Hello,

I am looking to either install a used gear vendors unit or perhaps change the gearing from 3.55 to 2.73 or 3.08. What effect would this have on performance and gas mileage? Someone told me I would need to keep the 3.55 due to the cam? Here's what I got...

A freshly rebuilt 454 4 bolt, cast crank, .30 over, peanut port 045 heads (heads flowed 264cfm, they have 230cc intakes - but are still peanut ports) with 2.06 in and 1.88 ex, 8.75 comp and a XE274 cam with 1.8 rockers and necessary springs. It has a performer intake with an edelbrock 750cfm carb. The computer dyno said 398 hp at 4500rpm and 560 tq at 2000rpm. And that's it out of breath by or close to 5,000rpm. TH400 with a trans go shift kit and a hughes 2,300 - 2,500 stall. The rear is a posi 3.55 8.5 ten bolt. (It's a 68)

Thank you for your time...

The dyno numbers sound a little out of whack. The definition of horse power is Torque equals Horsepower at 5252 RPM. Also, a dyno that reads starting at 2000 rpm has yet to be invented. 2500 is the starting average.
Also you left out a vital factor. How much do you want to spend???
A GV OD will have to stay in OD for a long time to pay for itself. But there are plenty of other benny's like reduced engine speed and better cruisability (is that a word?), longer drive train life too because of the lower speed of everything from the fan to the rear of the trany. And, of course, it'll turn your TH400 into a four speed. Gearvendors claims it would turn into a 6 speed via splitting gears, but I never figured out how to do that.

Thank you, Fred.
I agree. The dyno numbers sounded way off. It was a computer dyno sim 3 and I noticed he entered the heads as open chambered when they are clearly not. (I misplaced the document) What can I expect when I fire up the motor?
What kind of performance difference will the 2.73 vs 3.08 vs 3.55 gears make? I'll be on the freeway for no more than 5-10 miles at a time a couple of times a week, then short hops and street driving. (It will be a daily driver.) I plan to make a couple of 800 mile roundtrips a year, depending on how I sort this out. It will see the drag strip about twice a year, if that. What kind of e.t. differences with those gears? Thank you for your time.

I had 3.08 in a chevelle and went to 3.73. I noticed a better take off from start and it still was good on the high way with a turbo 400. (Just trying to give you an idea?) Did you try a drive line sight that calibrates your rpm? Look on tremics sight they sell autos as well as standard trans.(Just another Idea)

Thank you, Fred.
I agree. The dyno numbers sounded way off. It was a computer dyno sim 3 and I noticed he entered the heads as open chambered when they are clearly not. (I misplaced the document) What can I expect when I fire up the motor?
What kind of performance difference will the 2.73 vs 3.08 vs 3.55 gears make? I'll be on the freeway for no more than 5-10 miles at a time a couple of times a week, then short hops and street driving. (It will be a daily driver.) I plan to make a couple of 800 mile roundtrips a year, depending on how I sort this out. It will see the drag strip about twice a year, if that. What kind of e.t. differences with those gears? Thank you for your time.
Michael,
That drag racing difference is not a matter of those gears. It's practice, practice, pr,,, you know.

And a mid 3-set of gear sounds like the sweet spot for you. Well, they're great for most of us.
And thanks for my time? You're welcome, but that's what we get paid to do.

Michael,
And a mid 3-set of gear sounds like the sweet spot for you. Well,


X2 :yes:

2.73 = about 2000rpm at cruise
3.55 = about 2500rpm at cruise
3.73 = about 2800rpm at cruise

Cruise speed of approx 60mph and 28" tall tires.

Stick a taller tire on for daily driving and a short slick on for track days ???? Just an idea and a best of both worlds try at things :)

I have 3.08s and love them.

try the link below it is to American Power Train and they have a speed analyzer

http://www.americanpowertrain.com/tools/GM/ap-gm_analyzer_5sp.html

Michael,
... but that's what we get paid to do.

Who's "we" ... l:)

Thanks for the input, fellas ...

