Over Drive add Ons

[Steelawork'n]

Has anyone added an over/under drive gearbox their set-up? I'm doing a little research on it and would like to know what you think. The one I've been looking at is from Gear Vendors: http://www.gearvendors.com/

[dennislbrooks]

GV has an excellent product, it is pricey. I have had mine for 8 years. Originally I had it on a NP205 transfer case. Now it is on the tail of a 350 turbo. Has a high torque and hp rating. They were also used behind the C4 Calaway vette 400 turbos.

The overdrive on mine is 78%. Can be shifted up or down at will like the doug Nash overdrive behind my 85 vette super T10 4 speed - a 4+3.

If I had not already had it I would have a 700r4 in my 67 swb 2wd.

[Steelawork'n]

Nice pic. I'm running the old 4 spd with the granny lo and a 4.10 rearend. The GV is priced the same as a new 5 or 6 spd. Is it very difficult to set up?

[dennislbrooks]

They send excellent instructions and also have excellent phone support. I installed mine on the previous 205 case myself. Then 6 years later sent the 205 adapter back and paid the difference for a 350 turbo adapter. Both times, placed and removed it laying on my back. They keep track of everyone of their units by serial number. They now suggest and as I have in mine GM Synthetic Manual transmission fluid. They used to use regular trans fluid. It uses the same heavy duty driveshaft yoke as a 400 turbo trans. hmmm --new 6 speed or a add-on overdrive ---new 6 speed with its own overdrive is very nice if it will hold up to a 3/4 ton and is certainly a desirable transmision.

[72MARIO]

My dad and I are both looking at getting one for our trucks. He has a 73 1 ton with a 385/400 and 3:73's. With the current exchange rate we might move on one soon. I guess they will take a beating....

[llegos]

dennis, what rear axle ratio are you running now?

[dennislbrooks]

I have the stock 3.73 gear in my 67. It was originally a 327- 3 on the tree. I now turn about 2200 RPM at 60-65 mile per hour in overdrive. Do not ask for exact. I know on my former Toyota 4wd that had 4.10 gears and 31 inch tires I was running about 2500 rpms at 65 mph.

Copperhead is running a GV behind the big block 502.

[gator2511]

I put a G/V od on my 72K10 last summer. Its easy to do and works great. The only drawback I find is that when its on automatic function its shifts hard. I just keep it on manual operation and kick it in when I want it. 3.73 ratio and runs 2100 rpms at 70mph. Pics on my link below.

[dennislbrooks]

I have mine on manual shift with a button the the megashifter T handle. It gears back to 1 to1 when you get below like 16-18 mph.

[Steelawork'n]

Those RPM specs are awesome. At 70mph I'm sure I'm running over 3500...probably over 4200.

What about gas mileage improvement? Getting anywhere close to 20?

[Longhorn Man]

20 mpg...that's askin for quite a bit.
http://67-72chevytrucks.com/vboard/s...d.php?t=172346
out of 146 ppl, only 3 claim 20+ MPG.

[1969 GMC]

Originally Posted by Steelawork'n

Nice pic. I'm running the old 4 spd with the granny lo and a 4.10 rearend. The GV is priced the same as a new 5 or 6 spd. Is it very difficult to set up?

Advance Adapters makes the Ranger III overdrive unit for truck manual 4 speeds. It fits between the bellhousing and trans, and has a 27% (0.73) overdrive.

[llegos]

ouch 1500. man, there is definatly no cheap way around this is there?

[jimfulco]

Here's another option: http://www.usgear.com/v2od.htm

[llegos]

to bad USgear is only for autos.....

[Longhorn Man]

it is a bit steep, but you'll pretty much never break it.

they pop up on e-bay at times

[gator2511]

I'm sure I'm not getting 20mpg, but I get to where I hunt on a 1/4 tank instead of a 1/2. I'm going out today to hunt the afternoon and I'll try to check my mileage just for fun.

[chevy_fatman]

Originally Posted by Longhorn Man

they pop up on e-bay at times

Well, what do you know? there's one right now!!

[llegos]

well none of these will bolt up to my tranny, so it looks like if it ever happens, it will be the 6spd

[TP from Cntl PA]

Originally Posted by llegos

ouch 1500. man, there is definatly no cheap way around this is there?

I mounted a 3spd in reverse in my '71 C-20 with the Cummins............Wasn't sure the swap would work so I needed a cheap OD to try it because the engine runs much slower than a gasser. Wouldn't you know it, the stupid thing worked pretty good. I made a stub driveshaft to go from the second trans to the carrier bearing and it was not balanced, so I had some vibration, but other than that it was a cheap($50 for a bearing to support the output shaft) OD.............We ran it all summer on the farm and couldn't kill it.

I was going to put an NV4500 eventually, but I think I am going to keep my setup, I like having 3 splits per regular gear, it is nice on hills.

[SOON2BLAZE]

There was a post awhile back about the new process A 833 4sp overdrives from late 60- early 70 mopars ( also used in 81-87?) chevy trucks. Sounded like all you needed was the tranny, a GM pn # 452696 clutch shaft bearing retainer, a 23 spline front GM u joint yolk and an autotrans crossmember to support the weight at the rear. Anyone know what I'm talking about or has done this themselves?

[Steelawork'n]

Originally Posted by gator2511

I'm sure I'm not getting 20mpg, but I get to where I hunt on a 1/4 tank instead of a 1/2. I'm going out today to hunt the afternoon and I'll try to check my mileage just for fun.

Can't wait to hear your findings. Oh, and happy hunting as well.

[gator2511]

O.K. here is the latest Poop! I drove up to the hunting grounds at 75mph. The tach read 2400rpms. Mileage was lower than I expected at 13 mpg. Could have been better if I had held the speed down a bit. At times I was running 80mph at 2600rpm. I still think The mileage would also would be better if I had stayed with the Th350 instead of the TH400. I'm happy with the OD unit as I can tow my trailer, drive at highway speeds with good rpms and turn it off and go into 4wd mode in the woods. What more could a redneck want!

[1969 GMC]

Originally Posted by llegos

well none of these will bolt up to my tranny, so it looks like if it ever happens, it will be the 6spd

did you read my post, or not?

[Green Machine]

Originally Posted by SOON2BLAZE

There was a post awhile back about the new process A 833 4sp overdrives from late 60- early 70 mopars ( also used in 81-87?) chevy trucks. Sounded like all you needed was the tranny, a GM pn # 452696 clutch shaft bearing retainer, a 23 spline front GM u joint yolk and an autotrans crossmember to support the weight at the rear. Anyone know what I'm talking about or has done this themselves?

Yep, been there did that. I just got the entire bellhousing, A833 overdrive tranny and shifter from a 81 Chevy half ton. Mine used the same drive shaft yoke as a the 3 speed manual and/or turbo 350. Since your bellhousing has its own crossmember as most do, it may be possible to just hang the A833 from there like the original 4 speed, wish I would have measured the front bearing retainer so I could tell how big it was. IIRC Chevy had two different sizes on their cast bellhousings retainer holes, I think 67 and earlier was differnt size than 68 up but could be wrong and don't remember whch was larger, but if you get the right parts combo It should be a bolt in deal, will have to likely cut a new shifter hole in the floor though.