Author Topic: TKO600 5-speed short input shaft is too long.  (Read 974 times)

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Clark Coe

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TKO600 5-speed short input shaft is too long.
« on: September 13, 2019, 03:22:30 PM »
I need help with the input shaft fitment of a new TKO600 five-speed installation in my 1968 Mustang equipped with a stock 390 with a stock Ford crankshaft. The TKO input shaft is too long and splines hit the bronze input bushing. When bolting the new transmission to the stock Ford GT/CJ bell housing (C6OA-6394D), the input shaft interferes with the input bushing with about .060” before the trans and bellhousing meet.



I ordered the TKO600 with the short input shaft option for Ford FE engine. The TKO600 as delivered, has the distance from the transmission mounting surface to the tip of the input shaft at 6.672”. The 428CJ big in-big out (RUG-AE2) close ratio top loader I am replacing measures 6.03”. That is a .642” difference. I was expecting new transmission to be a complete bolt-in and not to be this far off.



The stock Ford bronze bushing is fully seated into the crank flange. The bushing has always sat approximately .100” proud of the flywheel flange, is this normal? This old configuration has functioned perfectly in this car with this top loader for the last 39 years.

For a solution, it may be possible to remove the bushing and machine a step relief in the backside, outside diameter and move the bushing deeper into the crank flange. The pocket depth of the hole in the crank flange in deep enough to accept the current (short) input shaft. There must be a two diameter step in the crank flange hole.

I do not want to disassemble the transmission and have the input shaft shortened at the splines. Is there a better way?

Is the 6.03” input measurement from my Big In/Big Out correct? I have searched for this measurement and have not been able to confirm the 6.03”.

Did I really receive the short FE input option? My vendor said that I did and that I have an unusual transmission and bell housing.  :-\



Do 390 top loaders have different input lengths than big in/big out 428CJ close ratio top loaders?

I need some expert input please, summer is almost over and I have not driven my Mustang this year.
« Last Edit: September 13, 2019, 05:13:56 PM by Clark Coe »

67428GT500

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Re: TKO600 5-speed short input shaft is too long.
« Reply #1 on: September 13, 2019, 04:25:10 PM »
Modern Driveline.  208-453-9800
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AlanCasida

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Re: TKO600 5-speed short input shaft is too long.
« Reply #2 on: September 13, 2019, 04:51:56 PM »
From the photos and your measurements it looks like you didn't get the short input option. When I did my first conversion the BBF option was not available so I had to get a spacer made by McLeod and it was nearly the same thickness as the difference you are showing.

67428GT500

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Re: TKO600 5-speed short input shaft is too long.
« Reply #3 on: September 13, 2019, 05:10:50 PM »
Alan is correct. You'll need the spacer. Modern sets them up so other than the disc/spline pattern it fits in all the factory locations, including the shifter.
They also give those of us who are veterans a 10% discount. Great service as well.

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« Last Edit: September 13, 2019, 06:56:13 PM by 67428GT500 »
'Once you have tasted flight, you will forever walk the earth with your eyes turned skyward. For there you have been, and there you will always long to return.
'The American dream is alive for those unversed in the ideology of victimhood. - Thomas Sowell

blykins

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Re: TKO600 5-speed short input shaft is too long.
« Reply #4 on: September 13, 2019, 05:21:37 PM »
Use the short input shaft kit, not the spacer.  The spacer compounds concentricity tolerances which you don't need.  Dialing a bell in by itself can be challenging, I wouldn't add to it. 

