Gang,
I’ve had a ‘66 Starfire for a while, well, o.k., getting toward 30 years. Maybe you’ve seen some of my posts on this or my other ‘66 big car - a ‘66 98 convertible.

I restored this car, a CA car, with great diecast/stainless trim, finishing in 1998 with a 1970-era 455, E heads, TH-400 auto in its factory Autumn Bronze. I switched the interior from Red (red,red,red) to Parchment per my then-fiancée’s opinion and in full agreement that off white looked better against the Bronze than red,red,red. We’ve been married since 1999, so that’s all good.

The Starfire is still a nice car 25+ years later with various modifications. I’m not fussed about like front disk brakes for safety, Progression Ignition HEI, internally regulated alternator, later stereo, power door locks, power windows, Autronic Eye, Tilt & tele column, and custom 6 way seat using ‘82 Camaro seat stuff.

I’m not a stickler for originality. I might have been, but since the engine in this car was obviously not original. I kind of took that as a license to spec the car the way I want it, as opposed to being slavish about have 1966 Detroit air in the 1966 tires. (We miss you Chris Witt.). For decades, out at the edge of my thoughts about this car has been a manual transmission…

Just recently I bought some fairly rare manual transmission pedals & related Z-bar/mechanicals to get going on a potential conversion from TH-400 to M21 manual transmission. If I have it right, Olds made about .5% (half a percent) of big cars as manuals. I have no interest in BS’ing anybody about how the car was delivered, but I’m curious about how a manual transmission big body would drive. So I’m kicking around what it would take to convert the car to manual.

Other than the pedals, what else do I need?
If I understand the challenge, I need either replace the auto flex plate with one drilled for a manual bearing or replace with a manual 425/455 flywheel. The engine runs great, but could use a re-seal of various seals that seep/leak after 20 years. That means pulling the engine to replace the flex plate is not a single-purpose operation.

Then I’ll need to get a BOP bell housing to house a clutch, and accept the pedals. They seem available. Well and a clutch & clutch plate…

Then I’ll need to punch/drill the firewall for the additional pedal, mount the pedal assembly on the firewall & connect (likely weld) my manual parts to the frame in the right place to have the clutch work right.

Then I need a long tail (not Cutlass) M21 or compatible manual transmission to feed torque to the driveshaft. I accept that I might need to modify or replace the driveshaft as part of the process. I might even need to build/modify the transmission crossmember to support a new manual transmission.

Then I might need to modify the transmission tunnel to accept a wider diameter manual vs TH-400 transmission.

Jim Schulz of AZ reports that big body manuals had some kind of hump to accept the M21 into a B-Body. I don’t think this is wrong, but I’m theorizing I can do without so long as I isolate the transmission in the proper position and just pass the shifter up through the body. I know I need a hole in the right place, I’m not sure I need to make it perfectly factory to get the job done watertight and cosmetically correct.

This brings up the question of interior trim. From what I know it looks like Olds used the 64-69 Cutlass/442 console and top plate for the big cars. As far as I know, they didn’t cast any thing unique to the big cars. Am I right on this point? So then my trim shopping is basically looking for a 64-69 Cutlass/442 console and installing it in the right place.

Lastly I’ll need some way to activate the reverse light switch. I could cobble something up, but Olds had to have provided for this for the A bodies. I don’t think this will be hard, but I don’t want to be ignorant either.

So - long winded way of saying, what am I missing? I’m not so far into it yet that I can’t reverse course, but am curious about a manual shifted ‘66 Starfire. In my area, with professional help, I’m guessing I’m solidly into high 4 figures for the conversion, but I don’t know if I really understand all that is involved.

Anyone care to school me up on Automatic to Manual conversions on 65-66 Big Oldsmobiles? Looking forward to your opinions, thoughts, advice and warnings.

Thanks in advance,
Chris

 

I really think you would want an M-20 (Wide ratio) for a lower first gear to start a big car rolling.

I don't think you need to alter the firewall or transmission tunnel.....beyond the hole for a floor shifter and clutch rod.

