Solution to high RPMS?

[Chevyguy111786]

I just installed a 4.56 rear end from a 1 ton. and with my TH350, i can get up to about 45 or so and the rpms are really high. Is there something i can do to either let it wait a while before shifting into second and then third. I'm considering a 700r4 but don't want to shell out that kind of money right now. Any other solutions?

[tomsC10R]

The only other possibilities is to change the gears in the rearend or put some huge a$$ tires on it, that's change the final drive ratio too I would change the rear end gears -- put some 3.55's in there, that is if they're available for that rearend, that I'm not sure of.

Good luck,
Tom

[dinnut]

4.56 is pretty high. thats an acceleration/towing rear... maybe that wasnt a very good decision to install something that big

[72 Blazerman]

you might have to use a overdrive tranny. I had 4.88 gears in my chevelle and was taching 3 grand at 45 mph.

Doug

[Chevyguy111786]

dinnut...i know what the rear-end is for. Maybe it was a good idea because it's for use in a TOWING vehicle. I need the low-gears. was just curious as to whether or not there was a kit i could put in my transmission. I will end up getting an overdrive tranny, but was wondering about short term solutions. Thank you for your help.

[lukecp]

Bigger tires would help out a little bit...would shave off a couple hundred RPM.

[cableguy0]

anything your using for towing DO NOT use a 700r4 you will break em constantly and they arent cheap to rebuild as you already know.gear vendors makes and overdrive unit that bolts to the back of the transmission that actually works as a gear splitter too but i think it costs around 1500 bucks. but you can get the best of both worlds

[Longhorn Man]

And I have spoken to our local gear vendors sales rep through our shop. They have been selling them out of a local HD tranny place since they came out, and to date, have NEVER had one come back for mechanical problems. They have been installing them on school busses, RVs and even some straight trucks.
This is one tough auxullary tranny.
If you were to put a tack on your truck, you'll probably find that the RPMs are not as high as you think.

[dinnut]

oh... sorry. bigger tires

[Chevyguy111786]

I've got bigger tires on the way...and i think i'll go invest in a tach. What's an RPM range I should look out for bein too high. I just have a 350 with a th350. I'll be puttin a big black in over the summer i think.

[BLACK AND BLUE 67-72]

Yeah, the Gear Vendors overdrive is supposed to withstand 1,000 HP easily. So I would say that they are pretty tough! 3500 to 4000 RPMs would be a little excessive I think, mine runs 3000 RPMs at 60 with 3.73's and I would really like to have a Gear Vendors unit hooked to my truck.

[Clancy68]

Don't be so quick to shoot down the 700r4. theres a lot of missconception about "breakage" associated with the early models..
I currently am running one behind a 6.2 diesel with a banks turbo kit. in my 84 blazer and use it to tow my buddies camaro and trailer to the track, 2000 lb horse trailer with 2 fat nags in it, etc. it has a towing/heavy duty shift kit, some minor upgraded parts, (clutch packs, upgraded input shaft) th upgraded input shaft is standard on most of the later tranny's after 85. that motor is belting down over 400 ftlbs at 1800 rpm. (built up big block territory) you can easily build/buy one for a lot less than just the gear vendors unit,( easliy under $1000 for a bomb proof one, and around half that for a set up similar to mine, which is all you need to tow up to 6500-7000 lbs, and that ends up being a stronger tranny than a stock to mildly upgraded th-350...as far a street RPM's when towing i belive its a good idea to set it up were you are turning aroud 2300-2500 at 60, that ends up being nice, becuase it allows the motor to pump a little more coolant and oil, making it happier, the main thing you run into with spinning the motor too fast is effeciency, its becomes thirts, provided you have a good cooling system. but to be safe i would say try and keep it under 3000 @ 60mph

as far as a kit for the tranny you have, the kits that are avalible are usally to change the shifting charachteristics of your tranny, i havn't seen different final drive ratios, just first gear stuff for powerglides.

by the way I have not had a single my 700r4...i also love getting 21-25 mpg.



--Scott

[Fred T]

I know you just swapped rears, but I would suggest another swap. Go to a 14 bolt corporate rear from a late model. 3.73 gears are an easy score, some of the newer ones have 3.42s. Since you have a flatbed, width isn't that big of a factor, but you should be able to find one that's within an inch or two. Your only other economical swap is to find a 64-72 full floater with 4.10 gears, you can swap pumpkins. Aside from that, you can buy ring & pinion sets in 4.10 or 3.90 from Randy's Ring & Pinion, but you're talking serious money.

