Problem installing new poly mounts - The 1947 - Present Chevrolet & GMC Truck Message Board Network

HeavyK20 · 04-21-2004, 08:20 AM

The problem is when I install the new mounts the body sits on the front and back pads and there is a 3/4" air gap on the middle pads. If I remove the core support pads the cab will sit on all 4 cab pads but the core support rests on the frame.

Anyone else have this problem? Is there any body adjustments that would correct this? Any suggestions would be appreciated.

Eric

P.S. The truck is a K20.

**JIMs70GMC** · 04-21-2004, 08:35 AM

Eric, I've replace the mounts on both my trucks and the cab/front core support rested fine. Could your frame have a saddle in it, slight bend? I'm going to ask this next question not implying anything, you don't have the front and middle mounts reversed do you, as I believe the fronts are thinner than the middle? I have some pics of mine(70 GMC) in the link in my sig.

HeavyK20 · 04-21-2004, 08:48 AM

Yes, I have the thicker pad in the middle. I will have to check the frame for straightness.

It doesn't look like the fenders can be adjusted that much without throwing off the gap between the fender and door.

Dean · 04-21-2004, 09:15 AM

I never had any problem installing the poly mounts, but I have had some of them split and disentigrate over the years. I can take pics of my blue K20 with poly mounts if needed.

HeavyK20 · 04-21-2004, 09:57 AM

JIMs70GMC, I looked at your pics. I have Energy Suspension pads, and it looks like you have Prothane. I think my rear pad is taller and my front cab pad is shorter than than yours. That could be causing my problem.

Could you measure the height of your front and rear cab pads when you get a chance?

**JIMs70GMC** · 04-21-2004, 10:49 AM

Sounds like you got the 1/2ton 2wd mounts, they are different from the 3/4 ton 2wd and all 4wd mounts.

Sure will when I get home(around 2). I'll also take more pics.

**JIMs70GMC** · 04-21-2004, 09:38 PM

1

**JIMs70GMC** · 04-21-2004, 09:38 PM

2

**JIMs70GMC** · 04-21-2004, 09:40 PM

3 On the mid mount I did add some shims, about 1/4" total (2 extra washers). Pic are on the 70 C20/K20

**JIMs70GMC** · 04-21-2004, 09:41 PM

4

**JIMs70GMC** · 04-21-2004, 09:42 PM

5

**JIMs70GMC** · 04-21-2004, 09:42 PM

6

**Canadian694x4** · 04-22-2004, 01:12 AM

Hey Jim, those are Poly Mounts on your trucks? Do you recomend them over the Rubber Mounts? Where'd you get your's? Oh, and what type of washer's did you use to shim?

Do you have any updated Progress pics of the 70/71 K20?

Sorry about the 20 question's. I'm possibly doing my mounts soon and don't want to run into any probs like HeavyK20 is etc.

Thanks

Brian

Longhorn Man · 04-22-2004, 01:20 AM

You have the wrong mounts. Like said, the 2 wheel drive 1/2 ton has one p/n, and all others have the other p/n.

**JIMs70GMC** · 04-22-2004, 06:37 AM

Yep, Prothane Poly have the same kit on both trucks. The kit comes with all the washers. But I had to shim up the front cab mount on the 70/71 about 1/4" I went to the hardware store and bought washers for a 1 1/2" bolt, outside diameter 3" for the shims. When i put my poly kit on the fenders were off and I had to test fit them until I got the right number of "shims".
The prothane kit comes with rear mount replacement bolts. I ordered new bolts from LMC for the rad sup mount and front cab mount. The only probelm I had with the prothane kits is the front cab mount is a 9/16" bolt and the holes in the supplied washers is 1/2" so drilled them out.
The only thing I ever bought from energy suspension and they sent me the wrong item. I ordered new bushings for my stock springs and they sent me a bushing kit for lift springs, they did make it right though, but it sucks when the springs are off and can't put them back on for a couple days.

HeavyK20 · 04-22-2004, 08:16 AM

Thanks Guys, I have an email into Energy Suspension to find out what is going on whith these mounts. If it turns out that I have the correct mounts I am going to shim the front cab mount like JIMs70GMC did.

