Sad Story On a Gear Vendors OD

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TrailBeast

TrailBeast

AKA Mopars4us on Youtube
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A local buddy came up with a used GV overdrive for his 71 Swinger and I offered to help him with it since he had never done much of anything gear train wise before.
We split the hump under the drivers seat and welded in a section to make a taller hump to clear the overdrive unit, re designed his exhaust pipes to go around it by taking a section out of both pipes behind his crossover and adding them in the front to move the crossover behind the OD unit.
We shortened a spare driveline to fit the new longer unit, and moved all his good U joints to the shortened driveline.
Got it all installed, filled with fluid, wired up and.....It didn't work.:(

We could hear the solenoid activating but overdrive wasn't there.
Come to find out it was a destroyed unit with metal slivers in the screen filter.:BangHead:

Well, for 800 bucks Gear Vendors apparently will take a bad unit and rebuild or replace it, so this is what he is going to do.
I tried to talk him into doing a 42RH OD swap because we could do it for around 400 bucks total and that includes the shift kit for it, but no go.:D
He has a mildly hopped up 318 so the 42RH would be the ticket in my opinion.
He wants that GV unit.

The GV unit came out of a stockish van and shouldn't have been trashed by too much power, so we figure it must have been abused in some other way.

Bummer.
 
TrailBeast said:
A local buddy came up with a used GV overdrive for his 71 Swinger and I offered to help him with it since he had never done much of anything gear train wise before.
We split the hump under the drivers seat and welded in a section to make a taller hump to clear the overdrive unit, re designed his exhaust pipes to go around it by taking a section out of both pipes behind his crossover and adding them in the front to move the crossover behind the OD unit.
We shortened a spare driveline to fit the new longer unit, and moved all his good U joints to the shortened driveline.
Got it all installed, filled with fluid, wired up and.....It didn't work.:(

We could hear the solenoid activating but overdrive wasn't there.
Come to find out it was a destroyed unit with metal slivers in the screen filter.:BangHead:

Well, for 800 bucks Gear Vendors apparently will take a bad unit and rebuild or replace it, so this is what he is going to do.
I tried to talk him into doing a 42RH OD swap because we could do it for around 400 bucks total and that includes the shift kit for it, but no go.:D
He has a mildly hopped up 318 so the 42RH would be the ticket in my opinion.
He wants that GV unit.

The GV unit came out of a stockish van and shouldn't have been trashed by too much power, so we figure it must have been abused in some other way.

Bummer.
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That just bites. A lot of work to get to that point.
 
I might just bite the bullet and have Gear Vendor re-build. That puts them on the hook for at least some initial functional responsibility. Modifications were done to accommodate? I know it adds more wait time. Something that can be equally tough.
 
TrailBeast said:
A local buddy came up with a used GV overdrive for his 71 Swinger and I offered to help him with it since he had never done much of anything gear train wise before.
We split the hump under the drivers seat and welded in a section to make a taller hump to clear the overdrive unit, re designed his exhaust pipes to go around it by taking a section out of both pipes behind his crossover and adding them in the front to move the crossover behind the OD unit.
We shortened a spare driveline to fit the new longer unit, and moved all his good U joints to the shortened driveline.
Got it all installed, filled with fluid, wired up and.....It didn't work.:(

We could hear the solenoid activating but overdrive wasn't there.
Come to find out it was a destroyed unit with metal slivers in the screen filter.:BangHead:

Well, for 800 bucks Gear Vendors apparently will take a bad unit and rebuild or replace it, so this is what he is going to do.
I tried to talk him into doing a 42RH OD swap because we could do it for around 400 bucks total and that includes the shift kit for it, but no go.:D
He has a mildly hopped up 318 so the 42RH would be the ticket in my opinion.
He wants that GV unit.

The GV unit came out of a stockish van and shouldn't have been trashed by too much power, so we figure it must have been abused in some other way.