The 700r4, properly equipped, will handle fairly heavy loads. But the newer 4L80E is far better.

[kiley]

Randy's doesn't sell 3.90's anymore. Tried to get some a couple of months ago.

[72 CustomCamper]

Originally posted by Clancy68
Don't be so quick to shoot down the 700r4. theres a lot of missconception about "breakage" associated with the early models..

Hey Scott I agree with you. When my uncle still owned my truck it had a 6.2 diesel 700r4 combo from an 84 blazer. The truck more than once was used to tow a 6 TON dozer with no problems. Also has hauled over 6 TON of rocks in the bed more than once. Most people that bad mouth the 700r4's probably have never even had one...

Chuck

[ZOOMY]

I tow with a 700R4 all over the country. With an empty trailer I use overdrive, but when it's loaded I just put it in drive. If you tow heavy loads in OD the trans will upshift / downshift constantly & overheat, a tranny's worst enemy. Also use a trans cooler & in the summer I take off the flywheel cover to let air in to cool the converter.

[Fred T]

Originally posted by kiley
Randy's doesn't sell 3.90's anymore. Tried to get some a couple of months ago.

Art Houser has them, according to his website. Just don't believe everything he says. When he first started selling gears for the older 3/4 tons he led some people astray, hopefully he learned from his mistakes. http://www.rearman.com/truck.htm

[Chevyguy111786]

Clancey:
How much would a tranny setup like you have cost me?

[Clancy68]

get your hands on a good core try and find a later one if you can, so you don't need to plunk down for anymore hard parts than you have to. then depending on your time/money/mechanical ability, either go to an aftermarket website, summit, jegs, scoggin etc. and get a "heavy duty" transmisson rebuild kit... which go for around $200
or take the core down to a local trnsmission shop tell them what you want to do(heavy duty parts, so you can tow easily) and they will have it ready for you in about a week for between ive heard as little as $400, depending on how well you know the guy, and more like between $500-600...and also as zoomy said, a transmisson cooler is well worth the investment, also a transmission temp guage is never a bad idea when towing.
let me know if you have any more questions
--Scott

[Chevyguy111786]

I'll get out this weekend to some junkyards and try and track down a core. What year's and cars/trucks should i look for? what's a good price to pay for a rebuildable core, but one that might not work right now? I once had a guy tell me it'd be 900 to get my th350 rebuilt, i told him i could get a new one for that. Then someone told me they could get it done for 350 bucks. But when i started lookin into my tranny farther, I changed the fluid and the filter wasn't bolted on..it was laying in the pan, Replaced it and it seems fine now. just want the benifits of overdrive. Thanks for all your help.

[Clancy68]

i think anything after 1985 has the better hardparts in it., i don't know as far as good cars or trucks to pull them from, got a few vouches for blazers here, light trucks, camaro's are two that pop into my head. they are pretty common, someone here might know good vechicles to pull from.

if you can get the pan off then and there, try and look for signs of a bad core in th pan, lots of metal chips and flakes a little is normal, dark fluid with a burned smell.
a similar trans that you want to stay away from is a 200 R4, identified by a coner notch in the pan, and says METRIC. those can be made good, but for lots of money, kinda like powerglides.

as far as a good core price, your gonna have to shop around, you might want to do some online searches for some rebuilt ones, and see what the core fee is, as intuition will tell you a good price will be less than that, becuase half the purpose of thier price is to keep them comming in to rebuild them.

--Scott

[73stepside]

the better 700's are 88-up. you can get any 700 and have the upgrade components installed. the 700's came in all fullsize trucks and cars. stay away from anything under 4.3 v6 they are a smaller bolt patterna and won't fit but the torque converters are rated about 2000 rpm so there is a good trade off.

[Longhorn Man]

You sure about that 73? The 4.3 has the exact same bellhousing as the V-8. As does the 2.5 4 cylinder.
The 2.8 is not the same thoguh.
I would stay away from camaro units though, they are mounted at an angle.

[73stepside]

2.8. 3.4 and 3.8 all have smaller bellhousings but the torque converters are the same. 2.5 4 i didn't know about the size of bellhousing. the 4 cylender fbodies used a 200 metric 3 speed auto. i know that the 4.3 is the exact same that why i said anything under 4.3. the fbodies are mounted the same, they just have the extra material on the tailhousing to mount a torque arm from the rear axle housing

[smokekiki]

Depending on your application,Gear vendor units are between $2200-$2800.Plus the cost of driveshaft work.Would love to have one!Send Your donations to.......