MOTHERTRUCKERS · 04-22-2004, 08:32 AM

Keep a close eye on your cab supports after driving awhile for any signs of crushing, poly body mounts are hard on cab supports.

**CUSTOM/10** · 04-22-2004, 09:51 AM

I had the same problem with my Energy Suspension Poly Mounts when I did mine. I didn't Have the time to contact them and figure it all out, so I made up two 1/2" thick rubber spacers to put on top of the front cab mounts. This was enough to correct the problem. I would like to hear what Energy Suspension has for an answer. ( By the way my truck is a 72 1/2 ton swb 4x4 ) Maybe I got the wrong mounts !!!

Gary

04-21-2004, 08:20 AM	#1
HeavyK20 Registered User Join Date: Dec 2001 Location: New Richmond, WI Posts: 547	Problem installing new poly mounts The problem is when I install the new mounts the body sits on the front and back pads and there is a 3/4" air gap on the middle pads. If I remove the core support pads the cab will sit on all 4 cab pads but the core support rests on the frame. Anyone else have this problem? Is there any body adjustments that would correct this? Any suggestions would be appreciated. Eric P.S. The truck is a K20. __________________ Eric 1969 K20, 465/205 package

04-21-2004, 08:35 AM	#2
JIMs70GMC user # 2756 Join Date: Jun 2001 Location: Chesapeake, Virginia Posts: 4,612	Eric, I've replace the mounts on both my trucks and the cab/front core support rested fine. Could your frame have a saddle in it, slight bend? I'm going to ask this next question not implying anything, you don't have the front and middle mounts reversed do you, as I believe the fronts are thinner than the middle? I have some pics of mine(70 GMC) in the link in my sig. __________________ 1970 K25, 8' stepside bed 350/465/205 44 up front, 60 in the rear 4.10s rolling on 33" Dunlop MTs 1986 K5, 350/465/208 Dana 60/14 bolt from a cucv 36" Super Swampers TSL/SX 1983 K20 w/ CUCV axles, 350/700R4/208 sitting on 37" Goodyears 1986 M1031 6.2 diesel, TH400/NP205 locker in the rear and a LS in the front, all stock for now..... 1986 K30, 350/400/205 dana 60 and 14 bolt. I kept the drivetrain. Body/bad and chassis are gone. 1981 K30, 350/465/205 dana 60 and dually 14 bolt. Has a G80, and a flat bed. Going to replace the flat bed. 1985 K20, 350/400/208 10 bolt and SF 14 bolt. I wonder where I can find some 1 tons. Hmmmmm

04-21-2004, 08:48 AM	#3
HeavyK20 Registered User Join Date: Dec 2001 Location: New Richmond, WI Posts: 547	Yes, I have the thicker pad in the middle. I will have to check the frame for straightness. It doesn't look like the fenders can be adjusted that much without throwing off the gap between the fender and door. __________________ Eric 1969 K20, 465/205 package

04-21-2004, 09:57 AM	#5
HeavyK20 Registered User Join Date: Dec 2001 Location: New Richmond, WI Posts: 547	JIMs70GMC, I looked at your pics. I have Energy Suspension pads, and it looks like you have Prothane. I think my rear pad is taller and my front cab pad is shorter than than yours. That could be causing my problem. Could you measure the height of your front and rear cab pads when you get a chance? __________________ Eric 1969 K20, 465/205 package

04-21-2004, 10:49 AM	#6
JIMs70GMC user # 2756 Join Date: Jun 2001 Location: Chesapeake, Virginia Posts: 4,612	Sounds like you got the 1/2ton 2wd mounts, they are different from the 3/4 ton 2wd and all 4wd mounts. Sure will when I get home(around 2). I'll also take more pics. __________________ 1970 K25, 8' stepside bed 350/465/205 44 up front, 60 in the rear 4.10s rolling on 33" Dunlop MTs 1986 K5, 350/465/208 Dana 60/14 bolt from a cucv 36" Super Swampers TSL/SX 1983 K20 w/ CUCV axles, 350/700R4/208 sitting on 37" Goodyears 1986 M1031 6.2 diesel, TH400/NP205 locker in the rear and a LS in the front, all stock for now..... 1986 K30, 350/400/205 dana 60 and 14 bolt. I kept the drivetrain. Body/bad and chassis are gone. 1981 K30, 350/465/205 dana 60 and dually 14 bolt. Has a G80, and a flat bed. Going to replace the flat bed. 1985 K20, 350/400/208 10 bolt and SF 14 bolt. I wonder where I can find some 1 tons. Hmmmmm

