3's. Even my C-5 auto with the performance axle ratio was only 3.15.
TimAT
Addict, Cruise-In Bird-Run 1 Veteran
Just doing the math- 3.73 rear + 6.12 low = 9.58 gear in low. If that won't launch it it's tied to a tree. A good shift kit will let it hold 1st gear a bit longer at WOT.
It's also possible to tailor the lockup with a pressure switch on the 4th gear pressure, but you need to be IN the torque curve or it'll shake like a possum passing a peach seed.
It's also possible to tailor the lockup with a pressure switch on the 4th gear pressure, but you need to be IN the torque curve or it'll shake like a possum passing a peach seed.
Twin_Turbo
Der Maulwurf
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It sucks, 82 here w/ those gears and a 700R4, 1st gear is completely useless.
JPhil
Huh?
But it'll do great smokey burnouts forever, won't it?
3.08 1st with 3.73 diff = 11.48 overall 1st. Shift to 2nd about halfway across the interesection. I personally do not like the 700R4 gear ratios, but as I said, my drag racing hotrod buddies like it fine.
bobs77vet
Well-known member
my only gripe with my 700r4 set up is the low speed issue in 4th with lockup engaged when you are decelerating/merging etc.....at about 40mph i am still in 4th and the rpm is way low at a fast idle speed. and even with my 350hp/425 ft lbs motor i am under the beginning of the power curve, so what i wind up doing is manually shifting it into 3. i am running a 2500 stall.
mrvette
Phantom of the Opera
Like I said I love my 200 4r so much better than that 700 I had there, not only is first gear much better, it shifts when I want it to, a-la Trans GO, and then the thing holds WOT in O/drive....something the 700 refused to do....
:crap:
:crap:
Jsup
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Yeah, but the conversion is a bitch. I did the cheapest, easiest thing that should work. I think with my motor the 700 should be fine.
rabiddawg
Well-known member
I too have the 3.07 like Bob, but I have a hydraulic lock up (instead of the electric)and 3000 stall. I am very happy with the way my car behaves and have not noticed any of the lugging that several folks are dealing with.
It does shift 1 -2 very quickly but I can always pull it into 1 and shift it myself if need be.
It does shift 1 -2 very quickly but I can always pull it into 1 and shift it myself if need be.
Jsup
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I have a 3000 stall too, what's your cam like?
I have a 700R-4 with 3.70 rear gears. 1st is definitely good for burnouts. Just don't do it on a dusty road. Two weeks ago my throttle stuck wide open as soon as I started to move on a dusty road in front of our shop. The car went immediately uncontrolable and slammed itself into the curb, bending the right lower rear control arm mount in the front, ruining both pass side wheels and bending the pass side trailing arm. I have a 2500 stall converter and unless I'm really into the go fast pedal it has great street manners. At 65 MPH it is running about 2100 RPM.
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bobs77vet
Well-known member
AJ77 what is the rpm at 40-45 mph......just before it does the down shift to 3rd? i think i am at 1700 rpm at 65 with the 3.07
gr8vet
Well-known member
Yep, I thought it sucked so much I'm putting in a T5. 
. There is just something wrong to hit the throttle and your transmission shifts into second at 10MPH. And I was even using the "little secret spring" adder to further adjust shifts. Have a friend that did the 200 in his 78. Said it was not bad at all. Good luck!
tt
. There is just something wrong to hit the throttle and your transmission shifts into second at 10MPH. And I was even using the "little secret spring" adder to further adjust shifts. Have a friend that did the 200 in his 78. Said it was not bad at all. Good luck!tt
@45 MPH it is about 1300 RPM. It's borderline a problem cause it's still in lockup and sometimes starts to buck. @ 40 I just put it in 3rd cause it is only about 1000 and the cam I have doesn't like it below about 1600-1800 RPM. I have a Crane roller with 222-236 duration and .518" -.539" lift with 112* lobe separation. The engine doesn't start to smooth out till I hit around 60 MPH and 1800 RPM. I was wrong in my last post---@ 65 it's @ 2000 RPM instead of 2100.
Jsup
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You can tune that out and make lockup any speed you want.
Yea I know. I just don't want to open up the dash to get to the wiring again. With the old system, I had the lockup wired to automatically occur on shifting into 4th. When I installed the Accel system I didn't feel like changing the wiring at that time, so I just left it as it was. If I get bored sometime I will re do it and program it to lockup at a higher speed. I hadn't been able to successfully drive the car for about 3 months and just wanted it to be on the road again. I don't remember seeing a harness for a vehicle speed sensor in the Accel wiring, so I'm not sure how that would work? I may have to look into that.
