Tremec TKO500 drive shaft length
Thread Starter
Drifting
Joined: Jul 2020
Posts: 1,501
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From: San Diego
Tremec TKO500 drive shaft length
I am in the middle of converting my Muncie M21 4 speed to the Tremec TKO500 and i was told I need to cut down the driveshaft. Does anyone know the length I need to I can take it to the driveshaft shop?
Race Director
Joined: Jul 2015
Posts: 13,082
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From: SW Florida.
install the yoke in the trans and measure the length. don't accept a number another member gives you. they are probably ok, but you need to decide how much free play in front of your yoke and it can vary by yoke length or the amount cut off to modify yoke length.
Thread Starter
Drifting
Joined: Jul 2020
Posts: 1,501
Likes: 323
From: San Diego
So I havent installed the trans mission yet but I am trying to get a jump on getting my driveshaft to the shop because of the turn around time. Would it be wrong to measure from the bellhousing to the rear diff. Then measure the length of my transmission with the yoke all the way in and subtract the two?
For example, if the bellhousing to the differential is 48" and then front of the trans (where it meets the bellhousing) to the output yoke is 25" then my driveshaft needs to be 23". Would this type of thinking actually work?
For example, if the bellhousing to the differential is 48" and then front of the trans (where it meets the bellhousing) to the output yoke is 25" then my driveshaft needs to be 23". Would this type of thinking actually work?
Race Director
Joined: Jul 2015
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From: SW Florida.
put the yoke all the way in. pull it back about 1/4 inch. now slide it out as far as you are comfortable with it. maybe a half inch. that is your wiggle room. make sure you use the center of the bearing cap in the yoke. then measuring the shaft you can use front to front or rear to rear of the u joint caps. that would equal center-center. you also have to be sure the yoke goes in far enough in the first place. many are much better cut down a half inch or so. do more homework.
Old Pro Solo Guy
Joined: Dec 2017
Posts: 8,103
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From: Marlton NJ
You are correct in that the engine to diff measurement on a C3 never varies.
But...
There are several different diff yokes used over the years. A 1310 and a 1330 version. There are also different trans yokes for the TKO. All of these vary in length just a little bit, so they require a specific length driveshaft.
So unless you can get a length from someone who has exactly both yokes that you do, it is a $500 roll of the dice. Why risk it?
It's safer to measure your own, from yoke u-joint center to diff u-joint center. I also think you need another 1/2" of clearance so that the slip yoke does not bottom out.
Or you can buy a complete assembly from Silversport. They supply the trans yoke.
BTW one of the absolute best things you can do is cut the welded in crossmember and make it removeable. It is very difficult to get a TKO installed with a welded crossmember. Possible, but difficult.
I have the trans to diff measurement around here somewhere, if you really want to use it. 29-1/2". From TKO rear of casting by slip yoke to center of a diff u-joint with a 1330 u-joint in a 1977 vette. I got that number from a friend intending to do exactly the same as you. But I still may not risk the roll of the dice, and will just wait and measure my own.
But...
There are several different diff yokes used over the years. A 1310 and a 1330 version. There are also different trans yokes for the TKO. All of these vary in length just a little bit, so they require a specific length driveshaft.
So unless you can get a length from someone who has exactly both yokes that you do, it is a $500 roll of the dice. Why risk it?
It's safer to measure your own, from yoke u-joint center to diff u-joint center. I also think you need another 1/2" of clearance so that the slip yoke does not bottom out.
Or you can buy a complete assembly from Silversport. They supply the trans yoke.
BTW one of the absolute best things you can do is cut the welded in crossmember and make it removeable. It is very difficult to get a TKO installed with a welded crossmember. Possible, but difficult.
I have the trans to diff measurement around here somewhere, if you really want to use it. 29-1/2". From TKO rear of casting by slip yoke to center of a diff u-joint with a 1330 u-joint in a 1977 vette. I got that number from a friend intending to do exactly the same as you. But I still may not risk the roll of the dice, and will just wait and measure my own.
Thread Starter
Drifting
Joined: Jul 2020
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From: San Diego
I actually already installed the removable crossmember. Not the easiest to cut out with the body on but its do-able.
