Transmission and differential alignment

[Jeff's First FFR]

Hi all,
While I was crawling around under the chassis checking bolts and torques prior to first go-cart, I noticed that the driveshaft is running “uphill” towards the IRS center section. In other words the output of the tranny (TKO600) is lower than the input of the diff. Looks like about a half inch low. With a driveshaft this short (about 2” plus 2 u-joints), the angle is rather steep. See photo:

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Is this normal? Should I try to raise the rear end of the transmission? I am looking forward to any advice you can give me.

Thanks,
Jeff

[Sdonnel]

Jeff, there are many threads on this and I believe Edwardb has a very good write up in his latest Roadster build log. Not trying to be a jerk, but just to let you know there is a lot of information on the forum. I'm working on angles for an 8.8 as I type this.

Scott

[Jeff's First FFR]

Jeff, there are many threads on this and I believe Edwardb has a very good write up in his latest Roadster build log. Not trying to be a jerk, but just to let you know there is a lot of information on the forum. I'm working on angles for an 8.8 as I type this.

Scott

Hey, thanks. I'll search the forum, but usually I have trouble finding stuff. I'm still new at this. I'll look at edwardb's roadster build.

[RBachman]

Jeff, there are many threads on this and I believe Edwardb has a very good write up in his latest Roadster build log. Not trying to be a jerk, but just to let you know there is a lot of information on the forum. I'm working on angles for an 8.8 as I type this.

Scott

Agreed,

The search function lacks bit of user friendliness, but the info is there. It can be difficult to locate, but its there...now if I could only find the link! LOL. EdwardB's write up is great and should be included in the manual. But there are some others also. Here's an article that's helpful and there are some You-Tube videos that are also helpful. https://therangerstation.com/tech_library/pinionangles.shtml

[Avalanche325]

Search for "pinion angle".

You do not want them in a straight line. Basically, looking from the side, the rear of the transmission points down and the front of the diff points up.

[Jeff's First FFR]

Really?
I will try to find pinion angle.
Thanks,
Jeff

[GoDadGo]

We've shared this video a bunch so I'm sure it will help.

https://youtu.be/Idk3BVDVHq4

[edwardb]

Doesn't look that bad. Keep in mind with IRS that angle doesn't change. So it won't be any more than that. And as others have said, you don't want them exactly in line, if that's what you're looking for. But proof is in the pinion angle measurement. Do you have a spacer under the transmission rear mount? Pretty typical for a TKO to require a 3/4-inch or sometimes more spacer.

[Gromit]

if you use Google, in the search put in

site:thefactoryfiveforum.com pinion angle

you will get about 400 relevant hits and pictures.
the site: keyword is secret that should be told to every google user.

Gromit AKA Chris O

[Bob Cowan]

While you're searching for "pinion Angle", also search for "U-joint Operating Angle".

Read and understand articles like this one: https://therangerstation.com/tech_library/pinionangles.shtml

Remember to measure your angles in two planes, horizontal and vertical. Horizontal is much more difficult to measure.

[Jeff's First FFR]

We've shared this video a bunch so I'm sure it will help.

https://youtu.be/Idk3BVDVHq4

Great video? thanks

[Jeff's First FFR]

Doesn't look that bad. Keep in mind with IRS that angle doesn't change. So it won't be any more than that. And as others have said, you don't want them exactly in line, if that's what you're looking for. But proof is in the pinion angle measurement. Do you have a spacer under the transmission rear mount? Pretty typical for a TKO to require a 3/4-inch or sometimes more spacer.

Thank you,
I have no spacer other than the urethane mount provided. Since Factory Five "did the engineering" it should be correct. Looks like about 3 degrees each at trans and diff. a little much, but if I raise the trans then the angles will no longer be equal. I hope to measure the angles more accurately, soon as I lift it up.
Thanks again, you always have the answer,
Jeff

[edwardb]

...if I raise the trans then the angles will no longer be equal.

I know that's referenced in the linked video. But the angles shown are radically extreme. Far beyond the 1-2 degrees you should see for an acceptable pinion angle. Typically the diff is pointed up slightly to the front, and the engine/trans down to the back. In my experience, properly set up you won't have any issues even if they're not exactly the same.


I have no spacer other than the urethane mount provided. Since Factory Five "did the engineering" it should be correct...

With all due respect to my friends at Factory Five, you assume a lot there. Every build I've done and also helped with has required a transmission spacer to eliminate interference between the tailshaft of the transmission and the 4-inch tube cross member. Plus to get an acceptable pinion angle. Especially with a TKO. I've always been a little puzzled why this isn't at least mentioned in the manual. I'm not the only one. Regularly cited in multiple build threads.

[GWL]

You must also realize that there are many different engine mounts that mount the engine higher or lower depending on the type of Ford part or aftermarket mount you use. There are also a number of different transmission choices that again may differ from one another. Thus FFR has made that mount lower so that all those factors can be addressed adding different amounts of shimming at the rear transmission mount until the right pinion angle is achieved.

Yes, FFR should explain that in their manual and in not doing so makes you wonder if it was intentional or not.

George

[Jeff's First FFR]

I know that's referenced in the linked video. But the angles shown are radically extreme. Far beyond the 1-2 degrees you should see for an acceptable pinion angle. Typically the diff is pointed up slightly to the front, and the engine/trans down to the back. In my experience, properly set up you won't have any issues even if they're not exactly the same.



With all due respect to my friends at Factory Five, you assume a lot there. Every build I've done and also helped with has required a transmission spacer to eliminate interference between the tailshaft of the transmission and the 4-inch tube cross member. Plus to get an acceptable pinion angle. Especially with a TKO. I've always been a little puzzled why this isn't at least mentioned in the manual. I'm not the only one. Regularly cited in multiple build threads.

Yes, that is a lot to assume. with all the different engine /transmission variations available it is sure to be a compromise. I will re-visit putting a spacer under the rear of the transmission. I have a digital angle finder, so after I finish my wheel alignment I will raise the chassis (angle won't change because of IRS) and make a measurement then visit my friendly ACE hardware store. With such a short driveshaft it is best to be more precise.

But, yes at least FFR could have mentioned it. They just left more for us to talk about. I really like the forum.

BTW
https://therangerstation.com/tech_library/pinionangles.shtml is a very good reference.
Thanks to Bob Cowan


Jeff

[Jeff's First FFR]

Doesn't look that bad. Keep in mind with IRS that angle doesn't change. So it won't be any more than that. And as others have said, you don't want them exactly in line, if that's what you're looking for. But proof is in the pinion angle measurement. Do you have a spacer under the transmission rear mount? Pretty typical for a TKO to require a 3/4-inch or sometimes more spacer.

Well, Paul, you are right. The trans needs a spacer. The trans is almost resting on the 4” crossmember. The IRS pinion shaft is parallel to the frame 4” long tubes. The trans points down 5 degrees. The two shaft angles are definitely different. So from trigonometry and 5.5 inches between u-joint pivots tan5*5.5=0.48”.
I thought it looked like it needs more like 1”. Well off to ACE.

Jeff