3.73 with 700R4 or 3.07 with TH350?
 

I've been debating this since I got the truck. On the one hand, I like the thought of a 700R4 and 3:73, truck would be great off the line and still have decent revs on the freeway. But, the setup for a TH350 is much simpler, cheaper, and no mods required. In order to make the 700R4 work right I have to get the TV cable and the lockup solenoid, which adds another couple hundred to an already more expensive transmission.

So what do you guys think? Right now I have a 3.73 posi in the truck, and I just picked up all the brake parts for it. I'd like to commit to the gear before I start installing the brake parts obviously... so wanted to see what you guys think. Would the truck bog off the line and make towing a strain on the trans? I'm trying to keep the costs down since I have a limited budget so that I can actually make it to Power Tour.

I'd obviously have to sell the 3.73 Posi to get the 3.07, but I'm figuring the 3.73 is worth more than the 3.07. Plus TH350's are a dime a dozen.

Re: 3.73 with 700R4 or 3.07 with TH350?
 

The 700R4, in addition to having an overdrive, also has a lower first gear.

In my opinion, you'd be much happier in the long run with the 700R4. If you get a complete donor, you can get most of the parts you need from it. I'm picking mine up tomorrow.

Re: 3.73 with 700R4 or 3.07 with TH350?
 

I have a 700 R4 in my 84, with a set of 3.73 gears in the rear. It makes good combination and I would say that the roadability of that setup out performs the 350 in many ways. Lower RPMs on th ehighway and a good lower end for starting up.

Re: 3.73 with 700R4 or 3.07 with TH350?
 

I would go with the 700R4 and 3.73 gears. I have that combo in my '63 and love it. It has better gearing low and actually turns 3-400 less rpms at (2300 @ 70mph w/28" tall tire) than the TH350/3.08.

Re: 3.73 with 700R4 or 3.07 with TH350?
 

Id agree with the above, 700r4/3.73.
Yeah, it'll cost a bit more up front, but for drivability and efficiency you'll get it back in time.
Also, nowadays that rear is more expensive than the 700r4.
I've got the 3.08 rear I'm going regear to 3.42 and a posi unit.
Trans will be a 2004r. Should let me keep my th350 shaft.
Mine came from a Monte Carlo SS and already has a 25-2800 stall convertor.
I'm not building a torque monster, so it should do fine.
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Re: 3.73 with 700R4 or 3.07 with TH350?
 

i have a 67 with 700r4 in it and has 373 gears and it does well

Re: 3.73 with 700R4 or 3.07 with TH350?
 

I'm running 3.73's and a 200r4 in my 72. I'm running right around 2100 rpm's at 65 mph. Probably 600 less than what I was running with my th350/3.08 combo......

Re: 3.73 with 700R4 or 3.07 with TH350?
 

You have to run the numbers. I am in exactly the same place myself, TH350 just crapped out on me (actually broke the case) and I have 3.73 gears.

First thoughts were just replace it with another TH350 and drop in the 3.08 posi I picked up last year. Looking at around $1000 that route. Thought hard about the 700R4 but kept hearing all the horror stories there too plus the additional $500+ really started making this a stretch.

Then there is the fact that I have a severe distrust of automatic transmission re-builders. Not an unfounded one either.

But the real question is how much you use your truck, how you use it, and what speeds you typically drive it at. There is a payback for the OD trans but it could be months or decades depending on how you plan to use it.

For me, my truck is a useful toy that won't get driven much, will be mostly driven in town but sometimes on the Arizona freeways where you had better be doing 75 mph or get run over ;)
So I went old school with a wide ratio 4 speed M20. Found it on CL for $550 with a Hurst shifter. Flywheel, clutch, bellhousing and stuff for a few hundred more and I'm cooking with gas! :lol:
Will see how it does with the 3.73 gears and will likely try the 3.08's.

Bottom line is that you have to do what works for your situation. I would have probably done things differently if it didn't make sense for me.

Re: 3.73 with 700R4 or 3.07 with TH350?
 