04-21-2004, 09:15 AM	#4
Dean Senior Member Join Date: Jan 2000 Location: Cincinnati, Ohio Posts: 1,492	I never had any problem installing the poly mounts, but I have had some of them split and disentigrate over the years. I can take pics of my blue K20 with poly mounts if needed.

04-21-2004, 09:38 PM	#7
JIMs70GMC user # 2756 Join Date: Jun 2001 Location: Chesapeake, Virginia Posts: 4,612	pics 1 __________________ 1970 K25, 8' stepside bed 350/465/205 44 up front, 60 in the rear 4.10s rolling on 33" Dunlop MTs 1986 K5, 350/465/208 Dana 60/14 bolt from a cucv 36" Super Swampers TSL/SX 1983 K20 w/ CUCV axles, 350/700R4/208 sitting on 37" Goodyears 1986 M1031 6.2 diesel, TH400/NP205 locker in the rear and a LS in the front, all stock for now..... 1986 K30, 350/400/205 dana 60 and 14 bolt. I kept the drivetrain. Body/bad and chassis are gone. 1981 K30, 350/465/205 dana 60 and dually 14 bolt. Has a G80, and a flat bed. Going to replace the flat bed. 1985 K20, 350/400/208 10 bolt and SF 14 bolt. I wonder where I can find some 1 tons. Hmmmmm

04-21-2004, 09:38 PM	#8
JIMs70GMC user # 2756 Join Date: Jun 2001 Location: Chesapeake, Virginia Posts: 4,612	2 2 __________________ 1970 K25, 8' stepside bed 350/465/205 44 up front, 60 in the rear 4.10s rolling on 33" Dunlop MTs 1986 K5, 350/465/208 Dana 60/14 bolt from a cucv 36" Super Swampers TSL/SX 1983 K20 w/ CUCV axles, 350/700R4/208 sitting on 37" Goodyears 1986 M1031 6.2 diesel, TH400/NP205 locker in the rear and a LS in the front, all stock for now..... 1986 K30, 350/400/205 dana 60 and 14 bolt. I kept the drivetrain. Body/bad and chassis are gone. 1981 K30, 350/465/205 dana 60 and dually 14 bolt. Has a G80, and a flat bed. Going to replace the flat bed. 1985 K20, 350/400/208 10 bolt and SF 14 bolt. I wonder where I can find some 1 tons. Hmmmmm

04-21-2004, 09:40 PM	#9
JIMs70GMC user # 2756 Join Date: Jun 2001 Location: Chesapeake, Virginia Posts: 4,612	3 3 On the mid mount I did add some shims, about 1/4" total (2 extra washers). Pic are on the 70 C20/K20 __________________ 1970 K25, 8' stepside bed 350/465/205 44 up front, 60 in the rear 4.10s rolling on 33" Dunlop MTs 1986 K5, 350/465/208 Dana 60/14 bolt from a cucv 36" Super Swampers TSL/SX 1983 K20 w/ CUCV axles, 350/700R4/208 sitting on 37" Goodyears 1986 M1031 6.2 diesel, TH400/NP205 locker in the rear and a LS in the front, all stock for now..... 1986 K30, 350/400/205 dana 60 and 14 bolt. I kept the drivetrain. Body/bad and chassis are gone. 1981 K30, 350/465/205 dana 60 and dually 14 bolt. Has a G80, and a flat bed. Going to replace the flat bed. 1985 K20, 350/400/208 10 bolt and SF 14 bolt. I wonder where I can find some 1 tons. Hmmmmm

