Just got 700R4 Installed!

[fleetsidelarry]

Originally Posted by purebred

Appreciate the info, I know the wear and tear on the engine and lower gas mileage is a plus but I think I will stick with my 350 for awhile longer. I just don't do that much freeway driving to justify the switch, I do alot of stop and go, that the 700 wouldn't make that much difference anyway.

well, it will get you rolling easier and accelerate a little quicker off the line, too (check the 1st gear ratios between the two) but, yes, if the money's not there right now, your point is well made. I spend a lot of my time in the 45 mph zone where most of the time I keep it in 3rd (1-to-1, same as your high gear). even brief runs on the interstate are awesome, though. I'm staying with traffic at less RPMs than you're turning at 60. it's just NICE

[brokenspoke]

Originally Posted by purebred

Before gas started to rise like it is now I was completely satisfied with my turbo 350, I drive a short distance to work and at 60 with my 307 rear end I am turning 2500 rpm's. I don't know if I could justify the expense of a 700 conversion now. If I ran mine open on the road more I am sure the conversion would be worth it but short distant drives, my 350 seems fine for now, I could probably use the extra money more wisely in a brake conversion, AC install or some other install to make driving more bearable here in the Texas summers.

A overdrive with your rear end gearing will hurt your mileage....

[hd74]

have you got a 700r4 trans ?.iam a none beliver in you will get worst mpg.worst you would have to do is change your cam ,but i think none of this will be nessary .just enjoy quicker pick up higher top speed and better mpg.

[fleetsidelarry]

Valid point brokenspoke, however, saying it WILL hurt mileage is a pretty broad statement, since there are so many factors involved.

first of all, the great thing about this setup is you DON'T have to drive in OD. If traffic speed or conditions such as towing warrant, drive in DRIVE, same as the 350TH. In SS317's case he changed from a powerglide, so he's going to gain no matter what, is my bet.

secondly, the shape of the power band of the engine matters. smaller engines, and those tuned to perform in higher rpm ranges, are more susceptible to "lugging" with tall gears. a 230 six, a 283, or a 350 cammed to operate in the 3-6K rpm zone are going to be more likely to suffer (although I'm not sure it matters in the latter example)

I don't think a 350 or a 454 is going to suffer

[hd74]

http://www.gmtruckhq.com/?q=700R4-4L...n_History.html

[64fleetside]

A 350/700r4 with a 3.07 rear will lug that engine pretty badly, will likely give less MPG. It will work, but seem doggy. 3.42 is about the limit when using an OD trans. You will also find accelerated flat-tappet cam wear at low cruise RPMs-the engine does not run fast enough to lube the cam well enough.

[likaroc13]

Originally Posted by fleetsidelarry

first of all, the great thing about this setup is you DON'T have to drive in OD. If traffic speed or conditions such as towing warrant, drive in DRIVE, same as the 350TH. In SS317's case he changed from a powerglide, so he's going to gain no matter what, is my bet.

sounds like that's what i'd need to do as well

Originally Posted by 64fleetside

A 350/700r4 with a 3.07 rear will lug that engine pretty badly, will likely give less MPG. It will work, but seem doggy. 3.42 is about the limit when using an OD trans. You will also find accelerated flat-tappet cam wear at low cruise RPMs-the engine does not run fast enough to lube the cam well enough.

i specifically switched to a '72 rear with 3.08 gear to help with highway driving with my Powerglide...it would be nice to not have to switch anything out, especially considering the rear was just rebuilt....when the time comes to swap to 700R4, why couldn't you just do as mentioned above and use DRIVE instead of O/D in around-town situations?

[hd74]

i use a toggle switch to lock up and unlock the tq convertor. if you do not have oil pressure at 1500 to 2000 rpm you have got other problems .i have a 307 rearend with a 700r with a 454 it runs the same rpm as my 2006 gmc on the hwy. the second best thing i have done next to power disc brakes ,you can drive in todays traffic .mine is a daily driver,if you just drive on a few weekends and short distance stick to the old 3 speed trans.if you use it replace with a overdrive its like a 5 speed .iam done on this subject.thanks

[fleetsidelarry]

Originally Posted by 64fleetside

A 350/700r4 with a 3.07 rear will lug that engine pretty badly, will likely give less MPG. It will work, but seem doggy. 3.42 is about the limit when using an OD trans. You will also find accelerated flat-tappet cam wear at low cruise RPMs-the engine does not run fast enough to lube the cam well enough.