Do you have a bench seat ? OR bucket seats ? I saw a '66 B body (NEW) with a 4 speed and the shifter came up through the floor fairly close to the front edge of a bench seat. It also didn't have a console.

 

Thanks for checking in. Hadn’t thought too much about the ratios. Good point. I have the impression that the key point with big cars is the long tail Muncie, but if I can find wide ratio that would be preferable for off-the-line to close-ratio.

As it happens my ‘66 Starfire was delivered with ‘66 Strato buckets and the automatic console. A few years back I bolted in ‘68 or so Strato bucket replacements from Classic Industries to acquire the seat back locks which keep the seats from folding up on you in an accident. While I was at it, I had them add the optional headrests too…

The seats are clad in ‘66 Starfire pattern Madrid grain parchment vinyl as you’d expect - looks ‘66-normal except the later year seat back locks. This upgrade is typical of the kind of thing I do in the name of optimizing factory-correct vs. safety on this factory-looking but sort of multiyear-mutt car.

So the cabin is set for a new console to complement the factory-ish buckets, but I’m trying to be sure I’m understanding the size/cost of the effort before acquiring more expensive & rare parts….

Cheers
Chris

 

Forget the (always) outdated factory ratios and look into the offerings from Autogear. The M23z would work really well in a big car.

Also you might consider a hydraulic clutch kit. The expanding throwout bearing setup is hard to beat. Super simple and easy to plumb up.

Sourcing the long tail muncie will be the hardest part.

The juice will definitely be worth the squeeze!

 

Having been involved with a 65 Starfire auto to stick conversion and owning a 66 Delta factory 4spd I would ask for a picture of the pedals etc. that you now have. The crank would need to be drilled for a pilot bearing or at least the center hole made deeper with a conversion bearing which sometimes cause a problem. You would need an early 64-67 flywheel, tab on frame for Z bar, and other stuff.

 

Yep, never seen nor heard of a long tail Muncie. That's going to be your unicorn/needle in the haystack. You'll definitely want the steepest 1st gear you can find. I'll be posting an M22W (2.56 1st gear) for sale in a day or 2.

 

I sometimes see the long tails at swaps, Carlisle mostly. Last Thursday while there Ed Hartnet had one for sale, he is a trans builder.. They are much more common in Big Pontiacs but Olds is unique as the port for the speedo cable takes a plug as the speedo is driven from the left front wheel bearing cap not the transmission. Somewhere I think I have a front yoke that is supposed to be specific to the b body Muncie cars, dont know if this is true though...

 

Just out of curiosity: are they usually 10/27 or 26/32 in/out?

I would think it easier to use a standard length, then modify the cross member and driveshaft.

 

Get a Tremec TKX five speed and don't look back.

 

10/27 the ones I have seen.

 

 

Except of course when in Reverse.

 

Gang,
Many thanks for your thoughts. Mind if I continue to tease this out?

Yup, can find the long tail Muncie, not easy, but doable. I’m very interested in the Tremec TKX - looks like a good package, but that raises the question of traditional vs. hydraulic clutch and I’m beyond ignorant on the pluses & minuses there. Is it larger than my factory transmission tunnel? Am I cutting the floor pan?

All my Oldsmobiles have been TH-400s and the last manual I had was a 1996 Mazda MX-6 (V6!) which was really fun. After that, well, I was a Dad & automatics were preferred, if not the rule. For the record, my wife can drive a manual, no problem at all, but she likes small cars - which mid-60’s Starfires/98’s are not…

Looks like the Tremec is a package, which works for me, but I’d be going for Old’s looking cosmetics - notably the clutch pedal & console. I’d be completely open to Tremec 5 speed and hydraulic clutch. Or will it work with a traditional factory-style clutch? Can these parts be persuaded to interoperate? The conservative part of me says go with GM factory (now rare) stuff since it’s known to work together. The other part of me says accept that manual transmissions have moved on since, uh, 1966, and get with the modern 5 speed program…

Thoughts? Thanks in advance.
Cheers
Chris

PS: Olds content: I redid my 15” Monte Carl fake factory wire wheels with Olds tri-bar spinners today. They look like car jewelry. Well, at least to me…

 

Most reports say the TKX fits with little or no modifications. If your not married to the Muncie platform, I have heard nothing but good things, plus you can get some great ratios on the gearset and overdrive. Much cheaper than my high end Muncie and a future gear vendors overdrive.
Lots of great choices on clutch packages so really your only choice is mechanical linkage or hydraulic release bearing. I have ran both and prefer mechanical, but I bet I am in the minority.
I think its super cool that your putting a manual in your Starfire.