Who's "we" ... l:)
Oh No John! That's how I pay for my car!:disco:

...That's how I pay for my car!:disco:

And to think - I never even got my "Free" stickers ... :sad:

And to think - I never even got my "Free" stickers ... :sad:
You can have some of mine.:yes: They sent lots. Do you want big or small?:D

Pssst, I was kidding about,,,,, never mind. You knew that.:beers:

Keep the 3.55's and add a beefed up 700R4 that is rated for 550 hp. I did with my 3.90 gear and 3200 stall, hydraulic lockup.. I run 2600 rpm at about 70 mph now... I had a TH 400 with a 3500 stall and was running 3800 rpm at 70 mph. I can give you the place where I bought it from... I can tell you it will be around $1000 with stall converter minus shipping... i think it cost me $200-250 for shipping... Shifts very nice and crisp. I have 1500 miles or so on mine with no problems. Low 1st gear you will like too...

in order to get a little more rpm out of your engine, the peanut port heads are holding you back big time. Get a good set of 781's or 049's with 2.19/1.88 valves and will flow much better.. That is what I have with a roller 468 and they work awesome! Of course there are better heads out there, but if you are on a budget, they work great for much less $$$$...

I agree with Geremy. The 700/r4 with mid 3 gear is a great street combo.Did it on my 67 pickup with a 408 with approximatly 450 horsepower 4yrs ago and love it.My newer tranny doesn't shift as hard as the th400 I had before but not bad.But it is a dream everywhere except if you spend alot of time at the strip.I've put over 12000 miles on this combo so far .No problems at all.I will go the OD route again on my 69 Camaro for sure.

I picked up a used GV overdrive and love it. Running 3.50 gears as well. I had a 700r4 in my last car and my dad's as well. Never did like it or the way it shifted. Plus if you hurt one it costs alot more to fix.

Keep the 3.55's and add a beefed up 700R4 that is rated for 550 hp. I did with my 3.90 gear and 3200 stall, hydraulic lockup.. I run 2600 rpm at about 70 mph now... I had a TH 400 with a 3500 stall and was running 3800 rpm at 70 mph. I can give you the place where I bought it from... I can tell you it will be around $1000 with stall converter minus shipping... i think it cost me $200-250 for shipping... Shifts very nice and crisp. I have 1500 miles or so on mine with no problems. Low 1st gear you will like too...

in order to get a little more rpm out of your engine, the peanut port heads are holding you back big time. Get a good set of 781's or 049's with 2.19/1.88 valves and will flow much better.. That is what I have with a roller 468 and they work awesome! Of course there are better heads out there, but if you are on a budget, they work great for much less $$$$...Im allways amazed how two people can have completely different ideas on how a drive line should be done, I think the gear vendors with the turbo is a good idea, I would get rid of the hughes converter and get a good unit. Personally I like the peanut ports, and the results they deliver. Does a kick down cable ever really belong on a muscle car? Im allways curious as to how the 700R4 cars run at the track, I didnt notice any times posted with your car, please feel free to elaborate.

I picked up a used GV overdrive and love it. Running 3.50 gears as well. I had a 700r4 in my last car and my dad's as well. Never did like it or the way it shifted. Plus if you hurt one it costs alot more to fix.Agreed, And... a peanut port big block done right WILL hurt it.

Not sure why everyone is down on the 700R4... i know if you build them right, they are awesome, but stock they suck.. Mine shifts hard into 2nd...extremely quick shift... it has no electronics, all hydraulic. I love it.. they are more expensive than a 350 or 400, but it will get your rpms where you want to, and try finding a used GV overdrive is not easy! Love the low 1st gear, especially with my 3.90's and roller big block... Fun, Fun...

Im allways amazed how two people can have completely different ideas on how a drive line should be done, I think the gear vendors with the turbo is a good idea, I would get rid of the hughes converter and get a good unit. Personally I like the peanut ports, and the results they deliver. Does a kick down cable ever really belong on a muscle car? Im allways curious as to how the 700R4 cars run at the track, I didnt notice any times posted with your car, please feel free to elaborate.

Mark... I don't have any times yet... I haven't been to the track yet. I hope to get there this year... I have a set of wrinkle wall slicks that I am dying to test out.

I looked for a GV unit, couldn't find one anywhere... It wouldn't have mattered anyway... my 400 was too far gone... My 700R4 is rated for 550 hp... Don't know if it will hold that, but all the weak internals, IE... sun shell, valve body, sprag, have all been swapped for heavy duty parts... I built my car to drive and have fun. Hell... I run it on pump gas! ;) I don't race every weekend, so I hope it holds up well... There is another member on here than runs a 700R4 with a 496 in a 68 that loves it as well.. My buddy had one in a 55 Chevy Pro Street with a blown 454 and it held up nice as well. Never ran it at the track either...

Mark... I don't have any times yet... I haven't been to the track yet. I hope to get there this year... I have a set of wrinkle wall slicks that I am dying to test out.