I personally do not agree on either point.

but I'm open minded.

I'd like to hear from guys who are disappointed in the switch to an automatic OD transmission 'cause it lugs, and I'd especially like to hear a technical explanation of how the cam is not being oiled sufficiently at a low cruise rpm as opposed to any other load at that same rpm and examples from members that this has happened to.

might be worth taking the cam wear statement over to the driveline and engine forum here. I might even take it to the ChevyTalk performance forum 'cause I like to hear, and learn, more.

[gofastnut]

Liking this thread! I've got a couple of (car) buddies who have switched from TH350 to 700R4 and have been thrilled. One guy had 3.55's and the other had 3.73's the 3.73's are a little deep for hiway driving, but pretty good for 1/4 mile.

[fleetsidelarry]

gofast, yes, both those gear ratios are good all around gears, better acceleration at the expense of higher interstate rpms. best to have posi or you'll wear out a tire real fast

[brokenspoke]

Originally Posted by gofastnut

Liking this thread! I've got a couple of (car) buddies who have switched from TH350 to 700R4 and have been thrilled. One guy had 3.55's and the other had 3.73's the 3.73's are a little deep for hiway driving, but pretty good for 1/4 mile.

3.73 o 3.55's are pefect IMHO....I swaped out a 350 for a 2004r with a 3.08 rear end ...my mileage went down and the engine lugged ..I changed gears to a 3.55 and my mileage went to 22 MPG...my experence

[purebred]

All in all I am satisfied with my 350t, 350 c.i. combo, I have a light cam, Edelbrock 600cfm, headers, It runs pretty good and the mileage although not great is still not to bad for how I drive it, only drive it to work 4 times a month and cruise whenever posible. I guess I will invest in something that will satisfy Me more than a 700. Thanks for all the input.

[fleetsidelarry]

Originally Posted by brokenspoke

3.73 o 3.55's are pefect IMHO....I swaped out a 350 for a 2004r with a 3.08 rear end ...my mileage went down and the engine lugged ..I changed gears to a 3.55 and my mileage went to 22 MPG...my experence

brokenspoke, thanks for clarifying. I didn't mean that what you said before wasn't possible, only that a blanket statement implying that it would always be the case was a bit all-inclusive. I could be wrong but there are probably cases both ways and I think it depends on the nature of one's driving pattern

anyway, if the OP is happy then it's all good

[DoubleL]

Originally Posted by SS317

I looked all over and read a ton on this site about the whole job. I looked at bowtie overdrives and many others, and finally decided I didn't need a transmission way overbuilt for how I drive the truck.

I found a local guy that has his own shop, has been doing transmissions for years, and his shop is always full. He constantly has new vehicles in and out of his shop. I got 4 quotes for the job and my guy was the only one who could spout off most of the things brought up on this site by memory.

I have had my 700r4 for about 3 months. I have 4:11 gears but will be swapping to a 3:73 posi I aquired. Did you use the original shift column?

[chevyguys]

I am running a 700R4 with 3.73's and 27 inch tires. Quite honestly this setup is sweet. I have zero complaints and the truck is a blast to drive. Rpm's are 2300-2400 at 75. The motor just hummmmmms. Don't care about fuel mileage since it's better that my 07 Dodge RAM HEMI by a long shot.

Purchased the trans from Gearstar, they included everything ( cooler, TV cable, torque coverter, synthetic trans fluid, inspection cover, dipstick, kickdown switch) The only thing I had to buy was the geometry corrector for the carb. They even included the correct speedo gear for my gear ratio and tire size. Great guys to work with. 1500.00 delivered to the door with a three year warranty.

[luvbowties]

Originally Posted by SS317

With the power glide gone I'll be happy with any increase. I drive this truck all day pulling my landscaping equipment, so any gain is a good gain. I'd be happy with 5%

...and based on our experiences with in-and-around-town driving, you may be much closer to reality than many of us might otherwise guess. After all, you're gonna be starting off in a considerably (& possibly not necessary) lower 1st gear. Also, you may find the need to get to a faster speed before getting into 3rd, or the 1:1 gear!