 

Could be a silly question (I'm sure other posters will be pleased to advise me if it is) but: is it really necessary to locate a long-tail Muncie (which must be very hard to do) if you're going to be looking at a custom/fabricated driveshaft anyway?

 

Chris, here's a few notes on driveshafts...

Longer-wheelbase GM cars generally had the long tailshaft transmissions. Even my 1970 A-body Vista Cruiser had a long tail-shaft T-400. The reason was to keep the driveshaft length short enough that the GM driveshaft suppliers could easily make one. Longer driveshafts need special construction and balance.

Today there are many custom driveshaft manufacturers. I used Denny's for my Vista Cruiser. Here's the short version of what he taught me.

Every driveshaft has a critical rpm. This is the rpm where vibrations become self-reinforcing and destructive.

When you have an overdrive transmission, such as the TRX you are considering, the driveshaft turns at higher rpm.

A longer driveshaft has a lower critical rpm. To raise the critical rpm requires a stiffer or lighter (or both) driveshaft. In my VC, Denny pointed me toward a 3.5" o.d. shaft made of an aluminum metal matrix alloy. If a 4" shaft would have fit, I could have used a cheaper steel driveshaft.

To get an estimate, you will need to provide the driveshaft maker with these things:
1. the length of the new shaft between U-joint bearing centers, accounting for tailshaft difference, etc.
2. the highest rpm of the shaft (take your engine's redline and your car's top speed, tire size, and overdrive ratio into consideration)
3. the smallest clearance along the driveshaft (I had to enlarge one section on my VC to even allow a 3.5" shaft)
4. the engine horsepower

We'll check your calculation with number 2 if you need it.

And if you ask the driveshaft maker for the critical rpm of a specific shaft and they say, "what" or "you don't need to worry about that." Run away.

When you get it assembled, you will also need to make driveshaft angle adjustments. Make a post when you get there.

Gary

p.s. one of our members with a Vista had a GM driveshaft fail because of use with an overdrive transmission. It was exciting to read about but not something you want to replicate. At least it was on a chassis dyno, so the car didn't do the pole-vault thing.

 

This isn't entirely correct.

Driveshaft RPMs have nothing to do with the transmission. The only things that affect driveshaft RPMs are rear axle ratio, tire outside diameter, and road speed.

Yes, every driveshaft has a critical speed (RPM). This is where vibrations excite the natural frequency of the shaft, causing vibrations. Longer driveshafts of the same diameter have a lower natural frequency, which means that the natural frequency is more likely to coincide with the shaft RPMs at freeway speeds. There are several ways to increase critical speed (natural frequency). The easy way is to increase shaft diameter, since moment of inertia (stiffenss) goes with radius to the fourth power. Another way is to use a two piece driveshaft with a center bearing. My 62 F85 does this because the low floorpan limits allowable driveshaft diameter. Long trucks (like my crewcab dually) similarly use a center bearing. Using a material with a higher modulus of elasticity (like carbon fiber) also increases critical speed.

 

[QUOTE=joe_padavano;1627662]This isn't entirely correct.

Driveshaft RPMs have nothing to do with the transmission.[QUOTE]

You are correct. Thank you for being our fact checker, Joe.

 

It stands to reason a gear swap was done along with the OD trans..

 

That may be.

Alternatively, the transmission OD may have allowed the top speed of the car to increase without exceeding the engine redline.

 

Hi,

Another thing I didn't see mention was rear axle ratio. The full size cars don't have a big offering of lower ear ratios. Factory cars had most likely a 3.23 ratio not bade with a wide ratio 2.52/2.56 1st gear.

