Rough Reverse

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WilliamsWaggy
Posts: 6
Joined: Tue Oct 24, 2017 7:33 am

Rough Reverse

Post by WilliamsWaggy »

Hello. I need some help. My 88 GW has started idling rough, but ONLY in reverse gear. It is so weird. It fires up fine, idles smooth in neutral and drives without incident. However, when I shift to reverse, it starts vibrating rough, even as I am pressing the brake. When I give some gas, it shakes as I am reversing, but then does okay with a little momentum, but then when I shift to drive, does perfectly fine. I read it might be an engine mount issue, but it does not seem to be that to me. I would greatly appreciate your collective wisdom!
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Stuka
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Re: Rough Reverse

Post by Stuka »

Checking for engine mounts is easy.

Have the hood open with somebody looking at the engine from the side, NOT from in front, and then while pressing the brake pedal FIRMLY and the parking brake engaged, shift it to reverse. See if the engine torques over. Do the same drive. You can also apply a very small amount of throttle to see if it really moves.

The engine will move a small amount with good mounts, but with bad mounts, its normally pretty obvious that it moves more than it should.
2017 JKU Rubicon
Pevious Jeeps: 1981 J10, 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ

candymancan
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Re: Rough Reverse

Post by candymancan »

the transmission has a mount too. Honestly the mounts on these engines are flat solid blocks of rubber.. Unless they rotted comoletetly or the metal part rusted off i doubt engine mounts are bad.. They rarely go bad on these trucks.. Unlike those round hollow mounts on the newer grand cherokees
1998 Jeep Grand Cherokee 5.9L Limited 219k
1998 Jeep Grand Cherokee 4.0 I6 laredo 430k
1990 Jeep Grand Wagoneer 155k
1976 Jeep J10.. 85k(repaired)

KJ Ryu
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Re: Rough Reverse

Post by KJ Ryu »

candymancan wrote:the transmission has a mount too. Honestly the mounts on these engines are flat solid blocks of rubber.. Unless they rotted comoletetly or the metal part rusted off i doubt engine mounts are bad.. They rarely go bad on these trucks.. Unlike those round hollow mounts on the newer grand cherokees
You must be lucky. I've replaced engine and trans mounts in all three of the FSJs I've driven, usually one of the first things to get done. Polyurethane ones seem to be holding up pretty well.
Ron

2005 KJ, Hit-n-Run, 2am 6-17-2012, Totaled. :mad:
1977 SJ J10, 4v360, T18, D20, 37x14s, SOA & SF on tons, still ugly.
1978 SJ Wagoneer, 4v360, QT, 33x12.5s, lift by Sawzall :-bd NOT Running :(
1977 SJ J10, SniperEFI 401, QT, D44s, 31X10.5s :fsj:
2006 KJ
Mars wrote:One man's trans leak is another's penetrating oil :D
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HeavyMetalThunder_81
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Re: Rough Reverse

Post by HeavyMetalThunder_81 »

KJ Ryu wrote:
candymancan wrote:the transmission has a mount too. Honestly the mounts on these engines are flat solid blocks of rubber.. Unless they rotted comoletetly or the metal part rusted off i doubt engine mounts are bad.. They rarely go bad on these trucks.. Unlike those round hollow mounts on the newer grand cherokees
You must be lucky. I've replaced engine and trans mounts in all three of the FSJs I've driven, usually one of the first things to get done. Polyurethane ones seem to be holding up pretty well.
x2 I've had to replace torn engine mounts on almost every FSJ I've owned. Heck, I've had to replace my trans mount twice on the one I own now.
-Jonny B.
1979 Cherokee Golden Eagle - UNDER CONSTRUCTION
7" lift, 35x12.5x15
AMC 401 - Pro-FLo 4 FI
NV4500/NWFBB/NP205 - Triple Stick'd
F D44 - 4.10, Eaton E-Locker
R M23 - 4.10, Detroit Locker

1979 Cherokee Chief - Parts
1979 Cherokee Chief - Parts
1979 Wagoneer - Sold
1981 Cherokee Chief - Cubed

FSJ Guy
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Re: Rough Reverse

Post by FSJ Guy »

Put poly motor mounts on and never have to do the job again.

