Hi!
Advanced search was not able to help me so here my question:

What is the typical/recommended clearance of the pressed in pilot bushing to the transmission input shaft?

Background: I installed a new bronze bushing which is supposed to accept the shaft of a Keisler T45 RS tranny. But for some reason the inner diameter of the bushing (pressed in) is 0,001'' smaller than the outer diameter of the shaft... so I need to rework the bushing a little and for this I am looking for my new target diameter...

Thanks
Carsten

 

If you press the bushing in too far there is a lip inside the crank and the bushing ID will be forced smaller. I always leave the bushing out of the crank by 1/8 to 1/4

 

I am aware of the lip inside the crank - this is not an issue.

My research in the internet brought up a range of required bushing to input shaft clearances between 0,001 to 0,008''... shall I go for the golden middle?
Any input appreciated!

Carsten

 

I would contact Keisler for your tolerance dimensions. What is the crank ID ? What is the OD and ID of the bushings your using before installation ?
I've seen cranks pulled out of automatic trans cars with the crank hole majorly screwed up.

 

I've already emailed Keisler but have no answer yet.

The bushing OD of the old muncie bushing and the new T45 bushing differs only by 0,001'' (so they are almost the same). The ID of course is different.

I measured the T45 bushing ID at 0.667'' whereas the inputshaft OD has 0.668''.

 

What are you using to measure the diameters? Are you using a vernial caliper which can measure both inside and outside with the same fixture? Have you calibrated it? You can call around to machine shops in your area and see if anyone has some Standard Units to test your tools on.

Ideally you want no lateral movement. This is very hard to get because the bearing should be greased and the grease has some thickness which needs to be included in the calculation. Grease normally works best between .001" and .004" depending on weight and type...synthetics can work better with less. So, at minimum the bearing should be .002" larger than the shaft...at least that's where I'd start. And, I wouldn't go any more than .008"

 

I used these gauges for the measurements, both are periodically calibrated in my company.





Thanks for the advice!

Carsten

 

All my mics are 1/10,000ths of an inch, you will never see a qualified machinist using calipers on a crank journal unless he is just checking to see if it has be turned before or not.

For holes or bores I use a dial bore gauge and then measure the result of the bore gauge with a 1/10,000" mic. I am not trying to do anything here but help you. I would not use a 1/1000" mic on an engine, you will not get accurate results. As for measuring the inside bore if you are using the calipers for that and that mic for the measuring the shaft you margin of error is probably greater than 1 thou to begin with so you really don't have any accurate measurements there. I use a small bore gauge to measure holes / bores too small for my dial bore gauge.

Again please don't get me wrong I am just trying to relate my experience (I worked in a machine shop after high school ) and how to get accurate an correct measurements so you have a basis for fixing a problem. These measurements can stack up to ( additive ) and by the time you have made 3 or 4 measurements you could be way off line

The first thing you should do is talk to Keisler. These newer transmissions have much tighter tolerances on input and output shaft meaning you can't wiggle them around like a munce or T10

Keisler should have sent you a bearing with kit or recommended one anyway and you must use the bearing the recommend. For my TKO it was a roller bearing and my friend who owns a machine shop didn't want to put that into a $1000 crank but I insisted, never had a problem with it or the one in my previous 406ci.

Bottom line is contact Keisler and talk to them but you have to use the bearing they want you to use. And always check to see how it fits the input shaft before you put it in the crank

 

Pilot bushing clearance to shaft should be .001 to .004 ...

 

Got input from Keisler - with the tolerance of the bushing ID they told me and the given shaft OD I end up with a clearance range from 0.002'' to 0.003''.
I have my bushing machined to where it should be and everything is fine.

Thanks for alle the comments!
Carsten

 

So with Keisler transmissions you have to have pilot bushings custom made ?

 

Keisler must have had some issues with someone mixing up the pilot bushings as I too had a similar issue and just could not figure out why the trans would not mount up to the back of the block. It ended up being the same issue, they sent the wrong size pilot. I just machined, honed it out to the right tollerance and all seems fine! Good luck!

Just a suggestion for anyone else out there just obtaining a new Trans... check the pilot before installing it in the crank...

 

The recommended tolerance sounds good. Don't forget if it is a bronze bushing and it is very tight going into the crank that could compress it a bit

 

You should check your bushing material to see if it is magnetic if it is don't use it, it will make a noise like a Swine going to the slaughterhouse in a few weeks time (if your not using the roller pilot bearing.) The pilot bushings used to be made from Oilite bronze, now there are many Chinese copies on the market and all seem to contain some iron in them and make noises. Autogear transmissions has introduced a line of Oilite bushings after my friend Dave Herlinger prompted them to take care of this problem. I just purchased a supposed Heavy Duty pilot bushing and it is Chinese magnetic bronze, I won't use it.

I am once again swearing off roller pilot bearings after seeing how bad mine looks after only 5,000 miles of service, nothing but, plain bushings for the rest of my life in old C3 Vettes. Yes, I did indicate in the bellhousing to within 0.002" TIR before installation and made sure the crank bore and bearing OD had a 0.001" interferance fit on installation.

Here is a link to the Autogear site: http://autogear.net/whatsnew.php

 

The trans he got was the T45 it is different than the TKO. The part was not machined properly or the regular GM pilot bearing was used out of the clutch kit.