Yours being a automatic could be anything from 2.56 to 3.08 not the best to get a car going without being hard on the clutch.

Regards,
Jim

 

Many thanks for your thoughts on the driveshaft.

I never knew about the critical lengths, but it makes sense that you’d want to design the shaft to avoid the frequency that would damage/shatter it. I was pretty sure there’d need to be custom work on the existing shaft, or maybe a new one. Once you get that far into it, you might as well get it the right length, get it balanced and be formal about it.

My Starfire has a 3.23 open rear gear, and as it happens I have a spare set of 3.08:1 gears in storage. The tires are 245/60 R15 Goodrich T/A Radials on 15x8 wheels. With current TH-400 the engine turns right around 3,000 rpm at 70mph. On the last really long freeway drive with that setup I got 14.5 mpg on the freeway going 60-70 mph from SF to LA and back. Around town since then I’m getting around 11-12 pretty consistently.

Having tried everything from 2.93 to 3.08 to 3.23’s over the years, I really like the 3.23’s the best and would aim at keeping it unless the gearing from the transmission was really spinning my 455 at much higher RPMS for the same given freeway speed.

I don’t want to beat this to death, but any suggestions from here remain welcome. Like A/C before I owned an A/C car, manual transmissions are a mystery to me.

I’ll keep you all posted on how / if the project goes.

Cheers and many thanks for your thoughts so far.
Chris

 

Chris, when I changed from a T-400 to a manual transmission, I found that my revs dropped 4.5% at highway speed because the torque converter slip was eliminated.

If you get an overdrive transmission, your revs will drop again in proportion to the overdrive ratio.

For instance, if you chose a TKX with a 0.72 overdrive 5th gear your engine speed at 70 would drop 4.5% because of no torque converter = 2865 rpm and it would drop another 28% because of the overdrive ratio = 2065 rpm.

And, on the subject of choosing ratios, for a responsive feel from the start, you would try to get the first gear ratio times the rear axle ratio to be near 10.

For example, a rear gear of 3.23 times an available TKX first gear ratio of 3.27 = 10.6:1. This would give a LOT of torque to the rear tires and would need an anti-spin to be effective.

Even a rear gear of 3.08 would be suitable, and your 70-mph engine speed would drop another 100 rpm.

Based on my experience, that last engine speed would increase your highway fuel economy about 4 mpg including the ~1/2 mpg gain from no torque converter.

Gary

 

i have a long shaft muncie and bell housing sitting in my garage from a 66 pontiac grand prix.which is the same trans,but as mentioned olds does not have a speedo drive.one other thing i don't remember seeing is the front driveshaft yolk is small er on the 4 spd then the th400.

 

Why? And in any case, Chris is only talking about changing his TH400 for a manual trans. Gear sets for the full size cars are unobtanium.

 

The 1966 Starfire came standard with 3.08 gears with the TH400. MT cars got 3.23s. 3.42s were the only other option and are nearly non-existent. I also don't get the whole "lugging the engine" concern with an OD trans. I've owned five 1980s Oldsmobiles with 200-4R and rear axles ranging from 2.73 to 2.41. Even the pavement-ripping VIN Y 307 has no problem. The trans kicks down. Yes, you have to manually shift out of fifth on an MT car. That's kinda how you have to drive a manual trans. The TKX has a 3.72 first gear, which will be a HUGE improvement over the TH400's 2.48, even with the switch pitch.

 

I wasn't aware a 70 Vista was a full size.

 

Go back and read the first post. Chris has a 1966 Starfire, which is the topic of discussion in this thread. And while the Vista is an A-body, it's 121" wheelbase puts it in the same driveshaft length as Olds full size cars, which is why it uses a long tail trans.

 

Read the whole thread. I wasn't responding to him.

 

So again, the Vista uses a long-tail trans because of the long wheelbase.

 

Again, read the thread. I was talking about a possible gear swap in a vista, which doesn't have unobtanium parts. With an OD swap the factory driveshaft length is meaningless, especially with a long tail trans. Why are you trying to beat your chest so hard here?