Bummer.
Click to expand...
Bummer alright...BUT have you delved into the unit & checked out the Damage ?? The gods smiling, IF spares are avail you still might come partially right side up - find an old mechanic who used to work on school buses or GMC's etc, used to 2 speed units, if you aren't confident.
IF a 70's Van & V8 Manual top was an OVERDRIVE, like the 4 speed Mercury Zephyr 6's & some Mustang V8's - little strange OR a sellers 'story'....
The Van could've got rear-ended in o.d. & just lunched the cluster/or dogs on something.. Delve deeper, if you haven't already & luck may be on your side...
Don't tell me ? Feebay/Craigslist/swapmeet ?
Logic says the O.D. trans but having swaped this far.
Just my thoughts.
Don't ya hate it when that happens ?.
Trev

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high.rev.trev said:
Bummer alright...BUT have you delved into the unit & checked out the Damage ?? The gods smiling, IF spares are avail you still might come partially right side up - find an old mechanic who used to work on school buses or GMC's used to 2 speed units if you aren't confident.
The Van could've got rear-ended in o.d. & just lunched the cluster.. Delve deeper, if you haven't already & luck may be on your side...
Don't tell me ? Feebay/Craigslist/swapmeet ?
Logic says the O.D. trans but sealing this far.
Just my thoughts.
Don't ya hate it when that happens ?.
Trev

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Click to expand...
I think we all make gambles with 40+ year old car performance upgrades. And sometimes you roll craps! The Hot Rod gods can be fickle at times.
 
cojohnso said:
I might just bite the bullet and have Gear Vendor re-build. That puts them on the hook for at least some initial functional responsibility. Modifications were done to accommodate? I know it adds more wait time. Something that can be equally tough.
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The floor, driveline, exhaust pipes trans tail housing adapter were all modded for the fit.
Fortunately he could put it back together with the OE trans extension and original driveline so he can still drive the car until a new unit gets here, but he has to send it in with 800 bucks.
MAN I'm glad we didn't shorten his original driveline.:D


high.rev.trev said:
Bummer alright...BUT have you delved into the unit & checked out the Damage ?? The gods smiling, IF spares are avail you still might come partially right side up - find an old mechanic who used to work on school buses or GMC's used to 2 speed units if you aren't confident.
The Van could've got rear-ended in o.d. & just lunched the cluster.. Delve deeper, if you haven't already & luck may be on your side...
Don't tell me ? Feebay/Craigslist/swapmeet ?
Logic says the O.D. trans but sealing this far.
Just my thoughts.
Don't ya hate it when that happens ?.
Trev

View attachment 1715310030
Click to expand...

Well, I used to be a trans rebuilder so not worried there.
The problem is that you can't get parts anywhere, only send them to GV.
He talked to GV about it and they said it sounded like the pump got damaged, which kind of makes sense because it doesn't make any noises or anything just doesn't engage.
To be honest, I really didn't want to get into it any further.
 
What was the initial cost of the used GVOD? 800$ to repair could still be a steal.

I have a GVOD and it's worth it's weight in gold.
 
From what I’ve read and heard is they don’t rebuild yours . You send them the bad unit and $800, and they send you a good unit.
 
I don't understand why people like the GV units. The overdrive ratio sucks.
 
I have a bit of experience with these, albeit earlier units in British cars. The Gear Vendors overdrive is a actually a P-type Laycock which they purchase from GKN and adapt to various US transmissions. They have an internal roller clutch (sprag) which does not take kindly to being operated in reverse (same thing that sent a lot of the old Borg-Warner R10 and R12 units to the scrap bin). They're virtually indestructible unless you try to run it backwards, which results in sudden failure of the sprag rollers which shatter and send bits of hardened steel everywhere. The good news is that they are typically repairable, although the entire unit must be disassembled, which is actually not too difficult. Parts for the earlier A, D and J types found in Austin-Healeys, Triumphs, Jaguars, MG's and Volvos are readily available in this country. GV obviously imports their own parts, and most likely has a contract with a rebuild shop in the UK, so they prefer to exchange units. GKN themselves offer a reconditioning service, and I suspect that's where GV sends them. So, unless you know of a yard full of late manual shift Volvo 740's (used P-type OEM), your best bet may be to bite the bullet and have trade it for a recon unit.
 
TrailBeast said:
.78:1 too high?
Kind of like shifting from 1st to 3rd.
Never drove one before is why I ask.
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Maybe I am confusing them with something else. I thought it was the GV. It was a unit that allows "gear splitting" and I was almost 100% certain it was the GV unit. I've seen people complain about high high the OD ratio was.
 