04-21-2004, 09:41 PM	#10
JIMs70GMC user # 2756 Join Date: Jun 2001 Location: Chesapeake, Virginia Posts: 4,612	4 4 __________________ 1970 K25, 8' stepside bed 350/465/205 44 up front, 60 in the rear 4.10s rolling on 33" Dunlop MTs 1986 K5, 350/465/208 Dana 60/14 bolt from a cucv 36" Super Swampers TSL/SX 1983 K20 w/ CUCV axles, 350/700R4/208 sitting on 37" Goodyears 1986 M1031 6.2 diesel, TH400/NP205 locker in the rear and a LS in the front, all stock for now..... 1986 K30, 350/400/205 dana 60 and 14 bolt. I kept the drivetrain. Body/bad and chassis are gone. 1981 K30, 350/465/205 dana 60 and dually 14 bolt. Has a G80, and a flat bed. Going to replace the flat bed. 1985 K20, 350/400/208 10 bolt and SF 14 bolt. I wonder where I can find some 1 tons. Hmmmmm

04-21-2004, 09:42 PM	#11
JIMs70GMC user # 2756 Join Date: Jun 2001 Location: Chesapeake, Virginia Posts: 4,612	5 5 __________________ 1970 K25, 8' stepside bed 350/465/205 44 up front, 60 in the rear 4.10s rolling on 33" Dunlop MTs 1986 K5, 350/465/208 Dana 60/14 bolt from a cucv 36" Super Swampers TSL/SX 1983 K20 w/ CUCV axles, 350/700R4/208 sitting on 37" Goodyears 1986 M1031 6.2 diesel, TH400/NP205 locker in the rear and a LS in the front, all stock for now..... 1986 K30, 350/400/205 dana 60 and 14 bolt. I kept the drivetrain. Body/bad and chassis are gone. 1981 K30, 350/465/205 dana 60 and dually 14 bolt. Has a G80, and a flat bed. Going to replace the flat bed. 1985 K20, 350/400/208 10 bolt and SF 14 bolt. I wonder where I can find some 1 tons. Hmmmmm

04-21-2004, 09:42 PM	#12
JIMs70GMC user # 2756 Join Date: Jun 2001 Location: Chesapeake, Virginia Posts: 4,612	6 6 __________________ 1970 K25, 8' stepside bed 350/465/205 44 up front, 60 in the rear 4.10s rolling on 33" Dunlop MTs 1986 K5, 350/465/208 Dana 60/14 bolt from a cucv 36" Super Swampers TSL/SX 1983 K20 w/ CUCV axles, 350/700R4/208 sitting on 37" Goodyears 1986 M1031 6.2 diesel, TH400/NP205 locker in the rear and a LS in the front, all stock for now..... 1986 K30, 350/400/205 dana 60 and 14 bolt. I kept the drivetrain. Body/bad and chassis are gone. 1981 K30, 350/465/205 dana 60 and dually 14 bolt. Has a G80, and a flat bed. Going to replace the flat bed. 1985 K20, 350/400/208 10 bolt and SF 14 bolt. I wonder where I can find some 1 tons. Hmmmmm

04-22-2004, 01:12 AM	#13
Canadian694x4 Born To Lose Club Join Date: Feb 2003 Location: Calgary, Alberta/Oxenden, Ontario, Great White North Posts: 13,306	Hey Jim, those are Poly Mounts on your trucks? Do you recomend them over the Rubber Mounts? Where'd you get your's? Oh, and what type of washer's did you use to shim? Do you have any updated Progress pics of the 70/71 K20? Sorry about the 20 question's. I'm possibly doing my mounts soon and don't want to run into any probs like HeavyK20 is etc. Thanks Brian __________________ Brian Smith - "Born To Lose" 1969 Chevrolet K10 LWB Fleetside - Proud Owner For 20 Yrs - 1 of 208 Built & Sold In Canada! - 283 V8/350TH/NP208, 2" All Spring Lift, 32" Good Year MT/R's. 1972 GMC K2500 Custom LWB Fleetside - Proud Owner For 2 Yrs - 1 of 571 Built & Sold In Canada! - 350 V8/SM465/NP205, 4” Rough Country Lift, 33” Interco TSL Thornbirds 2007.5 GMC Sierra SLE 2500HD 4x4 - Proud Owner For 15 Yrs - 6.6L V8 Duramax Diesel/Allison 1000, 2" Lift, 33" Mickey Thompson MTZ's. 2008 Yamaha Raptor 700r - Proud Owner For 13 Yrs - ITP Mud Lites. 2015 John Deere 1025R - Proud Owner For 6 Yrs - 24HP Diesel/H120/54D/260B/SB1154. Last edited by Canadian694x4; 04-22-2004 at 01:23 AM.

