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Author Topic: Diff and subframe damage. What advice?
Kyle Burkhardt
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My 99 got rearended in the last race of the season. Everything looked cosmetic until I got the exhaust out of the way and found this mess. I think the subframe damage is just cosmetic. What can I do to save this diff--its the original with only 15k miles?

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Kyle Burkhardt
NASA Midwest
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tyler raatz
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The diff is a pretty easy fix, v-notch around the crack and have a good welder tig it back together. Small reinforcment plates can be welded into the hollowed out area to strengthen the welded area.

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We have diff housings and subframes, they are relatively inexpensive. It is not "legal" to brace the diff housing, but it would be a weeny protest. By the time you pay to have welded you can have a complete used one.

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Jim

[ 12-24-2010, 09:39 PM: Message edited by: Drago ]

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Jim Drago
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Kyle Burkhardt
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What's involved in transferring the guts into the new housing? Can it be done by a guy who's never even changed the fluid in a diff by himself?

Does the force needed to break that arm necessarily tweak the subframe?

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Kyle Burkhardt
NASA Midwest
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The case is very simple. Just unbolt the bolts around the perimeter, use a bead of silcone on the replacemnet and it drops in.
Typically the force does not bend subframe, but I see yours is bent in the picture by the sway bar.

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Jim Drago
East Street Auto Salvage
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Kyle Burkhardt
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I haven't been able to find a DIY on R/R the diff. Anyone have a link to one?

The subframe damage looks cosmetic. Caused by the folds in the body hitting it. SWay bar was untouched.

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Kyle Burkhardt
NASA Midwest
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Before attacking the diff, I would check the subframe for bends. No sense in pulling the diff to replace the housing, only to have a bent subframe that will require pulling the diff a second time.

I sell an inexpensive tool for checking the rear subframe for bends.

Sway bars very rarely get damaged, but subframe bend regularly.

Dave

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Kyle Burkhardt
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If I transfer to the diff to the new housing, does that require any kind of adjument or reassembly, or does it just all come out of one and into the other together?

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Kyle Burkhardt
NASA Midwest
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Dave Stevens
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Miata.net has some good tutorials. A swap isn't difficult with moderate mechanical ability. It's the gear change that's tough if you've never done it but if it's a straight swap you won't be taking the pumpkin apart. A big +1 on taking the rest of the subframe down before swapping the diff. If it cracked the diff like that and bent those other members there is a pretty good chance other parts are askew.

On edit, wrong link posted. It was the pinion swap and you don't want to try that alone the first time if you can help it.

Link to tutorial page where you might find something...

http://www.miata.net/garage/garageengine.html

Dave

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Kyle Burkhardt
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Thanks. I've been looking around miata.net and found what I need. Gonna get the diff down and then reevaluate. I think what happened is the car that hit me got a good shot on the exhaust and that worked as a lever to snap the diff.

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Kyle Burkhardt
NASA Midwest
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You should be able to remove the broken rear housing and bolt on a good one pretty quickly. No gear adjustment/shimming required. That notch in the ear of the aluminum rear housing is designed to break exactly where yours did. We went through 3-4 of them last season during soft to hard rear hits. All were welded back together and sit in reserve as spares.

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-Cy
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