I looked for a GV unit, couldn't find one anywhere... It wouldn't have mattered anyway... my 400 was too far gone... My 700R4 is rated for 550 hp... Don't know if it will hold that, but all the weak internals, IE... sun shell, valve body, sprag, have all been swapped for heavy duty parts... I built my car to drive and have fun. Hell... I run it on pump gas! ;) I don't race every weekend, so I hope it holds up well... There is another member on here than runs a 700R4 with a 496 in a 68 that loves it as well.. My buddy had one in a 55 Chevy Pro Street with a blown 454 and it held up nice as well. Never ran it at the track either...Thanks, my problem with the 700 is the low first gear which does not let the converter multiply torque, then theres the kick down cable which usaually causes the carb not to go full throttle, I guess Im just a turbo guy.

Thanks, my problem with the 700 is the low first gear which does not let the converter multiply torque, then theres the kick down cable which usaually causes the carb not to go full throttle, I guess Im just a turbo guy.

I had to grind down the tv cable bracket just a hair to make it not rub, and then had to adjust throttle rod just a hair to get WOT.. I have a loose converter at 3200 rpm, but it's tighter than you think and 1st gear all the way through... this thing comes unglued! :cool:

Not sure why everyone is down on the 700R4... i know if you build them right, they are awesome, but stock they suck.. Mine shifts hard into 2nd...extremely quick shift... it has no electronics, all hydraulic. I love it.. they are more expensive than a 350 or 400, but it will get your rpms where you want to, and try finding a used GV overdrive is not easy! Love the low 1st gear, especially with my 3.90's and roller big block... Fun, Fun...When you make it to a drag strip, It will be easy for me to explain to you why I dont like the 700 R4, again, does a kick down cable really belong on a muscle car? For a street rodder with a ZZ4 they are fine, for a 9 or 10 sec street car no way.

Man, I wish somebody could tell me where to find a used GV unit. I've thought about finding a RV graveyard but not easy to find. Any ideas where they can be found?

Chet, maybe Gear Vendors has a trade-in at a good price. You might get my old one. It was like new. Why did I trade it in? Hell if I know.

I found mine on a 4x4 website. Also check craigslist and ebay as well.

Man, I wish somebody could tell me where to find a used GV unit. I've thought about finding a RV graveyard but not easy to find. Any ideas where they can be found?


I'll PM you a link to one. I was debating on buying it for my other car, but can't swing it right now. It's brand new and for a th400.

gear vendors does do well as an overdrive but at a huge cost to HP and torque!!!!!
in other words they are horsepower leeches!

When you make it to a drag strip, It will be easy for me to explain to you why I dont like the 700 R4, again, does a kick down cable really belong on a muscle car? For a street rodder with a ZZ4 they are fine, for a 9 or 10 sec street car no way.

1st. 700R4s do not have Kick down cables. The tranny runs with a TV cable and when adjusted correctly they are great trannys.

Do 350s or 400s belongs on the track???

Ask the Glide guys and see what they say.

We put one on my buddies camaro. I would love to put one on my camaro. I have a buddy that is a dealer for gear vendors.

And yes Fred they can be a 6 speed. Just depends on how you shift the trans and hit the dimmer switch.

Trans in 1st gear- 1st gear
Run rpm up in 1st , hit dimmer switch- 2nd gear ( dont shift ) first gear overdrive
Shift in 2nd and hit dimmer switch- 3rd gear ( normal second gear )
Run rpm up in 2nd ,hit dimmer switch- 4th gear ( dont shift ) second gear overdrive
Shift in 3rd and hit dimmer switch- 5th gear ( normal third gear )
Run rpm up in 3rd, hit dimmer switch- 6th gear ( dont shift ) third gear overdrive

This whole time you are shifting the trans and punching the dimmer switch on the GV.

Seems like a lot of work.

Or just put the trans in Drive and get on the highway and push the dimmer switch to go into overdrive and act like it is a four speed trans.

You don't even have to hit the switch for OD on the highway. Just put the unit in Auto and it will kick in the OD automatically at I think it's 52 mph.

I've been looking at a GV overdrive. I also think that's the way to go. Rule of thumb is that 700R4 "should" be good up to 500hp, after that you're on borrowed time. TV cable is major PITA, and I don't care what they say or what TV system they use. Get it slightly wrong, and you toast the tranny. Also, fact is that the same guy/shop that will build you a 600hp 700r4 will also build you a 900hp TH400. There is a reason for that. The funny story is that when I called Mark about hooking up the kick down cable on the TH400 for passing gear functionality he told me "...don't bother, you will not be needing a passing gear...". I quickly realized what he meant by that and never did bother with it.

I have read on this site that the GV overdrive unit hits the floor in certain applications.

