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Discussion Starter #1
Does anyone have any experience with the GEAR VENDORS
overdrive/underdrive unit. I am considering this unit, but it appears that you need to cut the drive shaft approx. 13 inches.
thats about half the shaft..... any comments on this...
 

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Hi Jeff,
I assume you are talking about a automatic? If not don't read any further :). My 700r4 came from bowtieoverdrives. The car doesn't run yet so I can't comment about the quality. For a 700 the crossmember needs to be changed (so I bought the bowtie tubular crossmember) and the driveshaft shortened, but 13" seems way off? I think it's about 2-3", someone else will chip in. I didn't change my original driveshaft but instead got a new one from Denny's driveshaft at the correct length.
A 200R4, from what I have read doesn't need shortening ?
Nick

 

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There's been some debate about that type of unit and I think when it comes to two wheel drive passenger cars it's a lot simpler and cheaper to just install a TH2004R or a TH700R4.

The gear vendor unit bolts to the back of a 3 speed automatic that has a removable tail shaft. It gives you different ratios above and below your gears. This is why it's valuable for a crawler or 4x4 of some kind.

They weigh a lot, add cost, and complicated shifting.

My opinion, get an OD automatic transmission.
 

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I put a 2004r in my 76. No change to the drive shaft and no change to the cross member. Got it from BowTie.
Would do it again....well worth the effort.
:thumbsup:
 

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thought on the 200r4 that the cross member needed to be modded ? ?
Im going today to pick up a 200r4 today.. its a core im going to have built out of a 87 grand national..
SO just want to confoirm.. sorry for the hijack..

I put a 2004r in my 76. No change to the drive shaft and no change to the cross member. Got it from BowTie.
Would do it again....well worth the effort.
:thumbsup:
 

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thought on the 200r4 that the cross member needed to be modded ? ?
Im going today to pick up a 200r4 today.. its a core im going to have built out of a 87 grand national..
SO just want to confoirm.. sorry for the hijack..

The cross member does not need to be modified.

However, you can bolt the cross member in backwards which points the tongue back. This will line it up with the TH2004R transmission mount.
 

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The cross member does not need to be modified.

However, you can bolt the cross member in backwards which points the tongue back. This will line it up with the TH2004R transmission mount.


LOL really that easy of a fix just turn it around.....sounds to easy.. and no corvette tax somethings wrong..LOL
:laughing::laughing:
 

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Discussion Starter #8
OVERDRIVE/UNDERDRIVE From "GEAR VENDORS"

Check out the GEAR VENDORS web
the pART in questions you simply attach it to the tail of your existing T400. remove the factory tail and attach their unit to the factory trans. this thing splits the geAR AND YOU END UP WITH A 6SPEED AUTO!!!!
sounds promising, big $$$ 2500.00
the problem here is the unit is approx. 13", meaning you need to cut the stock drive shaft approx. 13" leaving you with maybe 17" drive shaft.... THAT'S THE $64K. QUESTION.

check it out www.gearvendors.com. if the link doesn't work google them :surprised
 

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Hi mate, Over here (AUS) those overdrive units died out late 80s. they where big ,heavy,expencive,and overdrive trans was wishfull thinking for most people here. Most had to adapt a 5 speed manual out of something else or go o/drive behind an auto. With the advent of 4speed autos the o/drive died here.
My 79 vett has a 200r4 in it and its the best thing since sliced bread!:D It changes so smooth i dont know what gear im in most of the time! but i can flick a switch and lock up convertor in 2/3/4:thumbsup:got 3.55 gears and it ideal for cruising. Not good for big cams:down: Bolts in tho.
link to a short vid first part shows the revs at 80kmph(47mph)
 

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Check out some articles on drag week. I think a lot o those guys are using gear vendors on high HP cars. Not sure if they take them off to race or not.
 

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GV is a tough part

The GV overdrive behind the 400 turbo will take a lot more abuse than the 200R4 or the 700R4. If you are making serious power they should be considered.

As far as price, yes they are expensive. If you are making enough power to break a 4 sp OD transmission then that gets expensive too. Build a 200R4 or a 700R4 twice and you have the GV paid for. If you have a mild cruiser, the GV isn't the way to go. With a healthy street strip car, I would go with the GV.

I'm new to the 'Vette world so I may be missing something Since the differential is solidly mounted with the IRS what would be the problem with a super short driveshaft? On a solid rear axle that needs the range of motion I understand, but the 'Vette diff doesn't travel other than the minor movement caused by the rubber mounts.
 

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If you are making enough power to break a 4 sp OD transmission then that gets expensive too. Build a 200R4 or a 700R4 twice and you have the GV paid for. If you have a mild cruiser, the GV isn't the way to go. With a healthy street strip car, I would go with the GV.
This is what I am thinking......built 200R4s and 700R4s break easy when over 500hp, unless you want to pay the price of a GV to bullet-proof it....and even those break all the time. And a nice short dirve shaft.....should be a bonus rather than a concern.
 

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More on the GV

My last build was a '62 Chevy half ton PU. I had a Cummins 4BT in it which is a 4 cyl. It is like a Dodge PU first series Cummins but with 2 less cylinders. I had a slightly oversized turbocharger and slightly bigger injectors. It had the 475 turbo hydromatic which is a 400 with straight cut gears. That makes them a little stronger.
Gear Vendors does NOT recomend their overdrive for use behind this motor. The reasoning is there are some serious power pulses with the 4 cyl. The motor made a lot of torque. When a piston fired it hit hard. The next piston was a long time coming compared to a 8 cylinder. My motor liked 1900 to 2000 rpm cruising, but was pretty much all in and rolling smoke at 2600 rpm. The pulses made the planitary gear set chatter in the overdrive. The gearing constantly slammed back and forth causing premature gear failure. At least that is my take on their saying NO for that installation.
I always wanted another gear in that truck, but it never got it. Without the OD I had to gear the rear axle super high, which cost the truck acceleration from the line. The high gearing did probably save me a couple of broken axles though.

Tom
 
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