RustyRatRod said:
Maybe I am confusing them with something else. I thought it was the GV. It was a unit that allows "gear splitting" and I was almost 100% certain it was the GV unit. I've seen people complain about high high the OD ratio was.
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I wish someone would come up w/ a good overdrive only , no gear splitting, that would handle 7-800 h.p. , not cost an arm and a leg ,
and not take a bunch of crazy assed machine work or use someone elses parts to install. (don't want much , huh !)
 
famous bob said:
I wish someone would come up w/ a good overdrive only , no gear splitting, that would handle 7-800 h.p. , not cost an arm and a leg ,
and not take a bunch of crazy assed machine work or use someone elses parts to install. (don't want much , huh !)
Click to expand...
How is Passon Performance accomplishing with their A855 5 speed with .70 5th gear? Ideally I would think you still want to gear 1/4 for 1:1 final gear. And the OD gear is just for that. To knock RPM down for extended use. OD gear was typically weaker. (But I'm sure that has changed with modern trans builds) But it used to be one would never pull a heavy load in high power demand (Let's say up a even slight incline) using an OD gear? Good way to smash your tranny.
 
GV does allow gear splitting but you don't have to use it that way. I only use mine as an OD on the highway. It knocks off 400 rpm on the 50 mile highway cruise with 4.10 gear on my way to and from the track. The lower rpm reduction also keeps a larger duration cam in a usable rpm range to allow passing without kicking the OD out. I bought mine used with a good A999 for $1500.
I've run it at the track using 2nd over in the 1/8 mile and pick up 1/10. I normally run 1/4 mile and turn it off.
 
TrailBeast said:
.78:1 too high?
Kind of like shifting from 1st to 3rd.
Never drove one before is why I ask.
Click to expand...

But to answer the question, yes, that ratio is higher than most overdrives of any kind. The Mopar 4 speed unit uses a .73 OD while the trucks used a .71 OD, so that's a little better. Also, for those who use some of the GM auto OD offerings, they get OD ratios down in the high 60s. I remember threads here where people were disappointed in the OD ratio and basically said the gear splitting thing was the only "advantage" they could think of. That said, that's the only "experience" I've had is reading about other peoples experience. From what I've seen some like them and some don't.
 
mderoy340 said:
GV does allow gear splitting but you don't have to use it that way. I only use mine as an OD on the highway. It knocks off 400 rpm on the 50 mile highway cruise with 4.10 gear on my way to and from the track. The lower rpm reduction also keeps a larger duration cam in a usable rpm range to allow passing without kicking the OD out. I bought mine used with a good A999 for $1500.
I've run it at the track using 2nd over in the 1/8 mile and pick up 1/10. I normally run 1/4 mile and turn it off.
Click to expand...


Same here for the most part. Just OD on the highway. I run 4.56's with 28's and cruise the highway at 2600 at 60mph.

I also run the 1/8th in 2nd OD.

Sometimes in town i'll run 2nd OD

I have zero complaints about the GVOD and have used a couple.
 
RustyRatRod said:
But to answer the question, yes, that ratio is higher than most overdrives of any kind. The Mopar 4 speed unit uses a .73 OD while the trucks used a .71 OD, so that's a little better. Also, for those who use some of the GM auto OD offerings, they get OD ratios down in the high 60s. I remember threads here where people were disappointed in the OD ratio and basically said the gear splitting thing was the only "advantage" they could think of. That said, that's the only "experience" I've had is reading about other peoples experience. From what I've seen some like them and some don't.
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The difference between .78 and .73 OD ratios is 200RPM at any given speed. (or 5mph)


That isn't a huge difference unless you are running some really severe gear.... Now I run 28's with 4.56's and 60mph is 2500RPm.
 
cojohnso said:
How is Passon Performance accomplishing with their A855 5 speed with .70 5th gear? Ideally I would think you still want to gear 1/4 for 1:1 final gear. And the OD gear is just for that. To knock RPM down for extended use. OD gear was typically weaker. (But I'm sure that has changed with modern trans builds) But it used to be one would never pull a heavy load in high power demand (Let's say up a even slight incline) using an OD gear? Good way to smash your tranny.
Click to expand...
I’d go to his web site for information on his 5spd OD trans. I can tell you this about it though, it is not set up (the overdrive) like the Chrysler band aid move.
As far as any towing is concerned, I wouldn’t worry about it because it is a manual and if you needed the extra torque on the road, you would leave it in 4th gear. Since you understand that lugging an engine is bad, the trans is a manual you select the gear in and get the idea of engine rpm and gear selection for best advantage, I don’t understand the worry.
 
