Suggestions for a better highway cruising set up..

[McCall72]

I'll come right out and say that ratio's and gears are not my bag, and I'm pretty ignorant on what should match with what. Right now my current set up is stock 350/350 auto with a 2:73 rear end (if my memory serves that is the stock rear gear). I'm looking to switch to something that cruises at a little lower RPM on the highways and would like to try to avoid yanking the tranny if possible. Are there any good rear gear set ups that can lower the rpms a little without having to change the tranny to a 4 speed?

[CrazyDavey]

No doubt you are going to get a ton of information from members on your request. To clarify do you mean you want quicker acceleration from stop? If so you want a "lower" (a higher number like 3:25, 3:42, 3:55, etc.) gear which will increase your RPM's at cruise. You already have gears that will give you low RPM's at cruise. A 4-spd doesn't really enter into it. Hope that makes sense. David

[McCall72]

Thanks for the info. To clarify, I want lower RPMs at a highway speeds at 70 mph and up I don't have much of a lead foot so launching at stop lights is not really a priority for me.

[Shadow Gray SS]

I just did a quick search at Summitt and you have a tall a gear

as they offer. I believe the only taller gear is a 2:56, could be

wrong on that though.

 

Without pulling the tranny you could add a gear vendor OD, but I

think you would want a shorter gear to accomodate the OD final ratio.

[CrazyDavey]

Ditto what Jake said.....the other option would be a trans with an overdrive built into it like a 700R but that would require a swap and mods...

[monte70car]

The only real mod to make is a shorter drive shaft and make sure to use the 350 yoke at the trans. The 350 yoke is stronger then the 700 one. Another OD trans to look into is a 200r4 the gear ratio is a lot closer then the 700. By going the 200r4 you will need to change the yoke but keep the same length drive shaft. Arron I run a 700r4 with my stock 2.73 gears 70 mph I turn roughly 1900 rpms in OD. You could also look into different size tires which should bring the rpms down right guys?

[McCall72]

Sounds like maybe the 700r4 is the way to go here...I've done some preliminary searches on Craigslist in my area and found that you can pick one up fairly cheap...anything I should be looking for such as certain years or will pretty much any year 700r4 work, and how about stall converters and such?

[kc8oye]

much more work!? you have the driveshaft shortened by 6" and you are done, everything else works.

 

I had to call around a little bit to find a machine shop equipped to do driveshafts, but once I Did, I asked them how they wanted me to measure for the driveshaft.. every shop is different, but they had me measure from the center to center of the ujoints on the two yokes (Trans and diff) and then they cut the shaft down to those specs for me.

 

if you get a 700r4 from a pickup truck, you will have no problems as they are designed for a heavy truck :>

 

if you have a console/floor shift, you will need to change out the 'gate' for the shifter and the lens, if you are column shift, it will work fine all though the indicator in the dash won't mean much any more ~

 

just slide the crossmember back to another set of holes and you are done!

 

 

I run 3.55 gears with my 700r4 and I cruise at 2250 rpm @ 70mph and I generally wouldn't recomend you go much less. i wouldn't go lower then 2000 even with a big block.

 

i had a local shop rebuild my 700r4 with all the performance goodies too. Shift Kit, Kevlar band, hardened input drum, corvette servo, 2500 stall converter etc.. $1200 to have him pull the trans rebuild it and put it back in for me.

 

If you run a Qjet carb, you shouldn't need to make any mods for the 700r4's TV cable. If you run a holley, there is a bracket from holley that will take of you, plus you need the 'kick down lever kit'

 

I forgot to add.. stay away from early 700r4's.. IIRC, you want the 1986 and later 700's.. the early ones had a lot of issues

 

[Ian]

If you are looking at the 700R4 you want one out of a 87 or newer Camaro as they changed them to 30 splines where the converter hooks up. I have a 88 on the floor waiting to go in, but you will need the different parts to make it work. I got mine for free so it will help offset the cost for me. I am going to have it rebuilt before it goes in. For gears if you change to a higher number the RPM will go up at cruise. I went with 3.42's. I can't tell you how well they work on the highway yet, but from what I have read they should be nice all around.

 

 

[kc8oye]

even better would be an 87 corvette because they had the more performance oriented shift patterns :>

 

[DavidTX]

First you need to consider several things:

Why do you want to cruise at lower RPM on the highway? Better gas mileage or ?. You may or may not get better mileage. It depends on carb, cam, heads, timeing and numerous other factors. If you are driving in an area with a lot of hills, you might have difficulty maintaining constant speed without the transmission downshifting.

You will get better mileage with a transmission that has a lock-up torque converter. It also prevents heat buildup from that slipping torque converter.