[61K10]

I ran a 700r with 3.08 gears(killer on the freeway) with a tci non lock-up converter which acts just like a regular conv. (trans has to be modded for a non lock up) ran a 2004r also. both of these trans have a much lower !st gear

[kieth]

One cannot make universal statements about how a transmission will perform with a 700r4 without taking into consideration a lot of variables. Here is a list of those variables:

1. engine HP and torque curve,

1a. torque at clutch engagement

2. transmission ratios

3. rear axle ratio

4. Tire size

I currently have a 200 hp 350 tbi engine out of a 91 burb, 3:73 gears, 700r4, 265-70r 17 tires (30" diameter). This combo works fine, since the tall rubber , light weight of my truck, and overall ratio I cruise at 70 mph at 2000 rpm approx. But this is not a barn burner, If I went to lower series tires the torque would increase but so would my rpms at cruising speed. I was looking for normal use, cruising down the expressway, and fuel mileage, so this set up works for me. One has to take all this into account before jumping off into the overdrive world.

i.e. 3:07 gears with tall tires and a 700r4 could only be run if you have a stump pulling big block since it has lots of torque, when the transmission goes into the overdrive gear it actually gives up torque for reduced rpms
(400 ft lbs X .75 = 300ft lbs at the tailshaft of the transmission) IF one is running 24" wheels it may reduce the overall ratio so much that the truck will be sluggish with only a small hp 230 engine , the truck would not get out of its own way and would have to be downshifted to go up a hill (lugging the engine)

HP=RPM X TORQUE / 5252

OR CONVERSELY HP X 5252 / RPM = TORQUE

MY TRUCK AS AN EXAMPLE 200 HP@ 4000RPM

200 X 5252 / 4000= 262.6 FT LBS OF TORQUE

NOW WE LOOK AT HOW MUCH TORQUE IS AVAILABLE AT THE TAIL SHAFT OF THE TRANSMISSION

TORQUE X RATIO= TORQUE AVAILABLE AT TAILSHAFT IN ANY GIVEN GEAR


700R4 350 400
1ST GEAR: 3.06 2.25 2.48

2ND GEAR: 1.62 1.52 1.48

3RD GEAR: 1.00 1.00 1.00

OD RATIO: .70 (30% INCR IN SPEED W 30% REDUCTION IN TORQUE)

263 FT/LBS X .70 = 184.1 FT LBS X 3.73 (REAR RATIO)= 686.69FT LBS / 2.5=275FT LBS OF TORQUE TO THE GROUND.

=392 FT LBS IN 3RD GEAR

=636 FT LBS IN 2ND GEAR

=1201 FT LBS IN 1ST GEAR

THIS REALLY ONLY TAKES ON MEANING WHEN YOU COMPARE IT TO SOMETHING THAT YOU ALREADY KNOW HOW IT WORKS.

HERE IS ANOTHER EXAMPLE:

250 6 CYLINDER 3 SPEED ON TREE OR 350/400 AUTOMATIC 3:73 26" TIRE DIAMETER

160HP X 5252 / 3500RPM = 240.10 FT LBS OF TORQUE

240. X 1 X 3.73 =895.54 FT LBS / 2.25" = 398FT LBS OF TORQUE TO GROUND
other engine, trans, wheel diameters, rear ratios will perform differently

240 X .70 X 3.73 / 2.25 =278.5 FT LBS OF TORQUE TO THE GROUND WITH A 700 R4
350 OD
3SPD 700R4

160HP 6 398 278 TORQUE TO THE GROUND

2OOHP 350 392 275 TORQUE TO THE GROUND


THE BIG DIFFERENCE HERE IS SMALLER TIRES ON THE 6 CYLINDER, HENCE THE TORQUE TO THE GROUND IS ABOUT THE SAME.....AND THE 6 CYLINDER OPERATES AT A LOWER RPM HENCE THE HIGHER TORQUE NUMBER.

THE OTHER FACTOR IS AT WHAT RPM IS THE ENGINE OPERATING AND AT WHAT SPEED IS THE TRUCK TRAVELING. I AM BUILDING A CALCULATOR FOR ANALYZING TORQUE WITHIN A USABLE RANGE OF SPEED SO IT CAN BE USED AS A EVALUATION TOOL FOR ALL COMBINATIONS.

[greenmtnboy]

Originally Posted by 64fleetside

A 350/700r4 with a 3.07 rear will lug that engine pretty badly, will likely give less MPG. It will work, but seem doggy. 3.42 is about the limit when using an OD trans. You will also find accelerated flat-tappet cam wear at low cruise RPMs-the engine does not run fast enough to lube the cam well enough.

