1975 Rear Diff Rebuilds
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Joined: Apr 2024
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1975 Rear Diff Rebuilds
I live in Simi Valley CA, can anyone recommend a shop? Cost? Its a 4 speed.
I read the Zip does it also for $700, has anyone done that? How did it work? Not sure I want to pull the diff off myself. Never done it before. Is it complicated?
Or is it easier to just buy a rebuilt diff and install it?
I read the Zip does it also for $700, has anyone done that? How did it work? Not sure I want to pull the diff off myself. Never done it before. Is it complicated?
Or is it easier to just buy a rebuilt diff and install it?
NCM Grand Opening Veteran
Joined: Sep 2005
Posts: 20,979
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From: South of giving a damn
St. Jude Donor '11, '17
It's easier to buy a rebuild and install it, but it's going to be a crap shoot as to whether or not it's worth a damn. I'd be guessing not. Best bet is to send it to Gary @GTR1999 , but I don't know his backlog. Needless to say you'd be without your '75 for the short-term. You'd think there would be someone there that could do a quality job, but the cars are 50 years old now and not a huge demand, numbers wise.
Drifting
Joined: Sep 2016
Posts: 1,492
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From: Ventura California
Bairs does them for $895.
I wonder if that's who Zip sends them to.
If you are willing to drive to Ojai, I have a gentleman that has been rebuilding rear ends almost his entire life and he's 80.
He actually had a shop on the Ventura Avenue that specialized in rear ends.
He's rebuilding a couple of mine.
PM me if interested. I can ask Mump (his name) if he would do it for you. Certainly cheaper than shipping it to Zip and paying them $700
I wonder if that's who Zip sends them to.
If you are willing to drive to Ojai, I have a gentleman that has been rebuilding rear ends almost his entire life and he's 80.
He actually had a shop on the Ventura Avenue that specialized in rear ends.
He's rebuilding a couple of mine.
PM me if interested. I can ask Mump (his name) if he would do it for you. Certainly cheaper than shipping it to Zip and paying them $700
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Good to know thank you! I talked to Anthony at Hooper Rear Ends in Sun Valley (Really nice and seems very knowledgeable) , he said it would be $900 also, but I would have to bring the diff to him.
He said that if the rear end has some camber it could be the suspension pushing on the half shafts I think he said, which could cause the issue. So basically the whole rear end might need to be gone through, bushings, half shafts etc.
I told him the rear doesn't seem to have any camber, but it has some clunky sound when going slow in reverse and in first gear. He told me to try and change the rear diff fluid and add Friction Modifier XL3 which is a ford product. He said don't use the Chevy stuff. He said that might fix the issue and save me $900+. After researching the XL3, it did fix similar issues I am having.
Called the local Ford dealer, they have it. So going to pick that up with some gear oil and a lubricant suction gun after work and give it a shot. Fingers crossed!!!
He said that if the rear end has some camber it could be the suspension pushing on the half shafts I think he said, which could cause the issue. So basically the whole rear end might need to be gone through, bushings, half shafts etc.
I told him the rear doesn't seem to have any camber, but it has some clunky sound when going slow in reverse and in first gear. He told me to try and change the rear diff fluid and add Friction Modifier XL3 which is a ford product. He said don't use the Chevy stuff. He said that might fix the issue and save me $900+. After researching the XL3, it did fix similar issues I am having.
Called the local Ford dealer, they have it. So going to pick that up with some gear oil and a lubricant suction gun after work and give it a shot. Fingers crossed!!!
Le Mans Master
Joined: Nov 2001
Posts: 8,799
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From: LONG ISLAND
2025 C3 ('68-'73) of the Year Finalist - Unmodified
2024 C3 of the Year Finalist - Unmodified
2023 C3 of the Year Finalist - Unmodified
Tech Contributor
Joined: Aug 1999
Posts: 15,175
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From: Connecticut, USA
You are price shopping, big mistake- in my opinion. Instead of asking how much. Ask
Good luck.