 

And that was obvious in a thread titled "Converting a ‘66 Starfire from TH400 Auto to Muncie 4 speed manual"

 

Thread wobble is real and happens everyday. No reason to roll your eyes.

 

I will second ,third & forth this ^^^^^ The only way to go !!!

 

I did a Tremec in my 68 S. It had an overdrive of .64. I could finally drive the car wherever I wanted to. So glad I did it.

 

Gang,
As always great fun to get your thoughts. To those of us reasonable into this hobby, this forum remains an invaluable resource thanks to all of you. Job well done.

I'm concluding that

1) Tremec TKX wins over the rare long tail Muncie 4 speed transmissions unless I'm a purist. On this one, as a not-too-purist, I'm going for function over form. If I move forward, TKX would be my choice based your recommendations. Many thanks for schooling me up on the world of manual transmission advances over, say, the last 60 years.

2) I'll have to get a custom-ish driveshaft made. It would be smart to balance it along the way. 3.23:1 gear ratio should be fine, though if I could ever find 3.42:1 big car gears, that'd be more fun...

3) I'll need to get the flexplate / flywheel modified to accept a manual trans pilot bearing, which means pulling the engine. This is o.k. for me because this good-running 455 is seeping in a few places & could use 25 year old seal replacement anyway...

4) I'll need to get a BOP bellhousing

5) I'll need to decide on hydraulic vs. manual clutch. Opinions, pro's & con's most welcome here - I haven't a clue. What are your views, experiences & opinions?

6) Cosmetically, having acquired the big car clutch/brake pedals, I'll need to get a nice 64-69 Cutlass console, top plate & shifter (ideally a hurst shifter, right?). Then, since the tkx is 5 speed, I'll need to custom make a shift pattern appliqué/bezel/badge that includes that 5th gear in factory pattern to make it correct-ish, but subtle.

7) Guessing I'm into $5,000-6,000 for parts, plus labor I probably can't do. I must think carefully about whether this pencils out for my wife & me for the next decade or so...

From where I sit this thread is wide open for any further advice you all have to volunteer, warn, or give. Little reversible projects are 1 thing. This is a permanent change. I want to go forward (or not) with full knowledge aforethought.

Cheers
Chris

 

I love how everyone is on the TKX tip. I haven't seen anything but marketing hype. Historically, 5 speeds don't do well under the abuse of Olds torque. I'm not sold, and opted for the GV.

 

Fleming, I put a Tremec in back of a stout 455 and it didn't miss a beat. The TKX has a 600 ft lb capacity. I doubt he will be seeing that much. The over drive clinches the choice for me. When I did mine I wanted to be able to drive the car on the freeway w/ out the attendant high RPM. The Tremec delivers this. Much less wear and tear on an Olds engine which doesn't appreciate high RPM. The drivability factor is what the op is looking for, isn't it? Anyway, here's a pic of the Olds I put my Tremec behind. I used the old style throwout bearing and fork setup. It worked fine. Hydraulics are great but the mechanical setup is IMO easier here.

 

What about using a Borg Warner T-50. I've had one behind my BBO '70 Cutlass for a while, but was concerned about a heavy BB car with that trans in the middle.. The T-50 is the original MT 5 speed that came with the Starfire and Monza, it fits and gives you an overdrive gear. Now it's only rated at about 150 ft-ls of torque, but as long as you don't hook, it would probably work.OK. It fits as it was designed for that car and it lived in mine with a build 455.(around 500 HP and 295-50x15" tires).

I put a Tremek TKO 600 in to replace it and it is MUCH bigger in the tunnel area The TKX is supposed to be a better fit..You may have to pie cut the tunnel to make either fit.

I have a good (and one bad) T-50 that I had in my W-31. That I need to get rid of. Wonder what shipping would be from TN to Cali on that??

 

No offense las, but this should be a non starter. Why go to the trouble of converting it to a manual and then put a substandard transmission in it? Fitment? In my 68 we cut out the whole tunnel and just made a new one. W/ the carpet down you couldn't tell it was there.