I disagree with BOTH statements. My 1994 Roadmaster wagon came stock with 2.93 and a 4L60E as I'm sure lots of factory apps came with numerically low gears and OD. and premature cam wear? Really? I've never heard of a cam wearing out from too much idling.
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[luvbowties]

Originally Posted by greenmtnboy

I disagree with BOTH statements. My 1994 Roadmaster wagon came stock with 2.93 and a 4L60E as I'm sure lots of factory apps came with numerically low gears and OD. and premature cam wear? Really? I've never heard of a cam wearing out from too much idling.
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I too have noticed many of the factory cars using these overdrives in cars along with numerically low ratio differentials--Impala SS's, Caprices, Camaros, Fleetwoods, 'vettes. But, along with such ap's, I also notice they all seem to have either an "LT-" or an "LS-type" engine--engines that produce a LOT of low-rpm torque.

I've also noticed that with older type carbureted engines(which lack the "LX's" low-rpm torque), the overdrives do indeed tend to lug if paired with too "low" a differential. We transplanted a '93 Roadmaster engine with a TBI 350 engine that had a 3.73 differential (factory, we assumed, as we removed the power train ourselves from the entire car we had bought) both into a 1968 C10. The pickup originally had like a 3.36 differential in it that pulled OK with its stock 350 engine and TH350.

After the swap, we noticed the pickup pulled & shifted fine--in the 1st 3 gears--as compared to the carb'd 350 and TH350. The owner had hoped for much better gas mileage--gaining overdrive AND fuel injection. His experience was a barely noticeable improvement in gas mileage. Plus, in overdrive, it would barely pull a low hill while in the 40-55 mph range; it would shift back into 3rd gear with the slightest requirement of more accelerator, if in that speed range. We had even hooked up his brake light switch and vacuum controls and cruise control from/to the stock-and-unaltered computer--everything from the '93 Roadmaster, including all the R/M wiring. His kick down, up shifts, and down shifts all felt relatively fine and normal, with the exception of the 3-4 shift; we never got this one to shift really firmly, just okay; plus the shift into convertor lockup was really just a tad better than noticeable, maybe tolerable?


Initially, the 700R4 wound up too tight/fast before it would shift into 2nd, kinda like 18-20 mph, and would head-bang when doing so--all the time barely feathering the take off. Playing with governor weights and mostly the springs (from B&M's kit), we finally got it to shift into 2nd at 15 mph--and then only when accelerating like may be expected from an 85-year-old--w/o slipping or head-banging.


The owner's driving consisted mostly of under 55, very little I'state driving, and lots of in and around town in the 45 and under speeds. He later found a complete 3.08 posi that he wanted installed, thinking lower final drive numbers meant better gas mileage. We did this swap, only after we advised him that his "number" was already quite "low"; and we advised him to find a 3.73 posi(Remember: this eng-trans-combo initally came using a 3.73.) which we theorized would be a better fit--but he was a carpenter, not a car man, and he was the one paying! With the 3.08 not only did his mileage drop, but he and his truck were both unhappy in all gears except 1st, which I admit really felt better than with the 3.36. Now, 1-2 would not occur until about 22, but sounded and felt more natural; yet, other shifts were proportionally higher while feeling more like it'd be at home in a desert setting with higher speed limits and with lots of straight, law-deserted highways.

Last we heard was that he traded it in on a newer F***. I would've jumped at a chance to buy the '68--would've made a fantastic rat rod and with a proper differential should have been a fun driver; or, add a nice seat to replace the Indian blanket throw-type, carpet, and only minor body repair before paint, would've been a nice enough long bed driver for Sunday church!

Now to low-rpm and/or excessive idling causing premature cam wear: I'm basing these statements on personal experience with about 13-15 short bed Chev pickups--one 1967 or '68 and remainders 1971-1972 models, mostly, if not all with 350 engines. I was a dealer, who lived in a small town whose garbage pickup was done using these C10's that each pulled 2(maybe sometimes even 3) trailers slowly along the streets. They seldom exceeded 15, maybe 20 mph; and they did lots of starting/stopping with boo-koos of idling and low-rpm pulling. When the city decided to sell these pickups, along about 1976-77, many of us knew the mileages were really quite low, kind of like in the 25-45K range. Our vehicle maintenance manager, whom I had gotten to know quite well over the years, came to the city job from where he had been head mechanic & service manager of the local Chevrolet-dealership (Incidentally, this was the very 1st dealership the now-famous Nascar owner, Rick Hendrix, ever owned!). This service manager with all his years experience really qualified him well for this city-job--jmho, but shared by many!