I thought it might be helpful to consider these things in case you had not previously thought about them.

[Winston Wolf]

I think you are asking for issues with a 2.73 gear and an overdrive transmission. This will help you, as I don't know your actual tire size.

 

Tire/Gear/MPH calculator

 

If you don't care about acceleration or how quick your car is, I would just stick with what you have. Swapping out transmissions always costs more than you plan for and it seldom works out without some minor installation issues. If you change your tranny, you should probably go to a steeper gear too, so it will start to get costly.

 

 

[monte70car]

Here is some thing else to look at. We have two big block cars 57 Nomad(gen VI motor) and the 70 Monte(mark IV) both cars have the same 700r4 trans right down to the stall. Gear wise the Nomad has a set of 3.70 gears and the Monte has the 2.73. The Nomad with its 3.70 gears went on a 73 mile round trip, started off Saturday morning with 3/4 of a tank by the time we got back home we had a 1/4 tank. Now the Monte with its 2.73 gears did not go on the same 73 mile trip but it went on a 16 mile round trip, it started with the same amount of gas as the Nomad 3/4 tank made it back home with 1/2 a tank.

 

Rpm wise the Nomad was turning about 2000 rpm with 295/50 under the rear. The Monte was turning about 1500rpm in local traffic. The Nomad had it made since it was on the highway.

monte 255/50/16(2.73)

45mph 1,110 rpm

50mph 1,233 rpm

55mph 1,357 rpm

60mph 1,480 rpm

65mph 1,603 rpm

70mph 1,727 rpm

 

nomad 295/50/15(3.70)

45mph 1,472 rpm

50mph 1,636 rpm

55mph 1,799 rpm

60mph 1,963 rpm

65mph 2,126 rpm

70mph 2,290 rpm

[McCall72]

Thanks for all the info folks.

[stangeba]

If / when my 350 4BBL THM350 trans needs work, I will go to an overdrive like mentioned above. All or most cars built since the mid 80's have had Over Drive in them.

Bruce

[Shadow Gray SS]

I have a 700r4, BB & 3:42 rear.

 

For the tranny the crossmember had to be moved back, the driveshaft

shortened, new fluid lines fabricated, installed external cooler &

highly recommend you do the same & my console shifter works w/out

mods.

 

At 70 I run about 2100 rpm. My mileage has not stabilized yet, still

breaking in. This tank looks to be about 11mpg, but I loose

control of my right foot every time I am in the Monte

 

Go here and peruse some. They are pretty helpful

if you call also.

[Chevyss]

Like Jake; BB w/700R4 3:73 and I've checked mileage at 17 at 60 mph. The lock up converter is great. I'm still at the top end of the break-in period. The Monte cruises real well. I too have a lead foot when it comes to the Monte around town.

[Sam (Bones)]

I would consider the 700, it has a deep first gear and with the weight and the 2.73 axle, I think it would be a wise choice with your combination

[Shadow Gray SS]

Arron I run a 700r4 with my stock 2.73 gears 70 mph I turn roughly 1900 rpms in OD.

 

I was thinking it would be much less for some reason. That would be a great cruiser.

[monte70car]

Jake it is a great cruiser. Last year we came back from a show in it running 60 mph all 4 windows radio playing(vol at 13) and you could still talk to each other. We even went flying by a newer Vette which I'm sure was doing 65mph. Heck the Nomad ain't a bad cruiser either but that's another story.

[kc8oye]

you really don't want to use such low gears with o.d

the trans will want to shift into o.d around 45-50 mph depending on its calibration and with the 2.73's that's just _WAY_ too low.

 

I really wouldn't run less then a 3.36 maybe 3.08's.. but that's pushing it. and like it was said before.. consider where you make power.. if you have a high strung small block for example, it's not going to like lugging the car along at nearly an idle.. but a very mild big block problaby wouldn't care.

 

I have 3.55's with my 700r4 and at 45mph I'm barely doing 1500 rpm with the converter locked, in fact, I Rarely lock the converter around town (I use a manual switch) because it makes the engine lug and dog too much when it's in o.d at low speeds.

I'm running 2500 stall btw.

 

if you really want those super low rpm's at 70, I suppose you can manually shift into L3 with the 700 to keep it out of o.d but then you have to deal with engine braking.

 

I have a pretty mild 350.. and I run 2250 rpm @ 70 and the engine _LOVES_ it there... i wouldn't go a whole lot lower .but that's just me.

 

[Phil]

What are you talking about TIM IS BANNED?

[Andreas]

Temporarily...

 

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[BuffaloBillPatri]

Try some taller tires on the rear. Cheap & easy. You can then decide if dropping the highway RPM's is "better"