The short input shaft kit is about $300 and it takes about 15 minutes to swap it.  It's not like working on a Toploader, the input shaft is keyed and it slides right out after you take the bearing retainer off.  The kit comes with a bearing retainer and an input shaft. 
Brent Lykins
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Clark Coe

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Re: TKO600 5-speed short input shaft is too long.
« Reply #5 on: September 13, 2019, 05:27:46 PM »
This was Modern Driveline in Caldwell, Idaho. The best numbers I can find is that a small block toploader should have a input shaft length of 6.49" and a big block toploader will be .38" less than that at 6.11"....this was from a Richmond Super Street 5-speed resource chart. 6.11" is sort of close to my field measurement of my BI/BO toploader of 6.03"

Clark Coe

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Re: TKO600 5-speed short input shaft is too long.
« Reply #6 on: September 13, 2019, 05:33:10 PM »
Brent, Thanks for your reply. I would have purchased this from your business, but I really wanted the lowered cut down case to clear the brace in the tunnel.
I DID order and pay for a short shaft option. I am guessing that maybe I received a GM input shaft.

blykins

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Re: TKO600 5-speed short input shaft is too long.
« Reply #7 on: September 13, 2019, 06:31:32 PM »
Clark, I apologize for not doing a good enough job of reading your post.  I see what you're talking about now. 

A short input TKO should bolt up to any FE bell, with the exception of a truck bell. 

A typical TKO input shaft is about 7.2" long.   A standard TKO depth bellhousing is 7.050" from the block flange to the trans flange, so if you were to sit it on the floor block-side down, and measure from the floor to the trans face, it would be 7.050". 

A Toploader bell should be about 6.400" deep if measured the same way that I just described.

So, if you compare a standard length TKO input shaft and a short input shaft, there's gonna be about 3/4" difference. 
 
Brent Lykins
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My427stang

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Re: TKO600 5-speed short input shaft is too long.
« Reply #8 on: September 13, 2019, 08:07:00 PM »
Brent, Thanks for your reply. I would have purchased this from your business, but I really wanted the lowered cut down case to clear the brace in the tunnel.
I DID order and pay for a short shaft option. I am guessing that maybe I received a GM input shaft.

My short input was the same length as my RUG-AE2, I think you may have the wrong one

---------------------------------
Ross

- 70 Fastback Mustang, 489 cid FE, Victor, SEFI, Erson SFT cam, TKO-600 5 speed, 4.11 9 inch.
- 71 F100 shortbed 4x4, 445 cid FE, headers, RPM , 1000 Holley HP, Bullet SFT cam, 4 speed

BattlestarGalactic

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Re: TKO600 5-speed short input shaft is too long.
« Reply #9 on: September 14, 2019, 03:24:21 AM »
Your toploader is a big block version.  The TKO looks like the wrong one.

Can you line them up side/side and compare the spline and snout lengths?  Is it just the snout or are the splines too long also(likely)?.

If it's the splines, then it needs a different shaft.  If just the snout, then a cut off wheel will fix it easily.

Cyclone03

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Re: TKO600 5-speed short input shaft is too long.
« Reply #10 on: September 14, 2019, 10:10:13 AM »
Battle star  may have hit the nail on the head. Way back in the 90’s I had the input shorted by .600 to fit my top loader bell. The look after the spline cut was like yours,it looks like they didn’t trim the pilot shaft back . See that groove? That is the old end of the splines.

machoneman

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Re: TKO600 5-speed short input shaft is too long.
« Reply #11 on: September 14, 2019, 10:46:59 AM »
Looks like a snout cut will bring it all back inline.

Separate issue but the diameter of that TKO input shaft looks a lot smaller than the old T-loader shaft. Can't therefore believe that at least the shaft is as strong as the old Ford piece.   
Bob Maag

blykins

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Re: TKO600 5-speed short input shaft is too long.
« Reply #12 on: September 14, 2019, 11:36:40 AM »
Can't therefore believe that at least the shaft is as strong as the old Ford piece.

You'd be surprised......

I've got TKO 600's, unmodified, behind 740 hp BBF's.  They're very stout and their torque rating is rated "continuously".   
Brent Lykins
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machoneman

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Re: TKO600 5-speed short input shaft is too long.
« Reply #13 on: September 14, 2019, 12:31:14 PM »
Interesting. Must be tougher steel than Ford used.
Bob Maag

blykins

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Re: TKO600 5-speed short input shaft is too long.
« Reply #14 on: September 14, 2019, 12:38:46 PM »
More splines help as well.
Brent Lykins
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