He told me, when I specifically asked, that the only problem he knew the soon to be auctioned trucks(all to be sold "as is")had was many probably would need new camshafts. My curiosity was aroused. He explained, his words, that the low-speed pulling along with prolonged idling resulted in less-than-needed "oil splashing" of the cams as well as less-than-adequate oil pressure protection against both lube AND heat problems on the lobes AND lifter bottoms. Even told me he had replaced most of the cams once already--some quite recently, some awhile back--but answers quickly became short when I asked which ones were recent; I respected his reluctance to furnish 'inside information' altho' I'd have been more than happy to hear and make notes of his wealth of info. Last advice he would give was for me to just assume they all needed new cams, as I was bidding, and that would keep me safe!

I ended up buying 4 of them. Sold the '67 or '68(?) to the then-present service manager at the Chev dealership--he knew the truck better than I--for a happy but reasonable profit. Said he already knew he was gonna have to replace the cam--which he immediately did, as he installed a non stock with a nice little lope to it. The other 3 I sold quite soon, after cleaning/re-painting/seat-rebuilding, all of them. Advertised them as being the "ex-city trucks that I had been told needed cam & lifter replacement, altho' my mechanic and I could not tell by their performance that any of them needed such repair". Best I ever learned, only 1 of these 3 purchasers actually replaced a cam, and this one after nearly a year of everyday driving.

My end feelings for daily driving, are that in our resto-mods using od trannies with carbs, we need to remain with the (using round numbers) 3.50-4.00 ratio differentials. The 700R4 has an od ratio of .70, yielding a final drive, with above diff'ls: 3.50 X .70 = 2.45; and 4.00 X .70 = 2.80.

[[***Remember back in the 50's through 60's, GM had an overdrive using the 3 speed on the column with the pull-out lever to lock those od trannies into regular 3 speeds? They came with 4.11 differentials. Those overdrives were also 70% gear reductions. With the 4.11, that yielded 4.11 X .70 = 2.88 final drive to the rear wheels. You could even use, comfortably, a 4.56 which ended up with a 4.56 X .70 = 3.19. If you could get those trannies to stay together, you had the best of both worlds--a nice 327 with the 4.11 would outrun many street cars in the 1/4 mile; then into overdrive with its 2.88 would outrun on top end that same streetcar you just out-dragged!!! ###Ever try to swap that 4.11 to a 3.55? Gave a really DEAD ratio of 2.49 (3.55 X .70 = 2.49)! @@@Even using a regular 3.36 with a 4-speed Muncie gave a dead accelerator--the 3.36 worked much better with a factory 3-speed than with the longer-legged 1st gear offered by the 4-speed.]]

If we go to tbi, we may get away with 3.25-4.00: 3.25 X .70 = 2.28; and 4.00 X .70 = 2.80.

And if we go to multi-port injection, we may get away with 2.75-4.00: 2.75 X .70 = 1.93; and 4.00 X .70 = 2.80.

All the above just my opinions; however based on real-world "feel" and some actual experience of different applications. The 'law of diminishing marginal returns' applies to smaller numerical final drives delivering better gas mileage just like it applies to {about} everything I've ever experienced: too much of {about} any good thing eventually becomes "less good" as we increase it beyond a point. Also, the amount of improvement--or even negative improvement--so much depends on where we are starting from: gear ratios and acceleration and fuel mileage and wear included.

Not sorry for the long-winded remarks, as my wife is away on vacation to a far-away island state. And this gave me a much-needed outlet as I have no one to talk to--or talk "at"!

[64fleetside]

Your roadmaster has a roller cam, not a flat-tappet cam. The same cam wear at low speed is the same reason new flat-tappet cam break-in is so important.

[Chvy2NV]

A parts list would b e cool
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[shortbed70]

In my honest opinion because I ran my 700 for a total year now, granted my tire is only 26"tall a 3.55-3.73 would be ideal. Anything shorter gear wise an taller tire its going to lug the motor down and make the truck work harder to keep going. Just my opinion! I know my truck loves te 3.73/26"tire and 700! I can cruise 70-80 no problem not that I want to but I can!! Just saying. I think after all the pars I put in my trans I should've bought one but its got every bolt on possible externally. Set your pump pressure by the book also... If not they won't live, long!
Trans cooler, tv correction bracket of bowtie od kit, driveshaft, crossmember.
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