I have the trans and the yoke assembled but not installed. I took the measurement from the middle of the rear diff to the bellhousing and it was 54-1/4”. My overall length of my trans from the front of the bolts to the middle of the slip yoke was 27”. So my driveshaft needs to be 27-1/4”
I have the trans and the yoke assembled but not installed. I took the measurement from the middle of the rear diff to the bellhousing and it was 54-1/4”. My overall length of my trans from the front of the bolts to the middle of the slip yoke was 27”. So my driveshaft needs to be 27-1/4”
Race Director
Joined: Jul 2015
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From: SW Florida.
post a pic of trans with yoke in it. many new yokes have an unnecessary length between trans and u joint. i guess they figured it was easier to shorten than lengthen. and they are right. so shortening it should be considered. goes back to my do more homework. you are not driving this guy to work. if trans is in and you are waiting on a shaft that is optimal length it is preferable to having a shaft a half inch shorter than you would prefer. it will always bug the crap out of you.
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Melting Slicks
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I actually already installed the removable crossmember. Not the easiest to cut out with the body on but its do-able.
I have the trans and the yoke assembled but not installed. I took the measurement from the middle of the rear diff to the bellhousing and it was 54-1/4”. My overall length of my trans from the front of the bolts to the middle of the slip yoke was 27”. So my driveshaft needs to be 27-1/4”
I have the trans and the yoke assembled but not installed. I took the measurement from the middle of the rear diff to the bellhousing and it was 54-1/4”. My overall length of my trans from the front of the bolts to the middle of the slip yoke was 27”. So my driveshaft needs to be 27-1/4”
.
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BTW,,, for reference, mime is (‘75 w/TKO 500). 26-1/2” center to center of caps,,,, but make sure on your car,,,,
Race Director
Joined: Jul 2015
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From: SW Florida.
that is bottomed out? could be 1/4 inch shorter but a quarter inch isn't worth messing with. your length you measured was 27 inches. then you added a quarter. need to subtract a quarter or a half. so right on 60 SHARK's 26-1/2. but you don't know if he has the same length yoke.
Old Pro Solo Guy
Joined: Dec 2017
Posts: 8,103
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From: Marlton NJ
So with the yoke in the trans, and pulled out 1/2" for safety, what is the measurement from the ctr of the u-joint to the back of the trans. You could subtract that from my 29-1/2" measurement.
Assuming you have a late model 71-71 or newer that takes a 1330 u-joint at the diff end.
Yep if you look closely at the two pics above, they are two different yoke casting numbers.
Just checked outside in the garage, my Silversport TKX also came with the Neapco 5221 casting yoke, and it is 5" long as you measured.
No driveshaft yet though....
If I were you I would measure the U-joint size on that other yoke, it looks bigger, it might be for a 1350 u-joint.
Where did you get the TKO from?
Assuming you have a late model 71-71 or newer that takes a 1330 u-joint at the diff end.
Yep if you look closely at the two pics above, they are two different yoke casting numbers.
Just checked outside in the garage, my Silversport TKX also came with the Neapco 5221 casting yoke, and it is 5" long as you measured.
No driveshaft yet though....
If I were you I would measure the U-joint size on that other yoke, it looks bigger, it might be for a 1350 u-joint.
Where did you get the TKO from?
Last edited by leigh1322; May 2, 2022 at 10:42 PM.
Race Director
Joined: Jul 2015
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From: SW Florida.
and how are both of you going to install the driveshaft? bang the cups in with a hammer over your head under the car? modern drive line has back ordered whole shafts. they may sell the removable driveshaft yokes. their number is in this web page of theirs. https://www.moderndriveline.com/shop...977-1310-1330/
Old Pro Solo Guy
Joined: Dec 2017
Posts: 8,103
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From: Marlton NJ
Derek has a good point.
A C3 driveshaft requires a removeable front yoke so it can be removed from the car without pulling the diff first! Unlike any other car I know of.
I already have this special front driveshaft yoke from SST as I intend to use thicker tubing than what they had available. (I have a pretty strong BBC.)
I am just waiting to measure mine first, as I am too gun-shy to buy a custom driveshaft based on somebody else's measurement. I am sure the 29.5" measurement is close, but..... is it close enough? I am not a risk taker with my money.
A C3 driveshaft requires a removeable front yoke so it can be removed from the car without pulling the diff first! Unlike any other car I know of.
I already have this special front driveshaft yoke from SST as I intend to use thicker tubing than what they had available. (I have a pretty strong BBC.)
I am just waiting to measure mine first, as I am too gun-shy to buy a custom driveshaft based on somebody else's measurement. I am sure the 29.5" measurement is close, but..... is it close enough? I am not a risk taker with my money.
Thread Starter
Drifting
Joined: Jul 2020
Posts: 1,501
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From: San Diego
So I think my measurements are sound. I just dropped my driveshaft off at the shop and I told them to cut it down to 27”. Both ends have 1330 u-joints ao it just a matter of cutting it down and balancing it. 27” looked to be precise and I used the measure twice and cut once method but ultimately it will be a $140 roll of the dice