04-22-2004, 01:20 AM	#14
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	You have the wrong mounts. Like said, the 2 wheel drive 1/2 ton has one p/n, and all others have the other p/n.

04-22-2004, 06:37 AM	#15
JIMs70GMC user # 2756 Join Date: Jun 2001 Location: Chesapeake, Virginia Posts: 4,612	Yep, Prothane Poly have the same kit on both trucks. The kit comes with all the washers. But I had to shim up the front cab mount on the 70/71 about 1/4" I went to the hardware store and bought washers for a 1 1/2" bolt, outside diameter 3" for the shims. When i put my poly kit on the fenders were off and I had to test fit them until I got the right number of "shims". The prothane kit comes with rear mount replacement bolts. I ordered new bolts from LMC for the rad sup mount and front cab mount. The only probelm I had with the prothane kits is the front cab mount is a 9/16" bolt and the holes in the supplied washers is 1/2" so drilled them out. The only thing I ever bought from energy suspension and they sent me the wrong item. I ordered new bushings for my stock springs and they sent me a bushing kit for lift springs, they did make it right though, but it sucks when the springs are off and can't put them back on for a couple days. __________________ 1970 K25, 8' stepside bed 350/465/205 44 up front, 60 in the rear 4.10s rolling on 33" Dunlop MTs 1986 K5, 350/465/208 Dana 60/14 bolt from a cucv 36" Super Swampers TSL/SX 1983 K20 w/ CUCV axles, 350/700R4/208 sitting on 37" Goodyears 1986 M1031 6.2 diesel, TH400/NP205 locker in the rear and a LS in the front, all stock for now..... 1986 K30, 350/400/205 dana 60 and 14 bolt. I kept the drivetrain. Body/bad and chassis are gone. 1981 K30, 350/465/205 dana 60 and dually 14 bolt. Has a G80, and a flat bed. Going to replace the flat bed. 1985 K20, 350/400/208 10 bolt and SF 14 bolt. I wonder where I can find some 1 tons. Hmmmmm



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04-22-2004, 08:16 AM	#16
HeavyK20 Registered User Join Date: Dec 2001 Location: New Richmond, WI Posts: 547	Thanks Guys, I have an email into Energy Suspension to find out what is going on whith these mounts. If it turns out that I have the correct mounts I am going to shim the front cab mount like JIMs70GMC did. __________________ Eric 1969 K20, 465/205 package

04-22-2004, 08:32 AM	#17
MOTHERTRUCKERS Registered User Join Date: Dec 1999 Location: BRADENTON FLA Posts: 3,269	Keep a close eye on your cab supports after driving awhile for any signs of crushing, poly body mounts are hard on cab supports. __________________ Rest in Peace Ed. Thanks for all the good times.

04-22-2004, 09:51 AM	#18
CUSTOM/10 Senior Member Join Date: May 2003 Location: Sandown, NH Posts: 2,810	Energy Suspension Poly Mounts I had the same problem with my Energy Suspension Poly Mounts when I did mine. I didn't Have the time to contact them and figure it all out, so I made up two 1/2" thick rubber spacers to put on top of the front cab mounts. This was enough to correct the problem. I would like to hear what Energy Suspension has for an answer. ( By the way my truck is a 72 1/2 ton swb 4x4 ) Maybe I got the wrong mounts !!! Gary

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