I read that too and that some minimal tunnel reshaping may be needed. Some hammer work on the tunnel does the trick.

Matt, your guy must have been talking about the kick down cable for a tranny other than a TH400. Those don't have one. They're electric.

We put one on my buddies camaro. I would love to put one on my camaro. I have a buddy that is a dealer for gear vendors.

And yes Fred they can be a 6 speed. Just depends on how you shift the trans and hit the dimmer switch.

Trans in 1st gear- 1st gear
Run rpm up in 1st , hit dimmer switch- 2nd gear ( dont shift ) first gear overdrive
Shift in 2nd and hit dimmer switch- 3rd gear ( normal second gear )
Run rpm up in 2nd ,hit dimmer switch- 4th gear ( dont shift ) second gear overdrive
Shift in 3rd and hit dimmer switch- 5th gear ( normal third gear )
Run rpm up in 3rd, hit dimmer switch- 6th gear ( dont shift ) third gear overdrive

This whole time you are shifting the trans and punching the dimmer switch on the GV.

Seems like a lot of work.

Or just put the trans in Drive and get on the highway and push the dimmer switch to go into overdrive and act like it is a four speed trans.
Mike, how would anyone do that with an L88 at full throttle? Cruise mode, yeah. But why?

Matt, your guy must have been talking about the kick down cable for a tranny other than a TH400. Those don't have one. They're electric.
Correct, th350 kick down cable, th400 kick down "wire" , Marks point was "none needed" ...

Mike, how would anyone do that with an L88 at full throttle? Cruise mode, yeah. But why?

Fred, you just need to drive that sucker. lol

It does seem complicated but when I rode in my buddies car and he did it I was impressed. He has a 68 camaro with a pretty hot 502 aluminum head motor. But he is a dealer and has had it in the car for a while. He knows how to shift it and work the dimmer switch.

Fred, you just need to drive that sucker. lol

It does seem complicated but when I rode in my buddies car and he did it I was impressed. He has a 68 camaro with a pretty hot 502 aluminum head motor. But he is a dealer and has had it in the car for a while. He knows how to shift it and work the dimmer switch.
I wish I was that good.:yes:

1st. 700R4s do not have Kick down cables. The tranny runs with a TV cable and when adjusted correctly they are great trannys.

Do 350s or 400s belongs on the track???

Ask the Glide guys and see what they say.Hey expert how many guys on here have 700 R4s in 9 and 10 second full weight cars? Id be more than happy to supply you with a list of my customers with turbo 400s in full weight cars that run 9s and 10s. Its allways the guys who stay far away from the drag strip that praise the 700R4s, EVERY customer that has ever put one in front of one of my big blocks (700 R4) has hurt it, EVERY ONE, EVERY TIME. Thanks for correcting me on the TV cable, accuracy is important.
,

no tunnel work required. bolts in easily in our cars.

no tunnel work required. bolts in easily in our cars.

x2

I know on 70-73 Camaros you have to do a little "work" on the tunnel, but that's because those cars have very small tunnels at the rear of the transmission.

I have a GV unit , I purchased it so I can run 4.10's in the rear and still be able to drive it on highway cruises comfortably ---

Regarding strength, I have read that these units will withstand up 1000hp. I was wondering if anyone here was running one of these units behind +500hp? Any issues?

Regarding strength, I have read that these units will withstand up 1000hp. I was wondering if anyone here was running one of these units behind +500hp? Any issues?

I have a friend who has a 55 prostreet car. 502 w/6-71 blower. He has driven the car from Texas to California and back. He also takes the car to the track and races it. He has been in magazines and on television. I believe is was Hot Rod Power and his name is Sonny Poteet. Drives his car everywhere.

So yes it will handle horsepower, I thought it was 1200 hp.

Do a google search on him.

http://www.google.com/search?hl=en&safe=active&q=sonny+poteet&btnG=Search&aq=f&aqi=g-v2&aql=&oq=&gs_rfai=

http://dallasclassicchevy.com/FeatureCar0508Poteet.htm

Yes, they will take 1200HP in stock form and can be modified to handle even more power. The only draw back to a Gear Vendor is the price, they are not cheap, but they are made well and last forever.

It's a simple and strong planetary unit so I have no problem believing their ratings.
Think of how strong a PowerGlide is when built - they are based on simular concepts.

I only know of one application of +/-800Hp with one and it lives reliably on the street and track - not one problem with the GV unit in 4+ years.

I belive they supplied Troy Trepanier with a unit for his Land Speed Record "BlowFish" in the last couple years - isn't it rated at over 2000Hp :eek:

(edit: Dang Royce types faster ...)