OEM Trailer Hitch Receiver - Impact tightened by shop

SoCal Angler · June 18

After my recent rear end bumper damage, body shop has made the repairs and included a new OEM receiver hitch. I started thinking about how it was tightened...to specs or by hand or ??. I called the body shop and asked and they said it was tightened by an impact gun. I said I wanted it tightened to OEM specs. They said no problem, bring it to shop today and they will torque to specs, which they say is 74 ft/lbs.

A couple of questions,,,,

1. Should new bolts have been used? If so, how many are there (bill shows one and four (I assume different areas of receiver).

2., Since they torqued with impact gun and now are going to probably loosen and then torque to spces, will that damage/stretch the bolts?

3. If old bolts were reused (truck has 9000 miles), is that a problem?

4. Any other things iI may have missed with regard to receiver replacement?

NOTE: Attached are the receiver hitch specs from my digital OEM service manual. It shows to horizontal mounting bolts and four vertically mounted bolts. Other sections of manual reference eight vertical bolts.

Thanks!

Edited June 18 by SoCal Angler

newdude · June 18

38 minutes ago, SoCal Angler said:

After my recent rear end bumper damage, body shop has made the repairs and included a new OEM receiver hitch. I started thinking about how it was tightened...to specs or by hand or ??. I called the body shop and asked and they said it was tightened by an impact gun. I said I wanted it tightened to OEM specs. They said no problem, bring it to shop today and they will torque to specs, which they say is 74 ft/lbs.

A couple of questions,,,,

1. Should new bolts have been used? If so, how many are there (bill shows one and four (I assume different areas of receiver).

2., Since they torqued with impact gun and now are going to probably loosen and then torque to spces, will that damage/stretch the bolts?

3. If old bolts were reused (truck has 9000 miles), is that a problem?

4. Any other things iI may have missed with regard to receiver replacement?

NOTE: Attached are the receiver hitch specs from my digital OEM service manual. It shows to horizontal mounting bolts and four vertically mounted bolts. Other sections of manual reference eight vertical bolts.

Thanks!

4 vertical bolts. They are one time use torque to yield fasteners and should not be re-used.

Yes, they should be torqued to the proper spec.

SoCal Angler · June 18

Thanks newdude, that's what I thought. Since new bolts were used, can they retorque them without issue?

newdude · June 18

Just now, SoCal Angler said:

Thanks newdude, that's what I thought. Since new bolts were used, can they retorque them without issue?

No. If they were rammed in with an impact, they are stretched and need to be replaced.

Hence one time use torque to yield fasteners.

Another JR · June 18

Based on the service manual picture you posted, the four vertical bolts are single use and the torque specifications appear to be intended to be “torque to yield,” which permanently elongates the bolt. If they were torqued per that specification they should not be reused. However, if they used a properly limited impact device and only torqued them to the initial torque value of 89 ft lbs and did not do the final 70 to 80 degrees of additional rotation, they never yielded the bolts and they could be “reused” and torqued properly. The biggest issue in deciding whether to reuse them likely will be uncertainty over the torque applied by the impact driver.

Another JR · June 18

Newdude posted while I was typing. If they didn’t have very good torque control with their impact driver or if they did the final quarter turn after applying 89 ft lbs, I agree with him they should be replaced.

AndrewF · June 18

Stuff like this is why I have trust issues with anyone else working on my vehicles.

SoCal Angler · June 18

How difficult is it to access these six mounting bolts for torquing? I do not have a lift. I may want to replace and tighten the bolts myself to ensure it is done to proper specs. Since body shop did not do it properly to begin with, I’m not confident they will do it correctly with new bolts. Also, they claimed 74 ft lbs when that is not correct.

Also, seems odd that there are only 4 vertical bolts and two horizontal bolts..,, my ford f350 I believe had 6-8 vertical bolts.

Edited June 18 by SoCal Angler

Another JR · June 18

Is your truck not available for you to look? If not, can look at mine later this morning and post back. I suspect they are easily accessible.

SoCal Angler · June 18

Just visited the body shop. They agreed that the bolts are "torque to yield" bolts and will order and replace all six bolts (GM OEM).

They assured me that the tech will install using a torque wrench and and torque angle gauge.

The estimator is not too clear with OEM torque specs, finding different numbers. Are the specs listed on my attached pic correct? I also googled and found various specs. Not sure why they are not using OEM service manual. I will provide them with the print out and steps to follow when torquing.

Edited June 19 by SoCal Angler

newdude · June 18

3 minutes ago, SoCal Angler said:

Just visited the body shop. They agreed that the bolts are yield to torque bolts and will order and replace all six bolts.

They assured me that the tech will install using a torque wrench only.

The estimator is not too clear with c

OEM torque specs. Are the specs listed on my attached pic correct? I also googled and found various specs .

are not very clear with

torque

The one you posted is correct. Just the 4 bolts are one time use. The other two don't need to be replaced.

SoCal Angler · June 19

Thank you to all who were quick to respond; providing me with timely and correct info needed to get this correctly addressed today with the body shop. I will be providing this doc I created (with the help of AI) for them to follow. I made it as clear as possible.

Maybe they'll consider this disrespectful, but they did not perform the install correctly the first time. If they allow me to (which I do not believe it is allowed for liability and insurance requirements) I will bring the bolts home and replace myself.

Hitch install - Steps and torque specs.docxHitch install - Steps and torque specs.docx

Edited June 19 by SoCal Angler

Chuck FB · June 19

15 hours ago, SoCal Angler said:

Thank you to all who were quick to respond; providing me with timely and correct info needed to get this correctly addressed today with the body shop. I will be providing this doc I created (with the help of AI) for them to follow. I made it as clear as possible.

Maybe they'll consider this disrespectful, but they did not perform the install correctly the first time. If they allow me to (which I do not believe it is allowed for liability and insurance requirements) I will bring the bolts home and replace myself.

Hitch install - Steps and torque specs.docxHitch install - Steps and torque specs.docx 310.39 kB · 5 downloads

Great info to have, I printed out what you had in your document as well as Newdudes post as I could see this mistake with the hardware happening very often if not realizing what type of special bolts are being used and just guess on bolt size for torque or the good enough "easy" method as per whack in the used bolts with an impact and send it !.

carkhz316 · June 21

Its because they have thread locking compound on them. I would bet money that they are actually reusable and not a literal TTY bolt because GM and most other OEMs don't trust techs and the end-user to apply thread locker properly in the same way they don't trust anyone to solder properly (and instead instructing crimps everywhere). Torque To Angle =/ Torque To Yield.

If you think dealerships or any technician replaces every 'discard' bolt in every procedure, I have a bridge to sell you.

Edited June 21 by carkhz316

Another JR · June 21

15 hours ago, carkhz316 said:

Its because they have thread locking compound on them. I would bet money that they are actually reusable and not a literal TTY bolt because GM and most other OEMs don't trust techs and the end-user to apply thread locker properly in the same way they don't trust anyone to solder properly (and instead instructing crimps everywhere). Torque To Angle =/ Torque To Yield.

If you think dealerships or any technician replaces every 'discard' bolt in every procedure, I have a bridge to sell you.

I have had the same suspicion that some of these single use bolt installations are not actually torque to yield. In this case, the size involved and the initial torque, plus the additional rotation angle, don’t seem to be enough to be causing yield. However I have not done the actual calculations. One reason to use torque plus angle when not intending TTY is to reduce variation in the clamping force due to thread or head friction.

Edited June 22 by Another JR