rear axle being true

Transmission to Rear-end

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AMXstocker1
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rear axle being true

Post by AMXstocker1 » Fri Sep 08, 2017 2:10 pm

Has anyone had an axle make a car hard to push our amx weighs 3000lbs without a driver but if you go to roll the car it feels like your pushing a 5000lb truck and after some inspection it looks like the rear axle (chrysler 8 3/4)pulled some when the backbrace was welded on further evidence is the axles and bearings do not want to come in or out easily at all. now its already apart and at the chassis shop getting the ends cut off and rewelded on true with the mains on the center section. i'm curious if this could be worth some et how much i'm sure would depend on how far out it was. has anyone trued up an axle like this and found a significant difference?

RCJ
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Re: rear axle being true

Post by RCJ » Fri Sep 08, 2017 3:14 pm

When I was using a 9'' ford in my dirt track cars that was something that we checked often.It made a difference in how the car drove,I Would not be surprised to see a reduction in ET.

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Re: rear axle being true

Post by bigjoe1 » Sat Sep 09, 2017 1:50 pm

The way a car rolls when pushed by hand can make a big difference in the times going down the track. Every car that I have been involved with that pushes very easy, always runs faster than it should down the track. For instance, we run a 65 box Nova for drag racing. I have run customers engines in our car, and I have seen where our car is as much as FIVE MPH, and two to three tenths faster than there car, at almost the same weight-- It is a big deal




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AMXstocker1
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Re: rear axle being true

Post by AMXstocker1 » Sun Sep 10, 2017 12:16 am

Thanks for the reply thats inspiring i've been curious if that couldn't be something holding this combo back, i would like to see a big change.

Jeff Lee
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Re: rear axle being true

Post by Jeff Lee » Sun Sep 10, 2017 1:32 am

I run a Dana 60 in my AMX...from day 1. It is all MW components with MW adding CM axle tubes. I have never had a problem and yes, pushes easy. I have known cars without CM axle tubes and have seen enough to know even thick wall truck tubes can be a problem. With out CM tubes, and if you insist on running an 8 3/4 with it’s limited gear ratio availability, you need to run forward supports; like a strut arm, from the front side of the end to a bracket on the frame. FYI - Looking at everybody’s favorite, the 9”, you can build a far stronger Dana 60 which is much more efficient as well (9” is about 3% loss in power over a Dana 60!), for less money than a tricked out 9”. You can find good deals on used Dana’s in all sorts of widths.
Eventually I will be adding ceramic bearings to my Dana. And the front. It’s not horribly expensive.
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Re: rear axle being true

Post by sanfordandson » Sun Sep 10, 2017 2:45 pm

Even a 1/8 inch off in a dirt car makes a difference. We try to get them to 1/16 or less. I can see it affecting a drag car if off enough.

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Re: rear axle being true

Post by AMXstocker1 » Mon Sep 11, 2017 12:28 am

Jeff

i agree i would like to go dana 60 and this was a 12 second bracket car when we put the 8 3/4 under it in 99 and its just stayed there its got good axles in it but it had a backbrace that was not professionally welded on and its always been hard to push and now we know why, got a call from the chassis shop today tell me it was actually to far bent to cut and weld the ends back on straight. we have another housing that i had narrowed for my 70 amx so where taking that in and just going to have him move perches so it will fit my dads car, leaf springs have been moved in board on his and not mine but the axles are the same width and both 8 3/4 on purpose so we could move pumpkins inbetween the 2 cars, and i know this housing is true because it was narrowed properly with a jig and done right. anyway going dana 60 isn't in the cards at the moment i might go that way on my 70 since my housing just got donated to get my dads car back at the track.

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Re: rear axle being true

Post by Jeff Lee » Mon Sep 11, 2017 1:18 pm

Understandable....Even with a back brace I still suggest a forward CM strut bar with him ends. FYI - Calvert sells CM spring perches for around $100 a pair.
Glad you found the problem as fixing a bent car can’t be overstated!
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Re: rear axle being true

Post by Diodedog » Thu Sep 21, 2017 10:14 pm

I have a stock 65 B body 8 3/4 housing in my car and have checked it with bare wheels in the past but will check it again soon. I put the housing in back in 72 and have raced it ever since, it's a mid to high 10 second car at 3500lbs, I hope it is off, it'll be an inexpensive et gain. A car with a stock 727 will always be a bear to push, keep that in mind too.

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Re: rear axle being true

Post by turbo2256b » Fri Sep 22, 2017 10:41 am

Using dry ice and a torch straightened out a ford 9" hsg gained 2 tenths of a second in the quarter

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Re: rear axle being true

Post by AMXstocker1 » Fri Sep 22, 2017 10:45 am

We got the new housing in and the difference is remarkable its noticeably easier to push and the tires spin much more freely. with the old housing out and the new one side by side the amount our old one was bent was one of those how did we not see this moments. we are going to a race tomorrow and i'll report back on gains although its not a good aba test becuase when we swapped housings we also put in some 4.86s gears from the 4.56s that where in last race. the car responded so well to the 4.56s we figured we go ahead and try a 4.86 especially just running 1/8th mile in the 1/4 i think it would be spinning higher than i'd like for too long with the 4.86s.

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