Anything higher than 1:1 that enables you to run a 3.5-4.1 axles and end up with a 2.7-3.2 final has got to be a big plus both for a performance increase and an MPG increase.

About the only negatives I've read on the GV is the already posted reverse grenade.
Unless there is a better way, I think I'd wire a cutout triggered by the backup light circuit.
 
rumblefish360 said:
I’d go to his web site for information on his 5spd OD trans. I can tell you this about it though, it is not set up (the overdrive) like the Chrysler band aid move.
As far as any towing is concerned, I wouldn’t worry about it because it is a manual and if you needed the extra torque on the road, you would leave it in 4th gear. Since you understand that lugging an engine is bad, the trans is a manual you select the gear in and get the idea of engine rpm and gear selection for best advantage, I don’t understand the worry.
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Good point about towing. You wouldn't use in any incline. My point is that historically OD gears were weaker by there very nature. Not sure I would be banging one in a speed attempt? Like the drag diesels? I understand they typically have a very high rear gear. But with that low of RPM? They must be using an OD to get there MPH? I toasted an old Ford 4 speed with OD. Towing a relatively light load in OD on a flat freeway. Now it was old and could very well been coincidental. I somehow got it in 4th gear and made it back due to no stopping. Dying halfway up driveway. Truck was old enough to junk thus didn't investigate much. I am inquiring because I'm doing a high horse/torque build at relatively low RPM. (6500 red line) to get anything above 160 MPH? A OD option will be needed with 3.54:1 dana. I'm just worried what any OD would do with 1000+ ft/lbs of torque on it? GV is the leading (and possibly) only real option? (On back of a JW glide that I do have on hand.) But still 1:1 final gear.
 
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I tow cars and trucks half way across the state in OD, on a dolly with my 2000 Dakota.
167,000 hard tuck use miles and never a trans issue (except maybe a delayed 2-3 shift when cold for that last 20K miles) despite the 1990's-early 00's reputation for any MFG having massive trans failures.
The OD turns my 3.92 axle into a 2.7 ratio. Best of both worlds.

The trick is to keep it out of OD until you are at or near cruise speed, and if you want engine braking, turn it off before you prepare to stop.
 
But with that low of RPM? They must be using an OD to get there MPH?
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I'm not fully getting this. or how you mean it in your reply.

I wouldn't be in a OD gear up hill unless the rpm was high enough to support the move. OR, not draging the engine down to low rpm wise.
What Ford OD did you toast? The one that came with the Fox Mustangs? They are low rated in torque handling.
Historically speaking you say. Well, you should take that out of your worries since you know about it and can find out the strength of any transmission and avoid a weak one. So now your fears are unfounded unless you get a weak transmission. Then the fault is your own. All the older transmissions are lowin power handling.
I'm pretty sure Passon has torque ratings to there stuff. Likewise over at Silver State Transmissions.
Reguardless, the torque ratings of the tremacs or other transmissions, you should be available to find out what they can handle torque wise, in foot pounds.

Do you have a need to travel at 160mph? Then gear accordingly. IF you think you can tow with the gear ratio needed for a 160 mph blast, I think your only fooling yourself and laying blame of the crushed dream on the transmission. Before looking at a GV as "The only choice" , an investigation is needed.

OH, 6500 is NOT a relativly low rpm. that would be 5K or lower. FWIW, the factory rated the small block to 6,000 - 6,200 rpm as a max rpm because the oiling system may not be up to par for such rpm duties. The problem is mostly in the oiling passages not always being the same size and failing when pushed beyond the suggested rpm range. Others here (Myself included) have went beyond the suggested rpm factory red line just fine because the oiling passages were larger than normal. I have had them fail as well at 6000 shifts.

This engine limitation also applies to transmissions. Know there available torque capacity as the factory states it and use that as the red line max that you don't want to approach never mind exceed even though others may have exceeded it often with success.
 
GV says there race .78 is rated to 2000 horse for lower R
rumblefish360 said:
Do you have a need to travel at 160mph?
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Yes. I have a very unusual build in an E-body Cuda. The reason I reference towing and diesels is because they better approximate load needs. The motor is 904 ci (6 inch stroke) that behaves more like a diesel. Thus inquiring about how trucks handle the torque and load demands. This is a race application with some light street requirements. (And I do mean "Light")

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