DesertCat,,

Im changing my 68 over to an M20 also. Right now I have a 3.08 open rear that Im planning on changing to a 3.42. I think the 3.08 will be good on the hiway, but will be doggie around town. The 3.73's ought to give you a boat load of torque (youmay have to weight it down!! The 3.42's should give me about 2200-2300 rpm at 65-ish.

Re: 3.73 with 700R4 or 3.07 with TH350?
 

Thanks for the input guys. Here's what I figure as far as RPMs for each setup. I'm using 255/70/15's on my rallys, tire diameter is 29".

3.08 and TH350:
60mph = 2145rpm
70mph = 2360rpm

3.73 and 700R4:
60mph = 1824rpm
70mph = 2007rpm

Now the TH350 rpms will be higher by 200 or so just because of torque converter slippage, where the 700R4 is lockup. So there's a big difference. Basically after Power Tour it's going to be my tow rig / toy. I have always leaned towards the 700R4 just because of the rpms and the fact that I already have the 3.73 rear end. but I find TH350's for like $150-200 every day... and 700R4's once a week at best, and most are 4x4. I don't need the trans yet anyway, but I'm still planning that stuff out. Seems like in the long run, the 700R4 is the best choice, just because it will save on gas on the highway and have a better off the line with the 3.73. if I can budget that, I will. We'll have to see. 3 months to go... :lol:

Re: 3.73 with 700R4 or 3.07 with TH350?
 

I hang in the 60-66 group mostly, but like to see what the 'newer guys' are doing. RE: TV cables, stock TV cables work just fine. And if you wire up your own lockup t-convertor(almost like changing trans fluid), you're spending about $25. So, that couple hundred-figure you used might stand trimming a bit.
HTH,
sam

Re: 3.73 with 700R4 or 3.07 with TH350?
 

I'm running 255's also but around 60 mph I'm turning rite at 2250rpm. At 70 around 2700 rpm. 72-350/350t. 3.08 rear gears. Around 58 mph 12 mpg. around 65 mph I avergage about 9-9.5 mpg.

I'm wanting 700R4 also because this is my everyday runner also.

Re: 3.73 with 700R4 or 3.07 with TH350?
 

if you plan on driving it more than 5 miles in one direction or at speeds faster than 60, you better go with a 700r4 with the 3.73 gears.
Can I ask are you going posi?
You can have the 700r4 can be setup to manually lockup instead of vacuum.....and its only 1 1/2 inches longer on the mounting.....and our trucks are pre-drilled to move the tail mount back to accommodate the 700r4.

I had the TH350 behind my original 350SBC and a 12bolt 3.23 one legger diff. I built the 12 bolt rear up with a EATON full posi 3.73 (1000HP capability) dropped in the 700r4 with Manually lockup giving me major torque in first gear, quick shift up to 2nd to push into 3 and 4th that have final drive 3.05 hwy gears and corvette shift kit.......put all this behind my Vortec 350 (modded) I am pushing almost 380hp to the rear wheels and can drive 30 miles away on the hwy reaching over 140mph......
Now no matter what you do a th350, you wont reach those speeds without taking it down a 1/8 mile track and then shutting down.

Re: 3.73 with 700R4 or 3.07 with TH350?
 

I am starting this swap this week got trans. yesterday,been trynig to grab the parts I need the last month.I haven't figured out what tv bracket I need I switched over to a 71 cable accelerator cable that uses the rear carb bolt.JEGS and Sumitt both have brackets but in the fine print I don't think they will work.The bowtie overdrive setup is nice but to pricey when I know something simple will work what are u guys running

Re: 3.73 with 700R4 or 3.07 with TH350?
 

I got the edelbrock brackets and very happy with them. Dont forget to get the carb adapter. Edelbrock 8036 for the cables, I added a couple of holes to move the cable closer to the carb. B&M 64511 for the carb adapter. Holley has one also, but I dont run Holley Carbs.

Smitty

Re: 3.73 with 700R4 or 3.07 with TH350?
 

I'LL GO CHECK THEM OUT,I am running an EDDY carb along with a 1" spacer

Re: 3.73 with 700R4 or 3.07 with TH350?
 

I have a 1406 with a spacer and have no issues. I can send you pics when I get home, but its going to be about three weeks, Im in Alabama for school....

Smitty