- What is done to the diff?
- Is it built to application? if so how.
- What parts do you use- a kit from any supplier, NAPA, etc
- What is checked in the diff?
- Are new gears part of the build? if so what brand, are there any better than the others or will the cheapest gear set I find on ebay be the same?
- What is gear break in?
- Are there different type of parts- like axles, bearings, etc
- Do you rebuild the posi, do you know what posi is in it and what parts are used?
- Is there anything to be checked or done to a posi?
- Are there clutches in the posi and what type? If there is more than one type which one do you use and why?
- Are any special procedures needed to build the diff or are you just looking at the GM overhaul manual?
- What is tuning a posi or polishing a posi?
- Should there be any endplay in the axles, if so how much? Is there such a thing as too much or not enough?
- Are you a racer?
- How much time do you expect it to take and do you flat rate the labor or charge per hour? at what rate.
- How much abuse will the diff handle when you're done, do you warranty anything? as I leave your shop I will light up the tires and see.
Good luck.
Le Mans Master
Joined: Nov 2001
Posts: 8,799
Likes: 1,942
From: LONG ISLAND
2025 C3 ('68-'73) of the Year Finalist - Unmodified
2024 C3 of the Year Finalist - Unmodified
2023 C3 of the Year Finalist - Unmodified
You are price shopping, big mistake- in my opinion. Instead of asking how much. Ask
Good luck.
- What is done to the diff?
- Is it built to application? if so how.
- What parts do you use- a kit from any supplier, NAPA, etc
- What is checked in the diff?
- Are new gears part of the build? if so what brand, are there any better than the others or will the cheapest gear set I find on ebay be the same?
- What is gear break in?
- Are there different type of parts- like axles, bearings, etc
- Do you rebuild the posi, do you know what posi is in it and what parts are used?
- Is there anything to be checked or done to a posi?
- Are there clutches in the posi and what type? If there is more than one type which one do you use and why?
- Are any special procedures needed to build the diff or are you just looking at the GM overhaul manual?
- What is tuning a posi or polishing a posi?
- Should there be any endplay in the axles, if so how much? Is there such a thing as too much or not enough?
- Are you a racer?
- How much time do you expect it to take and do you flat rate the labor or charge per hour? at what rate.
- How much abuse will the diff handle when you're done, do you warranty anything? as I leave your shop I will light up the tires and see.
Good luck.
AND......................there ya go / from the TUSHY gooooh rooooh himself !!
Thread Starter
Advanced
Joined: Apr 2024
Posts: 67
Likes: 34
You are price shopping, big mistake- in my opinion. Instead of asking how much. Ask
Good luck.
- What is done to the diff?
- Is it built to application? if so how.
- What parts do you use- a kit from any supplier, NAPA, etc
- What is checked in the diff?
- Are new gears part of the build? if so what brand, are there any better than the others or will the cheapest gear set I find on ebay be the same?
- What is gear break in?
- Are there different type of parts- like axles, bearings, etc
- Do you rebuild the posi, do you know what posi is in it and what parts are used?
- Is there anything to be checked or done to a posi?
- Are there clutches in the posi and what type? If there is more than one type which one do you use and why?
- Are any special procedures needed to build the diff or are you just looking at the GM overhaul manual?
- What is tuning a posi or polishing a posi?
- Should there be any endplay in the axles, if so how much? Is there such a thing as too much or not enough?
- Are you a racer?
- How much time do you expect it to take and do you flat rate the labor or charge per hour? at what rate.
- How much abuse will the diff handle when you're done, do you warranty anything? as I leave your shop I will light up the tires and see.
Good luck.
Great information, thank you! I drained and refilled the fluid last night and added some friction modifier, took it for a spin, did some figure eights to get the fluid moved around and didn't feel any of the clunking I did before when going in reverse or in first gear at very low speeds. Fingers crossed. If it comes back or I guess is still there I will definitely take your advise!
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