BJ's Offroad has a motor and tranny mount combo pack.
Ethan Brady

http://www.bigscaryjeep.com

Jeepless, but I still have a lots of old parts in my garage!

will e
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Re: Rough Reverse

Post by will e »

The downside of poly mounts is you will feel more engine vibration. It's a trade off.
81 Waggy 'WILL E' Retired
82 Cherokee WT - SOA/SF/high steer/Alcan springs/agr box/Borgeson steering shaft/AMC 401/performer/holley TA/HEI/BeCool/727/ALTAS (2.0/2.72/5.44)/D60 Snofighter(Yukon Zip,hubs,stubs,4.56)/14 Bolt (FF,BF shave, Discs, ARB,Artec Truss)/MTR 37X12.5/Corbeau XRS Baja & 5 point retractable harness/Hella Aux lights/tuffy console/killer32 sliders/Evil Twin bumpers, rack and roll cage/WARN 8000/TT Fabworks steering brace/dual batts/custom TC skid plate/ARB fridge
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az chip
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Re: Rough Reverse

Post by az chip »

I have heard you should not mix the two kinds. Rubber or poly, make them all the same kind.
'81 Cherokee Chief 81 WT Chief/MSD 6/Holley Sniper/ Rusty 4" Spring lift/ Bulltear oil adapter/K&P Engineering Oil Filter/ NP 208/ Serehill Light Harness/KC LED Headlights/ Evil Twin Fab Roof Rack and sliders/ Ross mirror mounts.

letank
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Location: SF bay area

Re: Rough Reverse

Post by letank »

Stuka wrote:Checking for engine mounts is easy.

Have the hood open with somebody looking at the engine from the side, NOT from in front, and then while pressing the brake pedal FIRMLY and the parking brake engaged, shift it to reverse. See if the engine torques over. Do the same drive. You can also apply a very small amount of throttle to see if it really moves.

The engine will move a small amount with good mounts, but with bad mounts, its normally pretty obvious that it moves more than it should.
for the one man (person) operation : put front bumper against a utility pole ( a large one), put in D(rive) and while standing on the side give it some gas by pulling the throttle cable, it is always a surprise to see the engine trying to lift itself from the engine bay
Michel
74 wag (349 Kmiles... parked, next step is a rust free body)
85 Gwag (229 Kmiles... the running test lab)

candymancan
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Joined: Tue Mar 22, 2016 11:32 pm

Re: Rough Reverse

Post by candymancan »

HeavyMetalThunder_81 wrote:
KJ Ryu wrote:
candymancan wrote:the transmission has a mount too. Honestly the mounts on these engines are flat solid blocks of rubber.. Unless they rotted comoletetly or the metal part rusted off i doubt engine mounts are bad.. They rarely go bad on these trucks.. Unlike those round hollow mounts on the newer grand cherokees
You must be lucky. I've replaced engine and trans mounts in all three of the FSJs I've driven, usually one of the first things to get done. Polyurethane ones seem to be holding up pretty well.
x2 I've had to replace torn engine mounts on almost every FSJ I've owned. Heck, I've had to replace my trans mount twice on the one I own now.

Interesting. then maybe mine were replaced at ine point.. but they look brand new still.. to me its weird how a solid block of rubber would fall apart unless it got dry rotted or melted from oils and stuff on it.

I guess i take my statement back.
1998 Jeep Grand Cherokee 5.9L Limited 219k
1998 Jeep Grand Cherokee 4.0 I6 laredo 430k
1990 Jeep Grand Wagoneer 155k
1976 Jeep J10.. 85k(repaired)

Elkman06
Posts: 10
Joined: Fri Oct 12, 2012 7:12 pm

Re: Rough Reverse

Post by Elkman06 »

For those of us who wheel real hard, it's a good idea to put a small chain around the frame and engine side of the mountain. If you hit it hard enough the fan can get into the radiator and ruin your day.
Elkman06

Elkman06
Posts: 10
Joined: Fri Oct 12, 2012 7:12 pm

Re: Rough Reverse

Post by Elkman06 »

Auto correct stuff. Mount
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