The Stovebolt Site Forums The Shop Area Engine Shop 4-Speed Saginaw w/od

I've got a regular Sag 4-speed now but am considering something with overdrive. I've heard lots of discussion here about the t5. Anybody have experience with the Sag with o/d? How does the o/d operate? Which do you think would be the better way to go?
Thanks for any comments.
Dennis

Is this the /od you are talking about?

http://www.chevytrucks.org/tech/overdrive.htm

It would have the advantage of not having to change trans mounts or drive shaft.
It would be very similar to the '84-88 Vette 4+3 Overdrive. It is a Super T-10 with a 2spd automatic overdrive tailhousing and controlled by computer. The computer locks out 1st over, hence the 4+3 = 7 speeds. The problem with this setup is that the computer doesn't always shift when you expect or want it to.
This site just gives a little info on the od and the wiring for it

http://www.classictruckshop.com/clubs/earlyburbs/projects/over/drive.htm

Dennis, Jack Halton of the Inliners club ran one for years behind a 302 GMC.He never had problems. I can't say if he was rough on it,but I do know his truck piled on a lot of miles.He sold the trans last year and installed a WC T-5 in the same truck. if you go to Inliners.org, maybe he will answer your questions from his experience.

Dennis both trans are weak behind a 302.The saginaw will break if your rough on it as will the T-5. If your easy on the trans the saginaw will work.The WC you will pay big money for.I really think the person tony is talking about is using a camaro t-5 with a s-10 tail shaft.Those are pretty cheap but still a little brittle. I would go with a T-10 or Muncie 4 speed with NO overdrive.Dont even consider the 4+3 vette box ,its one of the worst on the market.Seen those break a lot.Just my nickels worth. Oh the weak t-5(s-10 box) i have in my truck now has over 350,000 miles on it with out a wimper.All depends how you drive it and change the fluid.

Yes a camaro box. what about the Mustang T-5? Is that a more rugged box? One Inliner is running a Fomoco 4sp top loader with an adapter behind a built 292 Chevy.He has the one with the lower 1 st gear ,so he can run a 2.90 gear in the back for nice highway cruising.The wide ratio Muncie has only a 2.54 first gear.For everyday driving you might need a 3.36 gear for good power at low speeds.

Tony the top loader would be a excellant choice for the 302.But It has to be adapted.With the 292 it will bolt in by using a scattersheild(lakewood makes it)or plate. I have bought swap meet scattersheilds cheap that the oval track guys use cause they cut the bottom off(no good for the drag guys).You can take those and redrill them and weld nut on the inside.But it still wont work for the GMC.The muncie M-20 has a 2.52 1st 1.88 2nd 1.46 3rd 1to1 top gear
The M21 Has a 2.20 1st 1.64 2nd 1.27 3rd 1to1 top
The M22 is the same as the M21 but straight cut very noisy gears.(probably wont find one anyway,they have a fine spline input)
T-10s have a bunch of diff ratio's some of the first gears are as follows 2.43 2.64 2.88 .

The six speed i have been thinking about with the blown 235 has a 2.66 1st 1.78 2nd 1.30 3rd 1.00 4th 0.74 o/d 5th 0.50 o/d6th but its gonna take a hand fabbed plate and some linkage screwing around. I will really have to keep the speedo disconected so the wife dont see the top end on that one.LOL

Oh reasons i dont like the saginaw 4 speed overdrive.For one thing you should NOT be shifting all the gears in O/D only 4th. The next is it fee wheels and i feel is not the safest thing to have happen coming down a hill and lift off the gas to help you slow down and no enginge comp to help.Sorta like the sign's you see on a big hill DONT coast.It aint smart cause after the brakes are hot your going for a big ride with no way to get back in gear.They also like to roll away every now and then if you forget.Plus anybody that has one thinks its worth gold.My vote skip the 4 gear sagnaw with the O/D it had its palce years ago when we had nothing else but with all the good overdrives out there why mess with a 30 year old box???Parts aint cheap either.If you got one use it,if you can buy one for 50 bucks use it.If you got to pay 100-400 bucks for it leave it were it sits .Just my thoughts on the saginaw(hey i broke a lot of them in my youth or is that yout)

what 6-speed are you thinking of Phat? T-56?

Thanks for the comments and web links. Phat, I had a 3-speed with o/d in the truck when I got it. It made a lot of funny sounds and I didn't want to get into it so went with the Saginaw. I was a free-wheeler too at times. I didn't like that part. I thought something was wrong to make it do that but I guess that's part of the design! Gees!
I don't think I'll go for the Saginaw o/d. Thanks again. I'm going to ask a question about rear gears but I'll start another thread for that. I'll post the question to Inliners too. Thanks Tony.

Racecarl pointed the way to the New Process A833/89mm/MY-6 GM 4 spd overdrive. Used only on 81-86 GM trucks, it is a little hard to find. I just installed mine behind a 66 250 in a 52 Chev 1/2 ton with no problem. Not on the road yet, but I don't anticipate any trouble.

See it at
http://www.homestead.com/chuckthetruck/page12.html

Somebody told me my name came up here so, here is my experience with the Saginaw overdrive. Yes I did run one for years. It held up behind by my 302 with no problems whatsoever, about 45K highway miles and occasional dragstrip usage. So there is no problem whatsoever with durability.

If you understand how a TRUE overdrive works (and yes, there were special sections in the owners and shop manuals) you would know that free-wheeling is an on-demand function via a manual lockout cable. The tailshaft planetary gears, and the free-wheeling clutch, can only be engaged when the lockout lever allows the solenoid to move the blockers into position. So you have complete control over when you have free-wheeling, which is a very useful feature on flat ground (saves gas). Otherwise, you have a direct drive 4-speed transmission. And the factory wiring prevented abuse by including a speed governor. Bypass this feature at your risk.

Also, a lesser-known side benefit is that with free-wheeling engaged, the FW clutch synchronizes the entire transmission, allowing leisurely upshifts or downshifts without use of the clutch.

I really loved my overdrive, and the only reason for changing to a T5 was that parts for the OD are becoming hard to find. Solenoids, planetary gearsets and clutch cages are NLA from GM or aftrmarket sources. The T5 has better prospects. Time will tell how it holds up, but I know I will miss flicking that switch and watching the RPMs drop from 2400 to 1800.

- Jack