Motor swap - axle C-line alignment (Page 1/1)
Wichita APR 29, 10:08 AM
I'm in the prepping stage of doing an engine swap, now that winter hibernation is over.

Also, my original plans of a swap has changed from keeping the original transmission, but now I have something much better for the swap and will not be using the original Isuzu transmission.

I went ahead and put the 5-speed Isuzu back on the cradle, original axles and everything else, just to see how things will need to be lined up and take measurements for axles, motor mounts and etc. vs the original stock configuration. Since I won't be using the the original transmission, I need to carefully plan on how the new motor/transmission will line up.



I really need a reference from others who have done swaps on axle centerline dimensions, both forwards/aft and also a height reference. This is to double-check myself, so that I'm overlooking anything or using the wrong reference points.

I combed through the forum to find some information and only came across an archived one with Archie explaining a bit of it with measuring engine bay for motor fit. He had a reference point of using the cradle's forward mounting bolt. It didn't have a height reference though. Yes, I'll be using the original 14" wheels, so I won't be putting on any aftermarket wheels.
https://www.fiero.nl/forum/...090219-2-088120.html




Cradle dimension is somewhat helpful, but doesn't show exactly where the axle centerline is.



Any help with this would be greatly appreciated.

[This message has been edited by Wichita (edited 04-29-2022).]

olejoedad APR 29, 10:40 AM
What trans are you going to be using?

Put the driver side axle seal in the same location as the Isuzu axle seal. You can lower it some if you want to, it won't hurt a thing.
Wichita APR 29, 11:46 AM

quote
Originally posted by olejoedad:

What trans are you going to be using?

Put the driver side axle seal in the same location as the Isuzu axle seal. You can lower it some if you want to, it won't hurt a thing.



This is this motor / transmission I'm putting in. This picture was snagged of the internet, but it is the exact one I'm using. I haven't taken a picture of the one I have, but I have one on a pallet and wrapped in a tarp, so I haven't gotten around to take any pictures of it.
fieroguru APR 30, 08:44 AM
When it comes to axles and CVs, you can be +/- 2" in placement (up/down, forward/back) vs. stock w/o having any issues. The usable axle angle on CVs is in the double digits, no need to keep them under 5 degrees. Generally speaking if the engine fits, nothing hits, and nothing binds, it is hard to have too large of a CV axle angle within the stock Fiero engine bay

The most important thing is to check for binding at all extremes of suspension movement (remove springs and cycle full droop/full compression while turning the axle by hand). Binding will break the axles and transmission.
Wichita APR 30, 10:14 AM

quote
Originally posted by fieroguru:

When it comes to axles and CVs, you can be +/- 2" in placement (up/down, forward/back) vs. stock w/o having any issues. The usable axle angle on CVs is in the double digits, no need to keep them under 5 degrees. Generally speaking if the engine fits, nothing hits, and nothing binds, it is hard to have too large of a CV axle angle within the stock Fiero engine bay

The most important thing is to check for binding at all extremes of suspension movement (remove springs and cycle full droop/full compression while turning the axle by hand). Binding will break the axles and transmission.



This is very helpful. I was thinking that there was a smaller tolerance than 2", I was figuring it was more like a 1/4" at max. Since I have to come up with custom axles, I just need to take special care in how they will fit length wise as well.
fieroguru APR 30, 10:47 AM
When you start comparing the axle locations between the various transmissions installed in Fieros, you will find there is over 1" variation with the engine in the exact same location.

Also...
Lower the car 2" and the axle angle changes 2" this is done quite often w/o issue.

Many swappers lower the drivetrain up to 1" (clearance issues limit going lower) w/o issue.

Some of us have done both and saw a 3" axle change and put 60k miles on the swap w/o issue.