Porsche/Ford TransAxle alignment-runout

Paul Proefrock

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I am looking to become more familiar with the process of aligning the Ford Crankshaft with the transaxle input shaft.

My background has been front engine, rear wheel drive and I know the importance of aligning the bellhousing with the crankshaft. The TKOs used in my cobras were very sensitive to this and I am aware of the issues when they are not aligned properly.

But when I look at the Ford small block, the adapters necessary, and the Porsche transaxles, I don't see any comments on how they are aligned. I can't imagine you just bolt them together and hope.

I am not fully versed in the way things are done by Porsche. Maybe there's a secret in the way they design and build the transaxle.

Does anyone have comments on the procedure to do this, maybe a link to a Porsche service manual?

I understand how the stack-up of tolerances can affect a manufacturer and how you may need to adjust to eliminate or minimize them. But when you multiply the tolerance stack of three different manufacturers, there is no way just 'bolt it together' works. Yet I don't see any discussion on this. Any links?

Thanks

Paul
 

Brian Kissel

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Excellent topic Paul. I was able to help BryanF with his ZF alignment issue, but as you state 3 manufacturers. I am going to have the same issue when I do mine. A Brodix block, RCR adapter plate and a Ford Ricardo. My thoughts are to indicate the adapter plate to the crank centerline and then indicate the input on the Ricardo in. On Bryan’s I made a step hand reamer . If I remember correctly it stepped.007 in diameter every.485 in depth. Several people indicated you can just hog them out to .500 and hammer Chevy pins in. I made him some hardened offset dowels to boot. If I remember correctly he got it down to.0015. There is a write up on here by Bryan about the process and others chimed in as well. I’ll be watching this thread with interest. I have the Ricardo, just no engine or adapter plate.

Regards Brian
 

Paul Proefrock

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For those using transaxles that come with a bellhousing, you can indicate the adapter plate and then again indicate the bellhousing (the adapter plate may be redundant, but closer is better)

But those using transaxles with a one-piece case (ie, Porsche), and ideas on how to do them?
 

Darius Rudis

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Not sure of your question. My Porsche 996 trans and SBF, has RCR adapter plate. Alignment was measured trans-to-adapter, and then adapter-to-block. Could not stack and measure all at once (bellhousing/adapter/crank).
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Mark H.

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I just did this very thing, Ford to Porsche G86. As stated above aligned the adapter to the block. I like to use the allen type offset dowels, easy to rotate. Prior to dialing in I drill and tap the block for a set screw to hold the alignment dowel in place.You could use a roll or split pin to lock in place . Then do the same with the adapter to transaxle. Had .020 combined when I started, mostly between the block and adapter. The Kennedy adapter to trans was about .003 out. I got to near zero runout total on both, the transaxle slid right into place. The believe the Porsche input is on tapered roller bearings, so the input has no radial movement. I was used to dealing with Borg Warner and Ford top loader 4speeds with ball bearings which have some radial movement and a somewhat loose bronze bushing pilot. Using a bearing pilot bearing leaves very little room for error.
 
My personnal experience : I had to assemble small bloc Ford with a Ford top loader on a mustang, big bloc Ford Galaxie with a Ford top loader, and recently Dart SBF on the RCR GT40 with a ZF25. In all cases I never had problem of alignment. In all cases the bell housing is positionned by 2 studs on both side of the engine bloc. In the case of the Mustang and the Galaxie I used a bronze bearing to center the gear box before to srew it in place. Of course you have to be sure that both flanges of the bell housing are parallel.
In the case of the RCR GT40, I did not used the 2 bolts coming from inside the bell housing into the gear box, because if you use it not adjustement between the elements will be possible. I first mounted the bell housing using the 2 studs and bolt it in place, then I only used the 4 bolt of the ZF to bolt it in place on the engine. Then I added the 2 top bolts in the aluminum rail. And if you are align when you assemble it is going smoothly.
 

Mark H.

Supporter
Hi Jean, Did you check with a dail indicator to make sure the input shaft is not out of line with pilot bushing? Most usually are not aligned and you end up with a blown disc, chatter, hard shifts or worn input shaft bearing and blocker rings. Aftermarket blocks and bell housings are usually much worse than original Ford. You may can get it all to bolt in but usually the input shaft will be taking an elliptical path unbeknownst until disassembly. The only sure way is to locate is to measure. You may have lucked out and all is within tolerance on you builds. As I said top loaders with bronze pilots are forgiving.
 
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